Maharashtra Board Class 9 Science Chapter 14 Substances in Common Use Solutions

Fill In The Blanks

Question 1. Fill in the blanks.
a. The number of molecules of water of crystallization in washing soda is -
b. The chemical name of baking soda is -
c. - is used in treatment of hyperthyroidism.
d. The chemical name of Teflon is -
Answer:
a. 10
b. Sodium bicarbonate
c. Iodine-123
d. Polytetra fluoroethylene (C\(_{2}\)F\(_{4}\))\(_n\)
In simple words: This question tests knowledge of common chemical substances and their properties, including the water of crystallization in washing soda, the chemical name of baking soda, a radioactive isotope used for hyperthyroidism treatment, and the chemical name of Teflon.

🎯 Exam Tip: Memorizing chemical names, formulas, and common uses of substances is crucial for scoring well in objective-type questions.

Match The Pairs

Question 2. Match the pairs

Group A	Group B
1. Saturated brine	a. sodium metal freed
2. Fused salt	b. basic salt
3. CaOCl\(_{2}\)	c. crystallization of salt
4. NaHCO\(_{3}\)	d. oxidation of colour

Answer:
(1 - c),
(2 - a),
(3 - d),
(4 - b)
In simple words: This question pairs common chemical compounds and states with their related properties or uses, testing understanding of basic chemical concepts and their applications.

🎯 Exam Tip: Understanding the characteristics and common reactions of each substance is key to accurately matching them. Focus on the distinct properties of each compound.

Write Answers To The Following

Question 3. Write answers to the following
a. What is meant by radioactivity?
Answer:
• Elements with a high atomic number such as uranium, thorium, radium have a property of spontaneously emitting invisible, highly penetrating and high energy radiation.
• This property is called radioactivity.
• A substance having this property is called a radioactive substance.
In simple words: Radioactivity is the natural process where unstable heavy elements spontaneously release invisible, high-energy radiation, and substances exhibiting this property are called radioactive.

🎯 Exam Tip: Define radioactivity clearly, mentioning spontaneous emission, high atomic number elements, and the nature of the emitted radiation for a complete answer.

 

b. When is said to be the nucleus unstable?
Answer:
• It is the balance of protons and neutrons in a nucleus which determines whether a nucleus will be stable or unstable.
• Too many neutrons or protons upset this balance disrupting the binding energy from the strong nuclear forces making the nucleus unstable.
In simple words: A nucleus becomes unstable when the ratio or absolute number of protons and neutrons is imbalanced, causing strong nuclear forces to be disrupted and leading to the nucleus breaking down.

🎯 Exam Tip: Focus on the proton-neutron balance and the disruption of binding energy to explain nuclear instability effectively.

 

c. Which diseases are caused by artificial food colours?
Answer:
Diseases like ADHD (Attention Deficit Hyperactivity Disorder) can affect children due to excessive consumption of foods with added food colours.
In simple words: Excessive intake of artificial food colours can lead to health issues in children, particularly affecting attention and behavior, such as Attention Deficit Hyperactivity Disorder (ADHD).

🎯 Exam Tip: Name specific diseases like ADHD and link them directly to the excessive consumption of artificial food colours for a precise answer.

 

d. Where in the industrial field is radioactivity used?
Answer:
Industrial field Radiography
• Internal cracks and voids in cast iron articles and iron solder can be detected with the help of gamma rays.
• For this purpose, isotopes like cobalt-60, iridium-192 are used in the radiography camera.
• This technique is used for detecting flaws in metal work.
Measurement of thickness, density and level
• It is necessary to maintain the required thickness in the manufacture of aluminium, plastic, iron sheets of differing thickness.
• In the manufacturing process, a radioactive substance is placed on one side and an instrument to measure radiation on the other.
• The radiation read by the measuring instrument varies with the thickness of the sheet.
• Material inside a packing can also be examined by the same technique.
Luminescent paint and radio luminescence:
• The radioactive substances radium, promethium, tritium with some phosphor are used to make certain objects visible in the dark, for example, the hands of a clock, and certain other objects.
• Krypton-85 is used in HID (High-Intensity Discharge) lamps while promethium-147 is used in portable X-ray units as the source of beta rays
Use in Ceramic articles:
• Luminous colours are used to decorate ceramic tiles, utensils, plates, etc.
• Earlier uranium oxide was used in these paints.
In simple words: Radioactivity is used in industries for radiography to detect flaws in metal, for measuring the thickness and density of materials, in luminescent paints for visibility in the dark, and in ceramic articles for decorative luminous colours.

🎯 Exam Tip: When listing industrial uses, categorize them (e.g., radiography, thickness measurement, luminescent paints) and provide specific examples of isotopes or applications for each category.

 

e. Write down properties of teflon.
Answer:
Properties of teflon :
• The atmosphere and chemical substances have no effect on Teflon.
• Neither water nor oil will stick to Teflon coated articles.
• High temperatures do not affect Teflon as its melting point is 327 °C.
• Teflon coated articles are easy to clean.
In simple words: Teflon is a chemically inert, non-stick, and heat-resistant material, making it unaffected by atmospheric conditions or chemicals, and easy to clean.

🎯 Exam Tip: Focus on the key properties: chemical inertness, non-stick nature, high melting point, and ease of cleaning, as these are the most significant characteristics of Teflon.

 

f. What type of colours will you use to celebrate ecofriendly Rang Panchami? Why?
Answer:
• We regularly use artificial colours on Rang Panchami.
• The red colour used on Rang Panchami is very dangerous. It contains a high proportion of mercury in it.
• This poses risks like blindness, skin cancer, asthma, itching of the skin, permanent blocking of sweat pores, etc.
• Therefore, it is necessary to use eco-friendly colours.
• We will prepare colours for Rang Panchami from natural resources such as beet root, flowers of flame of forest, spinach, flame tree (gulmohar) and protect your health by using these.
In simple words: To celebrate an eco-friendly Rang Panchami, natural colours made from sources like beetroot, spinach, or flower extracts should be used instead of harmful artificial colours, especially red, which contains mercury and can cause severe health issues like skin irritation, cancer, or blindness.

🎯 Exam Tip: When discussing eco-friendly colours, clearly state the dangers of artificial colours (mentioning specific harmful chemicals like mercury) and then provide examples of natural alternatives and their sources.

 

g. Why has the use of methods like Teflon coating become more common?
Answer:
The use of methods like Teflon coating became more common because of following properties of teflon:
• The atmosphere, rain water and chemical substances have no effect on Teflon.
• Neither water nor oil will stick to Teflon coated articles.
• High temperatures do not affect Teflon as its melting point is 327 °C.
• Teflon coated articles are easy to clean.
• Teflon is a poor conductor of electricity.
In simple words: Teflon coating is common due to its inertness to chemicals and weather, non-stick properties, high heat resistance, ease of cleaning, and electrical insulating capabilities, making it highly versatile and durable for various applications.

🎯 Exam Tip: Emphasize the key benefits of Teflon-coating, such as non-reactivity, non-stick nature, and high thermal stability, as these are the primary reasons for its widespread adoption.

Give A Scientific Explanation

Question 4. Give a scientific explanation
a. Bleaching powder has the odour of chlorine.
Answer:
• Bleaching powder undergoes slow decomposition due to the carbon dioxide in air and chlorine gas is released.
• Bleaching powder gets its property because of this release of chorine gas.
\(CaOCl_2 + CO_2 \)
\( \implies CaCO_3 + Cl_2 \uparrow \)
Bleaching Powder + Carbon dioxide \( \implies \) Calcium Carbonate + Chlorine
In simple words: Bleaching powder smells of chlorine because it slowly reacts with carbon dioxide in the air, decomposing to release chlorine gas, which gives it its characteristic odour and bleaching action.

🎯 Exam Tip: Always include the chemical equation to support your explanation of bleaching powder's decomposition and the release of chlorine gas for full marks.

 

b. The hard water of a well becomes soft on adding washing soda to it.
Answer:
• The hard water from a well or a bore-well becomes soft on adding washing soda and we come to know this from the lather formed on it.
• The hardness of water is due to the presence of chlorides and sulphates of calcium and magnesium in it.
• Na\(_{2}\)CO\(_{3}\) is added to it to soften such water and make it suitable for use.
• The reaction with Na\(_{2}\)CO\(_{3}\) causes the formation of insoluble carbonate salts of magnesium and calcium.
\(MgCl_{2(aq)} + Na_2CO_{3(s)} \)
\( \implies MgCO_{3(s)} + 2 NaCl_{(s)}\)
In simple words: Hard water contains dissolved calcium and magnesium salts; adding washing soda (sodium carbonate) precipitates these metal ions as insoluble carbonates, thus removing the hardness and making the water soft.

🎯 Exam Tip: Explain that washing soda converts soluble calcium and magnesium salts into insoluble carbonates, which then settle out, effectively softening the water. The balanced chemical equation is essential.

 

c. Soap forms a precipitate in hard water.
Answer:
• When soap is mixed with hard water, calcium and magnesium salts of fatty acids are formed.
• These being water insoluble, they form a precipitate and that is why lather is not formed.
In simple words: Soap forms a precipitate in hard water because the calcium and magnesium ions present in hard water react with the fatty acids in soap to form insoluble salts, preventing lather formation.

🎯 Exam Tip: Clearly state that the precipitate is formed by the reaction of soap with calcium and magnesium ions in hard water, creating insoluble salts of fatty acids, which also explains why lather doesn't form.

 

d. The particles of powder are given an electric charge while spraying them to form the powder coating.
Answer:
• Powder coating is a method of applying a layer harder than paint on the surface of an iron object to prevent rusting.
• In this method, a polymer resin, a pigment and some other ingredients are melt, mixed, cooled and ground into a uniform powder.
• This powder is sprayed on the polished metal surface by electrostatic spray deposition (ESD).
• In this method, the particles of the powder are given an electrostatic charge due to which a uniform layer of the powder sticks to the metal surface.
• Then the object is heated in the oven along with the coating.
• A chemical reaction occurs in the layer, resulting in the formation of long cross-linked polymeric chains.
In simple words: Powder coating works by electrostatically charging the powder particles, which causes them to uniformly adhere to the oppositely charged metal surface, ensuring an even and strong bond when heated and cured.

🎯 Exam Tip: Highlight the role of electrostatic charge in ensuring uniform adhesion of the powder particles to the metal surface, which is a key principle of powder coating.

 

e. The aluminium article is used as an anode in the anodising process.
Answer:
• A protective layer is formed naturally on the surface of aluminium metal by reaction with oxygen in air.
• In the anodizing process, this layer is made of the desired thickness. Anodizing is done by electrolysis.
• Dilute Sulphuric acid is taken in the electrolytic cell and the aluminium article is dipped in it as the anode.
• When an electric current is passed, hydrogen gas is released at the cathode and oxygen gas at the anode.
• A reaction with oxygen occurs and a layer of hydrated aluminium oxide is formed on the anode. Therefore, aluminium article is used as an anode in the anodizing process.
In simple words: Aluminium articles are used as the anode in anodising because, during electrolysis, oxygen gas released at the anode reacts with the aluminium to form a thick, protective layer of hydrated aluminium oxide on its surface.

🎯 Exam Tip: Explain that aluminium acts as the anode, where oxidation occurs, causing it to react with oxygen (produced at the anode) to form a durable oxide layer, which is the essence of anodising.

 

f. When the radiation coming out from certain radioactive substance is passed through an electric field, marks are found at three places on the photographic plate placed in its path.
Answer:
(i) When the radiation coming out from certain radioactive substance is passed through an electric field, marks are found at three places on the photographic plate placed in its path. This is because the radiation coming out from radioactive substance are of three types Alpha rays, Beta rays and Gamma rays.
(ii) The rays which get deviated slightly towards negatively charged plate are called alpha rays. They get deviated towards negatively charged plate because they are made of positively charged particles, called as alpha particles (He++).
(iii) The rays which get deviated substantially towards the positively charged plate are called beta rays. They get deviated towards a positively charged plate because they are made of negatively charged particles called as beta particles (e-).
(iv) The rays which do not deviate at all are called gamma rays. They are uncharged electromagnetic radiation. Hence, marks are found at three places on the photographic plate. (For diagram refer Fig. 14.2 from Q. 4(3))
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक विद्युत क्षेत्र से गुजरने वाले रेडियोधर्मी विकिरणों के विचलन को दर्शाता है। इसमें एक लेड ब्लॉक से निकलने वाले विकिरण (अल्फा, बीटा, गामा किरणें) को दो विपरीत आवेशित प्लेटों के बीच से गुजारा जाता है। अल्फा किरणें ऋणात्मक प्लेट की ओर थोड़ी विचलित होती हैं, बीटा किरणें धनात्मक प्लेट की ओर काफी विचलित होती हैं, जबकि गामा किरणें अविचलित सीधी निकल जाती हैं और तीनों एक फोटोग्राफिक प्लेट पर अलग-अलग बिंदु बनाती हैं।
In simple words: Radioactive emissions split into three distinct paths when passed through an electric field because they consist of positively charged alpha particles (deviating slightly towards the negative plate), negatively charged beta particles (deviating significantly towards the positive plate), and neutral gamma rays (passing straight through).

🎯 Exam Tip: Clearly differentiate between alpha, beta, and gamma rays based on their charge, mass, and deviation in an electric field. The degree and direction of deviation are critical points.

 

g. A certain type of ceramic tiles are fixed on the outer layer of a space shuttle.
Answer:
(i) Each shuttle is covered by more than 24,000 of the six-by-six-inch advance ceramic tiles. This tiles withstand high temperatures without decomposing. They are brittle, water-resistant and electrical insulator. Most of the tiles are made of silica fibres, which are produced from high-grade sand (SiO\(_{2}\)).
(ii) Silica is an excellent insulator because it transports heat slowly. When the outer portion of a tile gets hot, the heat takes a long time to work its way down through the rest of the tile to the shuttle's skin. The tiles keep the orbiter's aluminium skin at 350 degrees or less.
(iii) The silica fibers are mixed with water and chemicals, and the mixture is poured into molds, which are zapped in microwave ovens at 2,350°C to fuse the silica fibres. Tiles are too brittle to attach to the orbiter directly.
(iv) The shuttle's skin contracts slightly while in orbit, then expands during re-entry.
(v) In addition, the stresses of launch and re-entry cause the skin to flex and bend. Such motions could easily crack the tiles or shake them off. To keep them in place, workers glue the tiles to flexible felt-like pads, then glue the pads to the orbiter.
In simple words: Ceramic tiles are used on space shuttles because they are made of silica fibers that can withstand extreme re-entry temperatures, act as excellent heat insulators, and are attached with flexible pads to accommodate shuttle skin movements without cracking.

🎯 Exam Tip: Focus on the thermal resistance and insulating properties of silica-based ceramic tiles, and explain how their unique installation method addresses the challenges of temperature and structural stress during space flight.

Write Answers To The Following

Question 5. Write answers to the following
a. Write about artificial food colours, the substances used in them and their harmful effects.
Answer:
(a) Artificial food colour and substances in them.
• Food colours are mixed in most soft drinks and foodstuffs available in the market.
• These food colours are in the form of powders, gels and pastes.
• Food colours are used in domestic as well as commercial products.
• Certain colours and essences are added to ice cream, ice candies, sauce, fruit juices, cold drinks, pickles, jams and jelly.
• Food colours are often found to be added to packaged meat (chicken, mutton), chilli powder, turmeric, sweets and other similar substances so as to give them a good colour.
• Tetrazene, sunset yellow are artificial food colours used extensively.
(b) Harmful effects of artificial food colours
1. Food colours added to pickles, jam and sauce contain small quantities of lead and mercury. These can be harmful for those who consume these products on a regular basis.
2. Diseases like ADHD (Attention Deficit Hyperactivity Disorder) can affect children due to excessive consumption of foods with added food colours.
In simple words: Artificial food colours like Tetrazene and Sunset Yellow are widely used in many food products to enhance appearance but can contain harmful substances like lead and mercury, leading to health issues such as ADHD in children and other adverse effects from regular consumption.

🎯 Exam Tip: When discussing artificial food colours, include common examples like Tetrazene, mention their presence in various foods, and explicitly state the harmful chemicals (lead, mercury) and specific diseases (ADHD) they can cause.

 

b. What is meant by water of crystallization? Give examples of salts with water of crystallization, and their uses.
Answer:
The exact number of water molecules which are chemically bonded to a molecule of a salt within a hydrated crystalline compound is called as water of crystallization are:
Some substances in our daily use which contain water of crystallization are:
• Alum (Potash alum - K\(_{2}\)SO\(_{4}\).Al\(_{2}\)(SO\(_{4}\))\(_3\).24H\(_{2}\)O)
• Borax (Na\(_{2}\)B\(_{4}\)O\(_{7}\).10H\(_{2}\)O)
• Epsom salt (Magnesium sulphate MgSO\(_{4}\).7H\(_{2}\)O)
• Barium chloride (BaCl\(_{2}\).2H\(_{2}\)O)
• Sodium sulphate (Glauber's salt Na\(_{2}\)SO\(_{4}\).10H\(_{2}\)O)
• Blue vitriol (Copper Sulphate - CuSO\(_{4}\).5H\(_{2}\)O)
Uses of these salts are as given below:
(i) Alum (Potash alum - K\(_{2}\)SO\(_{4}\).Al\(_{2}\)(SO\(_{4}\))\(_3\).24H\(_{2}\)O)
• Alum is used in the process of water purification.
• Because of the property of coagulation, the solid impurities in water come together, become heavy and settle to the bottom. As a result, the impure water or muddy above becomes clear.
• Alum powder, found in the spice section of many grocery stores, may be used in pickling recipes as a preservative to maintain fruit and vegetable crispness.
• Alum is used as the acidic component of some commercial baking powders.
• Alum has been used as an after-shave treatment.
(ii) Borax (Na\(_{2}\)B\(_{4}\)O\(_{7}\).10H\(_{2}\)O)
• Borax today is used for many cleaning purposes.
• It is used to make homemade laundry detergent.
• It is added as a cleaning boost to any other detergent.
• It even keeps ants and other pests away.
(iii) Epsom salt (Magnesium sulphate MgSO\(_{4}\).7H\(_{2}\)O)
• Epsom salt is used as a relaxing magnesium bath soak.
• To grow better vegetables - Add a tablespoon of Epsom salt to the soil below a vegetable plant to boost growth.
(iv) Barium chloride (BaCl\(_{2}\).2H\(_{2}\)O)
• In industry, Barium chloride is mainly used in the purification of brine solution in caustic chlorine plants.
• It is also used in the manufacture of heat treatment salts.
(v) Sodium sulphate (Glauber's salt Na\(_{2}\)SO\(_{4}\).10H\(_{2}\)O)
• In the laboratory, anhydrous Sodium sulphate is widely used as an inert drying agent, for removing traces of water from organic solutions.
• Glauber's salt, the decahydrate, is used as a laxative.
(vi) Blue vitriol (Copper sulphate CuSO\(_{4}\).5H\(_{2}\)O)
• Blue vitriol is used in the blood test for diagnosing anaemia.
• Slaked Time is used with blue vitriol in the Bordeaux mixture which is used as a fungicide on fruits like grapes and musk melon.
In simple words: Water of crystallization refers to the specific number of water molecules chemically bonded within a crystalline salt structure; examples include alum (used for water purification), borax (for cleaning), Epsom salt (for baths and plant growth), barium chloride (in chemical manufacturing), sodium sulphate (as a laxative), and blue vitriol (for medical tests and fungicides).

🎯 Exam Tip: Define water of crystallization clearly, list at least 3-4 common examples with their chemical formulas (including water molecules), and provide at least one key use for each example to ensure a comprehensive answer.

 

c. Write briefly about the three methods of electrolysis of sodium chloride.
Answer:
• When an electric current is passed through a saturated solution of sodium chloride (brine) it is electrolysed and hydrogen gas is released at the cathode while chlorine gas is released at the anode.
• This method is used for production of chlorine gas. In this method an important basic compound NaOH is formed in the cell.
Chemical reaction
\(2NaCl + 2H_2O \)
\( \implies 2NaOH + Cl_2 \uparrow + H_2 \uparrow \)
• When salt is heated to a high temperature (about 800 °C), it melts. This is called the fused state of the salt.
In simple words: Electrolysis of sodium chloride involves passing an electric current through either its saturated aqueous solution (brine) to produce hydrogen, chlorine, and NaOH, or through its molten (fused) state at high temperatures to produce chlorine gas and liquid sodium metal.

🎯 Exam Tip: Distinguish between the electrolysis of aqueous sodium chloride (brine) and molten sodium chloride (fused state), highlighting the products formed at the anode and cathode for each method, along with the relevant chemical equations.

Write The Uses

Question 6. Write the uses.
a. Anodizing
b. Powder coating
c. Radioactive substances
d. Ceramic
Answer:
(a) Anodizing: Anodizing is done on aluminum cooking utensils like griddles and cookers.
(b) Powder coating : Powder coating is done on iron objects to prevent rusting. Also, on Plastic and Medium density fibre (MDF) board, to make them highly durable, hard and attractive.
(c) Radioactive substances:
(I) Industrial field:
(i) Industrial Radiography : Internal cracks and voids in cast iron articles and iron solder can be detected with the help of gamma rays. For this purpose, isotopes like cobalt-60, iridium-192 are used in the radiography camera. This technique is used for detecting flaws in metal work.
(ii) Measurement of thickness, density and level: It is necessary to maintain the required thickness in the manufacture of aluminium, plastic, iron sheets of differing thickness. In the manufacturing process, a radioactive substance is placed on one side and an instrument to measure radiation on the other. The radiation read by the measuring instrument varies with the thickness of the sheet. Material inside a packing can also be examined by the same technique.
(iii) Luminescent paint and radioluminescence:
The radioactive substances radium, promethium, tritium with some phosphor are used to make certain objects visible in the dark, for example, the hands of a clock, and certain other objects. Krypton-85 is used in HID (High Intensity Discharge) lamps while promethium-147 is used in portable X-ray units as the source of beta rays.
Use in Ceramic articles – Luminous colours are used to decorate ceramic tiles, utensils, plates, etc. Earlier uranium oxide was used in these paints.
(II) Field of agriculture :
• The genes and chromosomes that give seeds properties like fast growth, higher productivity, etc. can be modified by means of radiation.
• The radioactive isotope cobalt-60 is used for food preservation.
• Onions, potatoes are irradiated with gamma rays from cobalt-60 to prevent their sprouting.
• Strontium-90 is used as a tracer in the research on various crops.
(III) Medical science:
• Polycythemia : The red blood cell count increases in the disease polycythemia. Phosphorus-32 is used in its treatment.
• Bone cancer : Strontium-89, strontium-90, samarium-153 and radium-223 are used in the treatment of bone cancer.
• Hyperthyroidism : Enlargement of thyroid gland, weight loss in spite of appetite, insomnia are the symptoms of hyperthyroidism.
• It occurs due to overproduction of hormones by the thyroid gland. Iodine-123 is used in the treatment of hyperthyroidism.
• Tumour detection : Boron-10, iodine-131, cobalt-60 are used in treatment of brain tumour, while arsenic-74 is used in detection of small tumours in the body.
(d) Ceramic : Pots made by a potter, Mangalore roofing tiles, construction bricks, pottery, terracotta articles are some examples of common ceramic articles that we see around.
In simple words: Anodizing is used to protect aluminium utensils; powder coating prevents rust and adds durability to various surfaces; radioactive substances find extensive use in industrial radiography, thickness measurement, agriculture (food preservation, crop research), and medical applications (cancer treatment, hyperthyroidism diagnosis); and ceramics are used for pottery, tiles, and construction bricks due to their heat resistance and durability.

🎯 Exam Tip: For each item, provide at least two distinct uses. For radioactive substances, categorize their applications (industrial, agricultural, medical) and give specific examples of isotopes and their functions within each category.

Write The Harmful Effects

Question 7. Write the harmful effects
a. Artificial dye
b. Artificial food colour
c. Radioactive substances
d. Deodorant
Answer:
(a) Artificial dye:
• Dyeing hair can have adverse effects like hair fall, damage to hair texture, burning of skin, adverse effect on eyes, etc.
• Lipstick contains a dye named carmine. It does not affect lips but causes stomach disorders.
• Excessive use of plants for making natural dyes results in deterioration of the environment.
(b) Artificial food colour:
• Food colours added to pickles, jams and sauces contain small quantities of lead and mercury. These can be harmful for those who consume these products on a regular basis.
• Diseases like ADHD (Attention Deficit Hyperactivity Disorder) can affect children due to excessive consumption of foods with added food colours.
(c) Radioactive substances :
• The central nervous system is affected by radioactive radiations.
• Hereditary defects are generated by bombardment of radiation on D.N.A in the body.
• Radioactive radiation can penetrate the skin, and causes diseases like skin cancer, leukemia.
• The radioactive pollutants created due to explosions enter the body through air and it is difficult to control them.
• The radioactive pollutants released in the sea enter the bodies of fishes and through them enter the human body.
• The radioactive paint on the watch can cause cancer.
• The radioactive isotopes strontium-90 can enter the body through plants, fruits, flowers, cereals, milk, etc. and cause diseases like bone cancer, leukemia.
(d) Deodorant:
• Aluminium-Zirconium compounds are the most harmful chemicals in the deodorant. Disorders like headache, asthma, respiratory disorders, heart disease are likely to occur without our knowledge.
• There is a possibility of various skin disorders and also skin cancer due to the aluminium chlorohydrates.
In simple words: Artificial dyes can cause hair and skin damage, and specific dyes like carmine in lipstick can lead to stomach disorders; artificial food colours with lead and mercury can cause ADHD and other health issues; radioactive substances can damage DNA, cause cancer, and affect the central nervous system; and deodorants containing aluminium-zirconium compounds or chlorohydrates may lead to headaches, asthma, heart disease, and skin cancer.

🎯 Exam Tip: For each category, provide specific harmful effects and, if applicable, name the harmful chemicals or isotopes involved to demonstrate a thorough understanding of the risks.

Question 8. Write the chemical formula Bleaching powder, common salt, baking soda, washing soda
Answer:

Common name	Chemical name
Bleaching powder	CaOCl\(_{2}\)
Common salt	NaCl
Baking soda	NaHCO\(_{3}\)
Washing soda	Na\(_{2}\)CO\(_{3}\).10 H\(_{2}\)O

In simple words: This question asks for the chemical formulas of common household substances like bleaching powder (CaOCl\(_{2}\)), common salt (NaCl), baking soda (NaHCO\(_{3}\)), and washing soda (Na\(_{2}\)CO\(_{3}\).10H\(_{2}\)O).

🎯 Exam Tip: Accurately writing the chemical formula for each substance, including the water of crystallization for washing soda, is essential for full credit.

 

Question 9. Explain what you see in the following picture
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक व्यक्ति को स्प्रे गन का उपयोग करके एक वस्तु पर पाउडर कोटिंग करते हुए दर्शाता है। वस्तु को एक स्टैंड पर रखा गया है और स्प्रे गन से निकल रहे रंगीन पाउडर के कण वस्तु की सतह पर समान रूप से चिपक रहे हैं, जो पाउडर कोटिंग प्रक्रिया के इलेक्ट्रोस्टैटिक स्प्रे डिपोजिशन चरण को दर्शाता है।
Powder coating
Answer:
1. This picture shows powder coating of the given object. Powder coating is a method of applying a layer harder than paint on the surface of an iron object to prevent rusting.
2. In this method, a polymer resin, a pigment and some other ingredients are melt mixed, cooled and ground into a uniform powder.
3. This powder is sprayed on the polished metal surface by electrostatic spray deposition (ESD).
4. In this method, the particles of the powder are given an electrostatic charge due to which a uniform layer of the powder sticks to the metal surface.
5. Then the object is heated in the oven along with the coating.
6. A chemical reaction occurs in the layer, resulting in the formation of long cross-linked polymeric chains.
7. This powder coating is highly durable, hard and attractive. Powder coating can be done on plastic and medium density fibre (MDF) board in day to day use as well.
In simple words: The picture illustrates powder coating, a process where electrostatically charged powder, made from polymer resin and pigments, is sprayed onto a metal object, then heated to form a durable, rust-preventing, and attractive layer of cross-linked polymeric chains.

🎯 Exam Tip: When explaining powder coating, detail the steps from powder preparation and electrostatic spraying to heating and the formation of cross-linked polymeric chains. Emphasize the durability and protective qualities of the resulting coating.

Class 9 Science Chapter 14 Substances In Common Use Intext Questions And Answers

Can You Recall?

Question 1. What are detergents?
Answer:
• Detergent is a water-soluble cleansing agent which combines with impurities and dirt to make them more soluble, and differs from soap in not forming a scum with the salts in hard water.
• Today, detergents are more likely to be a mixture of synthetic chemicals and additives cooked up in a huge chemical plant and, unlike traditional soap, they're generally liquids rather than solids.
• Detergents are used in everything from hair shampoo and clothes, washing powder to shaving foam and stain removers.
• The most important ingredients in detergents are chemicals called surfactants - a word made from bits of the words surface-active agents.
In simple words: Detergents are water-soluble cleaning agents, typically synthetic chemicals containing surfactants, that effectively remove dirt by making impurities more soluble and, unlike soap, do not form scum in hard water.

🎯 Exam Tip: Define detergents by their key characteristics: water-soluble, cleansing agents, synthetic composition, and the presence of surfactants, emphasizing their ability to clean effectively even in hard water.

Question 2. What are the important substances that we use in day to day life? For what purposes do we use them?
Answer:Some of the substances we use in our day to day life and the purpose of using them are as follows: Toothpaste: for cleaning teeth and maintaining hygienic conditions of mouth.
Soap: for bathing and maintaining hygienic conditions of body.
Natural and artificial fibers: we wear them as clothes to protect our body and many other purposes.
Washing powder: for cleaning clothes. Vegetables, fruits and food grains: they provide us with necessary vitamins, minerals and carbohydrates required for proper functioning of body.
Water: very important for our survival and many other functions of day to day life.
Metals: for making buildings, bridges, roads, vehicles, trains, ships, airplanes, utensils etc.
Acids, bases and salts: used for various purposes, for example, Sodium chloride which is used as common salt, a very necessary ingredient of our daily food without which our food is tasteless.
In simple words: We use various substances like toothpaste for hygiene, soap for bathing, fibers for clothing, washing powder for cleaning, food for nourishment, water for survival, metals for construction, and acids, bases, and salts for diverse applications, including cooking.

🎯 Exam Tip: Focus on listing a variety of substances and their primary functions for a comprehensive answer, covering different aspects of daily life.

Question 3. How are the various substances in day to day use classified from the scientific point of view?
Answer:The various substances in day to day use are classified from the scientific point of view as elements, compounds, mixtures, metals, non-metals, acids, bases and salts.
In simple words: From a scientific perspective, everyday substances are categorized as elements, compounds, mixtures, metals, non-metals, acids, bases, and salts based on their chemical composition and properties.

🎯 Exam Tip: Remember the fundamental scientific classifications to accurately categorize common substances in your answer.

Question 4. Which chemicals and apparatus will you use in the laboratory for making soap?
Answer:For making soap in laboratory following chemicals and apparatus are used :
Chemicals: Vegetable oil (coconut oil, castor oil, soya bean oil etc.)
Sodium hydroxide (NaOH)
Salt (Sodium chloride NaCl)
Apparatus :
500 ml glass beaker
Burner
Flat glass tray
Knife
Soaps are essential to personal and public health. They safely remove germs, soils and other contaminants and help us to stay healthy and make our surroundings more pleasant. Soaps are made from fats and oils or their fatty acids.
Take about 20 ml of any vegetable oil (coconut oil, castor oil, soybean oil etc.) in a beaker. Put about 30 - 35 ml of NaOH in it and heat and stir the mixture till a paste is formed. Now add a little salt. Stir again and allow the mixture to cool in a flat glass tray, on cooling it solidifies. Take a knife and cut it in soap bars as per the size required.
In simple words: To make soap in a lab, you need vegetable oil, sodium hydroxide (lye), and salt as chemicals, along with a beaker, burner, glass tray, and knife as apparatus. The process involves heating oil with lye to form a paste, then adding salt and cooling to solidify it into soap.

🎯 Exam Tip: List both the specific chemicals and laboratory equipment required, and provide a brief, step-by-step description of the soap-making process.

Question 5. What are salts?
Answer:- Inorganic substances occur naturally in the form of salts rather than acids or bases.
- The ionic compounds which do not contain H+ and OH ions and contain only one kind of cation and anion are called simple salts.
- For example, Na2SO4, K3PO4, CaCl2.
- The sea is said to be a rich source of salts. In fact, the sea is a rich source of several salts of various elements such as chlorine, sodium, magnesium, potassium, calcium, bromine.
- The important salts found in sea water are sodium chloride, magnesium chloride, magnesium sulphate, potassium chloride, calcium carbonate and magnesium bromide.
In simple words: Salts are ionic compounds that don't have H+ or OH- ions, found naturally, often in seawater, and are composed of a single type of cation and anion.

🎯 Exam Tip: Define salts by their ionic composition and absence of H+/OH- ions, and provide common examples to illustrate your answer.

Answer the following questions:

Question 1. How is it determined whether a substance is acidic, basic or neutral?
Answer:- In the pH scale, the pH of solutions varies from 0 to 14 in accordance with the strength of the acids or base.
- The pH scale shows different colours at different values of pH. Colour from dark red to yellow or from pH value 0 to 6 indicates the substances are acidic.
- Colour from light blue to violet or from pH value 8 to 14 indicates the substances are basic.
- Green colour or pH value 7 indicates the substances are neutral.
In simple words: A substance's acidity, basicity, or neutrality is determined using the pH scale, where pH 0-6 (dark red to yellow) indicates acidic, pH 8-14 (light blue to violet) indicates basic, and pH 7 (green) indicates neutral.

🎯 Exam Tip: Clearly explain the pH scale range and the corresponding color indications for acidic, basic, and neutral substances.

Question 2. A sweets shop looks attractive because of the colourful sweets displayed there. Which colours are used in these substances?
Answer:- Food colours and essences are used in sweets to make them colourful and tasty.
- These food colour are in the form of powders, gels and pastes.
- Food colours are natural as well as artificial.
- The food colours prepared from seeds, beetroot, flowers and fruit concentrate are natural.
- Tetrazene, sunset yellow are artificial food colours used extensively.
In simple words: Sweets get their appealing colors from both natural food colors derived from seeds, beetroot, flowers, and fruit concentrates, and artificial food colors like tetrazene and sunset yellow, which also enhance taste.

🎯 Exam Tip: Distinguish between natural and artificial food colors, providing examples of each, and note their forms (powders, gels, pastes).

Question 3. Make a list of substances in day to day use in accordance with their pH value (O to 14).
Answer:

Substances	Original colour (of the solution)	Colour on addition of universal indicator	pH value	Nature
Kokam extract	Pink	Orange	4.5	Acidic
Palak extract	Green	Light green	95	Basic
Aerated drink	Brown	Greenish yellow	6.0	Acidic
Tomato juice	Red	Orange	4.1	Acidic
Dilute HNO	Colourless	Orange red	3	Acidic
Dilute KOH	Colourless	Violet	13	Basic
Prepared tea	Brown	Orange yellow	6	Acidic
Ginger juice + Honey	Brown	Yellow	5.5	Acidic
Butter milk	White	Greenish yellow	6.5	Acidic

In simple words: This table categorizes common substances by their original color, their color change with a universal indicator, their pH value (on a 0-14 scale), and their resulting acidic or basic nature.

🎯 Exam Tip: For tables, ensure all columns are correctly labeled and the data for each substance (original color, indicator color, pH, and nature) is accurately presented.

Question 4. A doctor gives you medicines when you fall ill. What are the medicines made from?
Answer:- Long before pure chemicals were manufactured in labs, people used plants for medicine.
- There are over a hundred active ingredients derived from plants for use as drugs and medicines.
- The emergence of synthetic chemistry in the 1800s opened up new avenues for scientific research into drugs.
- Many chemists tried to locate medically active ingredients in plants (for instance the important malaria remedy quinine), and subsequently tried to make those substances in the laboratory in order to become independent of plant supplies.
- At the same time, a new industry developed as scientists developed processes to synthesise new chemicals on a large scale.
- New production methods developed in the late 1800s and early 1900s made it easier to standardise, package and transport medicines.
In simple words: Medicines are historically derived from plants, with over a hundred active ingredients still used from them. Modern medicine also relies on synthetic chemistry, where active compounds are either isolated from plants and then synthesized or new chemicals are developed in laboratories for standardized production.

🎯 Exam Tip: Highlight both the historical use of plants and the modern role of synthetic chemistry in medicine production, emphasizing standardization and large-scale manufacturing.

Question 5. What problems do you get after playing colours on Rang Panchami? Why?
Answer:- After playing colours on Rang Panchami we may get problems such as risks of blindness, skin cancer, asthma, itching of the skin, permanent blocking of sweat pores etc.
- This is because the colours used in rang panchami specially the red colour is very dangerous.
- It contains a high proportion of mercury in it.
In simple words: Playing with Rang Panchami colors, especially red, can cause health issues like blindness, skin cancer, asthma, itching, and blocked sweat pores due to the high mercury content and other harmful chemicals in artificial dyes.

🎯 Exam Tip: Focus on the specific health hazards associated with artificial colors, particularly the red color, and mention the harmful substance (mercury) responsible.

Question 6. Which colours will you use to prevent the occurrence of these problems?
Answer:- To prevent the occurrence of these problem, instead of using artificial colours, natural colours should be used.
- Natural colours are prepared from natural resouroes such as beet root, flowers of flame of forest, spinach, flame tree (gulmohar).
In simple words: To avoid health problems from artificial colors during Rang Panchami, natural colors should be used, which are derived from sources like beetroot, flame of forest flowers, spinach, and gulmohar.

🎯 Exam Tip: Emphasize the shift to natural colors and provide concrete examples of natural sources for these colors.

Question 7. What problem do you have on painting the house and furniture?
Answer:- On painting the house and furniture with artificial colours which are dangerous, we may get problems such as risks of blindness, skin cancer, asthma, itching of the skin, permanent blocking of sweat pores, etc.
- This is because the colours contain a high proportion of mercury in it.
In simple words: Painting houses and furniture with dangerous artificial colors can lead to health problems like blindness, skin cancer, asthma, itching, and blocked sweat pores, primarily because these colors often contain high levels of mercury.

🎯 Exam Tip: Connect the use of artificial colors in paint to similar health hazards as in Rang Panchami colors, specifically mentioning mercury content.

Question 8. What is the property of Teflon because of which it is used in non-stickware?
Answer:Following are the properties of teflon because of which it is used in nonstick cookware.
- The atmosphere and chemical substances have no effect on Teflon.
- Neither water nor oil will stick to Teflon coated non-stickware.
- High temperatures do not affect Teflon as its melting point is 327 °C.
- Teflon coated non-stickware are easy to clean.
In simple words: Teflon is used in non-stickware due to its resistance to atmospheric and chemical substances, its non-stick properties against water and oil, its high melting point (327 °C), and its ease of cleaning.

🎯 Exam Tip: List the key properties of Teflon that make it suitable for non-stick applications, such as chemical inertness, non-adherence, and thermal stability.

Answer the following questions:

Question 1. What is the strip shown below? What is it used for?
Answer:The strip shown is pH metre scale. It is used to determined pH of solutions.
In simple words: The strip shown is a pH meter scale, used to measure the pH (acidity or alkalinity) of solutions.

🎯 Exam Tip: Identify the strip correctly as a pH meter scale and state its primary function: determining the pH of solutions.

Question 2. Prepare saturated solutions of given salts and put 2-3 drops of the universal indicator in them and note your observations in the table below:
Answer:

Salt	Original colour (of the solution)	Colour on addition of universal indicator	pH value	Nature
Table salt	Colorless	Green	7	Neutral
Soap	White	Blue	9	Alkaline (mildly)
Washing soda	White	Dark blue	11	Alkaline (strongly)
Baking soda	White	Dark green	8	Alkaline (slightly)
Baking powder	White	Dark green	8.5	Alkaline (slightly)
POP	White	Green	7	Neutral

In simple words: This table demonstrates the pH of various salt solutions using a universal indicator, showing their original color, color change with the indicator, pH value, and whether they are neutral or alkaline (mildly, slightly, or strongly).

🎯 Exam Tip: When presenting experimental observations in a table, ensure accuracy in pH values and corresponding nature (acidic, basic, neutral) for each substance.

Class 9 Science Chapter 14 Substances in Common Use Additional Important Questions and Answers

Select the correct option:

Question 1. Baking soda is ..............
(a) non-metallic
(b) metallic
(c) acidic
(d) basic
Answer: (d) basic
In simple words: Baking soda is basic in nature, meaning it has a pH greater than 7.

🎯 Exam Tip: Remember that baking soda (sodium bicarbonate) is a mild base, which is why it reacts with acids and is used as an antacid.

Question 2. During electrolysis of NaCl in the fused state .............. is formed at cathode.
(a) sodium
(b) oxygen
(c) oxalic acid
(d) butyric acid
Answer: (a) sodium
In simple words: When molten sodium chloride undergoes electrolysis, sodium metal is produced at the cathode.

🎯 Exam Tip: In the electrolysis of fused NaCl, sodium ions (Na+) are reduced at the cathode, forming sodium metal, while chloride ions (Cl-) are oxidized at the anode to form chlorine gas.

Question 3. .............. is known as chloride of lime.
(a) Calcium carbonate
(b) Sodium bicarbonate
(c) Sodium chloride
(d) Bleaching powder
Answer: (d) Bleaching powder
In simple words: Bleaching powder is chemically known as chloride of lime.

🎯 Exam Tip: Know the common names and chemical names/formulas for important compounds like bleaching powder (calcium oxychloride).

Question 4. Salt obtained from certain type of rock is called ..............
(a) hard salt
(b) rock salt
(c) stone salt
(d) pure salt
Answer: (b) rock salt
In simple words: Salt extracted from specific rock formations is referred to as rock salt.

🎯 Exam Tip: Understand the origin and terminology of different types of salts, such as rock salt, which is mined from deposits.

Question 5. The ..............% aqueous solution of salt is called brine.
(a) 25
(b) 60
(c) 30
(d) 50
Answer: (a) 25
In simple words: A 25% aqueous solution of salt is known as brine.

🎯 Exam Tip: Memorize the concentration definition for common solutions like brine, which is a saturated salt solution.

Question 6. The molecular formula for baking soda is ..............
(a) Na2CO3
(b) NaHCO3
(c) Na2SO4
(d) NaNO3
Answer: (b) NaHCO3
In simple words: The molecular formula for baking soda is NaHCO3.

🎯 Exam Tip: Ensure you know the chemical formulas for common substances like baking soda (sodium bicarbonate).

Question 7. Bleaching powder is also called ..............
(a) Calcium oxygen chlorine
(b) Calcium oxychloride
(c) Calcium hydroxide
(d) Calcium oxalate
Answer: (b) Calcium oxychloride
In simple words: Bleaching powder is also known by its chemical name, calcium oxychloride.

🎯 Exam Tip: Link common names to their correct chemical nomenclature, as this is a frequent source of questions.

Question 8. NaHCO3 is also called as ..............
(a) Sodium carbonate
(b) Sodium bicarbonate
(c) Sodium carbon oxide
(d) Sodium chloride
Answer: (b) sodium bicarbonate
In simple words: NaHCO3 is chemically named sodium bicarbonate, also known as baking soda.

🎯 Exam Tip: Recognize the chemical formula NaHCO3 as sodium bicarbonate and its common name, baking soda.

Question 9. Molecular formula for Magnesium bromide is ..............
(a) MgBr
(b) Mg2Br
(c) Mg2Br2
(d) MgBr2
Answer: (d) MgBr2
In simple words: The molecular formula for Magnesium bromide is MgBr2.

🎯 Exam Tip: Apply the rules of chemical nomenclature and valency to correctly write molecular formulas for ionic compounds.

Question 10. The molten state of NaCl is also called as ..............
(a) solid state
(b) semi-solid
(c) gaseous state
(d) fused state
Answer: (d) fused state
In simple words: The molten state of sodium chloride (NaCl) is referred to as the fused state.

🎯 Exam Tip: Understand the terminology used to describe states of matter for compounds, particularly "fused state" for molten ionic solids.

Question 11. Substance used to make hard water soft is ..............
(a) Na2CO3.10H2O
(b) Na2CO3.H2O
(c) NaCO3.10H2O
(d) NaCO3.H2O
Answer: (a) Na2CO3.10H2O
In simple words: Washing soda, with the chemical formula Na2CO3.10H2O, is used to soften hard water.

🎯 Exam Tip: Know the chemical formula of washing soda and its application in water softening due to its ability to precipitate calcium and magnesium ions.

Question 12. The fixed number of molecules of water in alum is ..............
(a) 24
(b) 10
(c) 7
(d) 2
Answer: (a) 24
In simple words: Alum contains 24 molecules of water of crystallization.

🎯 Exam Tip: Recall the specific number of water molecules in common hydrated salts like alum (potash alum, K2SO4.Al2(SO4)3.24H2O).

Question 13. Chlorine gas is a strong .............. agent.
(a) reducing
(b) oxidising
(c) neutral
(d) acidic
Answer: (b) oxidising
In simple words: Chlorine gas is a powerful oxidizing agent.

🎯 Exam Tip: Understand the chemical properties of common gases; chlorine's high electronegativity makes it a strong oxidizing agent.

Question 14. Bleaching powder is .............. in colour.
(a) brownish red
(b) yellowish-white
(c) pinkish brown
(d) greenish blue
Answer: (b) yellowish-white
In simple words: Bleaching powder is typically yellowish-white in color.

🎯 Exam Tip: Be aware of the physical characteristics, such as color, of common chemical compounds.

Question 15. Soap is .............. in nature.
(a) acidic
(b) basic
(c) neutral
(d) fuming
Answer: (b) basic
In simple words: Soap is basic in nature.

🎯 Exam Tip: Recall that soaps are salts of fatty acids, formed from a strong base and a weak acid, making them basic in aqueous solutions.

Question 16. Melting point of NaCl is ..............
(a) 400°C
(b) 100°C
(c) 800°C
(d) 600°C
Answer: (c) 800°C
In simple words: The melting point of sodium chloride (NaCl) is 800°C.

🎯 Exam Tip: Remember key physical properties like the melting point of common ionic compounds such as NaCl.

Question 17. Rock salt is .............. in colour.
(a) black
(b) white
(c) brown
(d) blue
Answer: (c) brown
In simple words: Rock salt typically appears brown in color.

🎯 Exam Tip: Note that impurities often give rock salt its characteristic brownish color, unlike refined table salt.

Question 18. Strong odour in swimming pool is due to ..............
(a) chlorine gas
(b) impurities
(c) calcium carbonate
(d) calcium hydroxide
Answer: (a) chlorine gas
In simple words: The strong odor often found in swimming pools is caused by chlorine gas, used for disinfection.

🎯 Exam Tip: Understand that chlorine is added to swimming pools as a disinfectant, and its characteristic smell is a result of its presence.

Question 19. Molecular formula of sodium bicarbonate is ..............
(a) NaHCO3
(b) Na2HCO3
(c) Na2HCO2
(d) NaHCO2
Answer: (a) NaHCO3
In simple words: The molecular formula for sodium bicarbonate is NaHCO3.

🎯 Exam Tip: Accurately write molecular formulas based on the names of chemical compounds, paying attention to valencies and subscripts.

Question 20. Soap is .............. in nature.
(a) radioactive
(b) natural
(c) acidic
(d) basic
Answer: (d) basic
In simple words: Soap has a basic nature.

🎯 Exam Tip: Reiterate that soap is basic due to its composition as a salt of a strong base and a weak acid.

Question 21. The molecular formula for Magnesium bromide is ..............
(a) MgBr
(b) MgBr2
(c) Mg2Br2
(d) Mg2Br
Answer: (b) MgBr2
In simple words: The molecular formula for Magnesium bromide is MgBr2.

🎯 Exam Tip: Ensure correct formula writing by balancing the charges of magnesium (Mg2+) and bromide (Br-) ions.

Fill in the blanks and rewrite the complete statements:

(1) 25% of NaCl is known as ..............
(2) .............. gas is released when bleaching powder is added to water.
(3) Washing soda is as it absorbs moisture if left exposed to air.
(4) .............. is used to make hard water soft.
(5) Molecular formula for Alum is ..............
(6) .............. is used in blood test for diagnosing anaemia.
(7) High grade of .............. and .............. are used as raw material to manufacture bathing soap.
(8) Pickles, jams and sauce contain small quantities of .............. and ..............
(9) Excessive consumption of foods with added food colours leads to diseases like ..............
(10) Melting point of Teflon is ..............
(11) Anodizing is done by ..............
(12) The red blood cell count increases in the disease ..............
(13) Magnesium sulphate (MgSO4.7H20) is also called ..............
Answer:
(1) Brine
(2) Chlorine
(3) hygroscopic
(4) Na2CO3 (Washing soda)
(5) K2SO4.Al2(SO)3.24H2O
(6) Blue Vitriol
(7) fats, oils
(8) lead, mercury
(9) ADHD (Attention Deficit Hyperactivity Disorder)
(10) 327°C
(11) Electrolysis
(12) Polycythemia
(13) Epsom salt
(14) Soap
In simple words: The blanks are filled with key chemical terms and properties: 25% NaCl is brine, chlorine is released from bleaching powder in water, washing soda is hygroscopic and softens hard water, alum's formula is K2SO4.Al2(SO4)3.24H2O, blue vitriol diagnoses anemia, bathing soap uses high-grade fats and oils, pickles/jams contain lead and mercury, excess food colors cause ADHD, Teflon's melting point is 327°C, anodizing uses electrolysis, polycythemia increases red blood cell count, and magnesium sulfate is Epsom salt.

🎯 Exam Tip: For fill-in-the-blanks, recall specific facts, chemical formulas, common names, and direct applications of substances covered in the chapter.

State whether the following statements are true or false. Correct the false statements.

(1) Bleaching powder is used in preparation of chloroform which is used as an anaesthetic.
(2) On addition of universal indicator the colour of table salt changes to pink.
(3) Borax is Na2B4O7.9H2O.
(4) Boron -10 is used to cure bone cancer.
(5) Clinical deo contains 20 to 25% of aluminium.
(6) NaHCO3 is sodium carbonate.
(7) Soap is acidic in nature.
(8) Baking powder is neutral in nature.
(9) POP is crystalline in nature.
(10) pH value of universal indicator is 0 - 7.
(11) Sodium chloride is formed by neutralization reaction between sodium hydroxide and calcium carbonate.
(12) Boiling point of NaCl is 800 °C.
(13) Molten state of NaCl is also called as solid state.
(14) Mineral halite is an example of Rock Salt.
(15) Sodium bicarbonate is used to reduce acidity.
(16) Bleaching powder is also called as chloride of lime.
(17) Bleaching powder is obtained by reaction of chlorine gas with slaked lime.
(18) Bleaching powder available in market is classified on the basis of colour.
(19) The hard water becomes soft on adding baking soda (NaHCO3)
Answer:
(1) True
(2) False. On addition of universal indicator the colour of table salt changes to green.
(3) False. Borax is Na2B4O7.9H2O
(4) False. Boron - 10 is used in treatment of brain tumour.
(5) True
(6) False. NaHCO3 is sodium bicarbonate.
(7) False. Soap is basic in nature.
(8) False. Baking powder is basic in nature.
(9) False. POP is amorphous in nature.
(10) False. pH value of universal indicator is 0 -14.
(11) False. Sodium chloride is formed by a neutralization reaction between sodium hydroxide and hydrochloric acid.
(12) False. Melting point of NaCl is 800°C.
(13) False. Molten state of NaCl is also called as fused state.
(14) True
(15) True
(16) True
(17) True
(18) False. Bleaching powder available in market is classified on the basis of percentage of chlorine present in it.
(19) False. Hard water becomes soft on adding washing soda (Na2CO3.10H2O)
In simple words: This section corrects false statements about chemical properties and uses, clarifying that table salt with universal indicator turns green, boron-10 treats brain tumors, baking soda is NaHCO3, soap and baking powder are basic, POP is amorphous, pH scale is 0-14, NaCl is formed from NaOH and HCl, its melting point is 801°C, molten NaCl is fused state, and hard water softens with washing soda, not baking soda.

🎯 Exam Tip: Pay close attention to chemical formulas, common names, reactions, and properties to accurately determine true/false statements and provide correct alternatives.

Name the following:

Question 1. Important salts found in sea water.
Answer:Magnesium chloride, Potassium chloride
In simple words: Important salts found in seawater include magnesium chloride and potassium chloride.

🎯 Exam Tip: List common ionic salts (compounds) that are abundant in seawater.

Question 2. Chemical used in preparation of breads and cakes to make them soft.
Answer:Sodium bicarbonate
In simple words: Sodium bicarbonate is the chemical used to make breads and cakes soft.

🎯 Exam Tip: Identify baking soda (sodium bicarbonate) as the leavening agent responsible for softness in baked goods.

Question 3. Gas liberated when bleaching powder is added to CO2 gas.
Answer:Chlorine (Cl2) gas.
In simple words: When bleaching powder reacts with CO2 gas, chlorine gas (Cl2) is liberated.

🎯 Exam Tip: Remember the reaction of bleaching powder with carbon dioxide, which releases chlorine gas, known as "available chlorine."

Question 4. Salt used in refining petroleum
Answer:Sodium carbonate (Na2CO3)
In simple words: Sodium carbonate (Na2CO3) is a salt used in the refining of petroleum.

🎯 Exam Tip: Note specific industrial applications of common salts, such as sodium carbonate in petroleum refining.

Question 5. Chemical formula of bleaching powder
Answer:CaOCl2
In simple words: The chemical formula for bleaching powder is CaOCl2.

🎯 Exam Tip: Precisely recall the chemical formula for bleaching powder (calcium oxychloride).

Question 6. The chemical formula of Sodium hydrogen carbonate.
Answer:NaHCO3
In simple words: The chemical formula for Sodium hydrogen carbonate is NaHCO3.

🎯 Exam Tip: Know the chemical formula for sodium hydrogen carbonate, also known as sodium bicarbonate or baking soda.

Question 7. Nature of soap.
Answer:Basic
In simple words: Soap is basic in nature.

🎯 Exam Tip: Confirm that soap solutions are basic due to hydrolysis of the fatty acid salts.

Question 8. Molecular formula for Magnesium bromide
Answer:MgBr2
In simple words: The molecular formula for Magnesium bromide is MgBr2.

🎯 Exam Tip: Correctly determine the molecular formula for magnesium bromide by ensuring charge balance (Mg2+ and Br-).

Question 9. Melting point of NaCl
Answer:800 °C
In simple words: The melting point of NaCl is approximately 800 °C.

🎯 Exam Tip: Recall the specific melting point of sodium chloride, a common ionic compound.

Question 10. Two examples of Rock Salt
Answer:Mineral halite and Himalayan rock salt.
In simple words: Mineral halite and Himalayan rock salt are two examples of rock salt.

🎯 Exam Tip: Provide well-known examples of naturally occurring rock salt formations.

Question 11. Uses of sodium bicarbonate
Answer: To prepare breads, cakes and dhokla
In simple words: Sodium bicarbonate is primarily used as a leavening agent in baking to make dough rise and achieve a soft, fluffy texture.

🎯 Exam Tip: Focus on its primary use in baking as a leavening agent and its mild basic nature.

Question 12. Constituents of baking powder.
Answer: Baking soda and mild acid (tartaric acid)
In simple words: Baking powder is a mixture of baking soda (sodium bicarbonate) and a weak acid, typically tartaric acid, which reacts when wet to produce carbon dioxide.

🎯 Exam Tip: Remember both key components: baking soda and a mild acid, often tartaric acid.

Question 13. Substance used to make hard water soft.
Answer: Washing soda i.e. Na2CO3.10H2O.
In simple words: Washing soda, chemically known as sodium carbonate decahydrate, is used to soften hard water by precipitating calcium and magnesium ions.

🎯 Exam Tip: Know the chemical name and formula for washing soda and its role in water softening.

Question 14. Radioactive isotopes used in treatment of bone cancer.
Answer: Strontium - 89, Strontium - 90, Samarium -153, Radium - 223
In simple words: Several radioactive isotopes like Strontium-89, Strontium-90, Samarium-153, and Radium-223 are specifically employed in medical treatments for bone cancer due to their targeted radiation properties.

🎯 Exam Tip: Memorize the specific radioactive isotopes mentioned for bone cancer treatment.

Question 15. Use of Strontium 89 and strontium 90.
Answer: Treatment of bone cancer.
In simple words: Strontium-89 and Strontium-90 are radioactive isotopes used for therapeutic purposes, specifically in the treatment of bone cancer, to target and destroy cancerous cells.

🎯 Exam Tip: Recall that Strontium isotopes (89 and 90) are vital in medical applications, particularly for bone cancer therapy.

Select The Odd Man Out:

Question 1. Sodium sulphate, Barium chloride, Magnesium sulphate, Bleaching powder.
Answer: Bleaching powder, all others are crystalline salt with water of crystallization while bleaching powder is not.
In simple words: Bleaching powder is the odd one out because it's typically an amorphous mixture, unlike the other substances which are crystalline salts, often containing water of crystallization.

🎯 Exam Tip: Understand the physical state and composition difference between bleaching powder and common crystalline salts.

Question 2. Strontium - 89, Strontium - 90, Radium - 223, Iodine -123.
Answer: Iodine -123, it is used to cure hyperthyroidism while others are used to cure bone cancer.
In simple words: Iodine-123 is distinct because it is used to treat hyperthyroidism, whereas Strontium-89, Strontium-90, and Radium-223 are all used in the treatment of bone cancer.

🎯 Exam Tip: Distinguish radioactive isotopes based on their specific medical applications (e.g., hyperthyroidism vs. bone cancer).

Question 3. Soap, Toothpaste, Baking soda, Curd.
Answer: Curd, it is acidic in nature while others are basic in nature.
In simple words: Curd is the odd one out because it is acidic due to lactic acid, while soap, toothpaste, and baking soda are generally basic or alkaline substances.

🎯 Exam Tip: Classify substances based on their pH nature (acidic, basic, neutral).

Question 4. Na2CO3.10H2O, Na2SO4.10H2O, BaCl2.2H2O, CaOCl2
Answer: CaOCl2, it is amorphous in nature while rest are crystalline in nature.
In simple words: CaOCl2 (Bleaching powder) is the odd one out because it is typically an amorphous powder, while the other compounds are crystalline salts containing water of crystallization.

🎯 Exam Tip: Recognize the physical state (crystalline vs. amorphous) of common chemical compounds.

Question 5. Boron-10, Iodine - 131, Cobalt - 60, Iodine - 123.
Answer: Iodine -123, it is used in hyperthyroidism while rest are used in treatment of brain tumour.
In simple words: Iodine-123 is the anomaly here as its primary medical use is for hyperthyroidism treatment, contrasting with Boron-10, Iodine-131, and Cobalt-60, which are typically used for brain tumor treatment or detection.

🎯 Exam Tip: Differentiate radioactive isotopes based on their specific therapeutic targets (e.g., thyroid vs. brain tumors).

Question 6. Na2SO4, K3PO4, MgBr2, HCI.
Answer: HCI, rest all are salts but HCI is an acid.
In simple words: HCl (hydrochloric acid) is the distinct item as it is an acid, whereas Na2SO4, K3PO4, and MgBr2 are all different types of salts.

🎯 Exam Tip: Clearly distinguish between acids and salts based on their chemical classification.

Write The Correlated Terms:

Question. (1) Washing Powder : Basic :: Milk :
Answer: (1) Acidic
In simple words: Just as washing powder is basic, milk is typically acidic due to lactic acid.

🎯 Exam Tip: Understand the pH nature of common household substances.

Question. (2) Na2SO4: Sodium sulphate :: K3PO4 :
Answer: (2) Potassium phosphate
In simple words: This correlation identifies the common name for the given chemical formula; K3PO4 is known as potassium phosphate.

🎯 Exam Tip: Know the chemical names corresponding to common chemical formulas.

Question. (3) CaOCl2: Calcium Oxychloride : : NaHCO3 :
Answer: (3) Sodium hydrogen carbonate
In simple words: This correlation identifies the common name for the given chemical formula; NaHCO3 is known as sodium hydrogen carbonate (baking soda).

🎯 Exam Tip: Be able to identify the chemical names for formulas like CaOCl2 and NaHCO3.

Question. (4) Borax: 10H2O : : Alum :
Answer: (4) 24H2O
In simple words: This correlation points to the number of water molecules of crystallization in the chemical formula; Alum (potash alum) has 24 molecules of water.

🎯 Exam Tip: Remember the fixed number of water molecules in common hydrated salts like borax and alum.

Question. (5) Sodium Sulphate : Na2SO4.10H2O : : Magnesium Sulphate :
Answer: (5) MgSO4.7H2O
In simple words: This correlation provides the chemical formula for the given common name; Magnesium Sulphate is written as MgSO4.7H2O.

🎯 Exam Tip: Be familiar with the chemical formulas for common sulfates and their hydration states.

Question. (6) Bathing soap : High grades fats and oils :: Washing soap :
Answer: (6) Low-grade fats and oils
In simple words: Bathing soap is made from high-grade fats and oils, whereas washing soap typically uses low-grade fats and oils.

🎯 Exam Tip: Understand the differences in raw materials used for bathing soaps versus washing soaps.

Question. (7) Radium - 23 : Bone cancer :: Phosphorus - 32 :
Answer: (7) Polycythemia
In simple words: Radium-223 is used to treat bone cancer, while Phosphorus-32 is used in the treatment of polycythemia, a blood disorder.

🎯 Exam Tip: Match specific radioactive isotopes with their corresponding medical treatments.

Question. (8) Iodine -123 : Hyperthyroidism :: Iodine -131 :
Answer: (8) Tumour detection
In simple words: Iodine-123 is used for hyperthyroidism, and similarly, Iodine-131 is used for tumour detection and treatment in the thyroid.

🎯 Exam Tip: Differentiate between the medical applications of different iodine isotopes.

Question. (9) Clinical deo : 20-25% of aluminium :: Antiperspirant deo : of aluminium chlorohydrate :
Answer: (9) 15%
In simple words: Clinical deodorants contain 20-25% aluminum, while antiperspirant deodorants typically contain about 15% aluminum chlorohydrate.

🎯 Exam Tip: Remember the approximate concentration of aluminum compounds in different types of deodorants.

Question. (10) Sodium carbonate : Na2CO3 : : Sodium bicarbonate :
Answer: (10) NaHCO3
In simple words: Sodium carbonate has the chemical formula Na2CO3, and similarly, sodium bicarbonate has the chemical formula NaHCO3.

🎯 Exam Tip: Know the chemical formulas for both sodium carbonate and sodium bicarbonate.

Question. (11) Curd : Acidic : : Soap :
Answer: (11) Basic
In simple words: If curd is acidic, then soap, generally, is basic.

🎯 Exam Tip: Understand the basic pH properties of common household items.

Question. (12) Calcium Carbonate : CaCO3 : : Magnesium bromide :
Answer: (12) MgBr2
In simple words: If calcium carbonate has the formula CaCO3, then magnesium bromide has the formula MgBr2.

🎯 Exam Tip: Be able to write chemical formulas for common ionic compounds given their names.

Question. (13) Baking Soda : NaHCO3 : : Washing Soda :
Answer: (13) Na2CO3.10H2O
In simple words: Baking soda is NaHCO3, and washing soda is Na2CO3.10H2O.

🎯 Exam Tip: Differentiate and recall the chemical formulas for baking soda and washing soda, including water of crystallization.

Question. (14) Baking Soda : Breads and Cakes: : Washing Soda :
Answer: (14) Hard water soft
In simple words: Baking soda is used in breads and cakes; similarly, washing soda is used to soften hard water.

🎯 Exam Tip: Associate each compound with its primary application.

Question. (15) Borax: Na2B4O7.10H2O : : Alum :
Answer: (15) K2SO4.Al2(SO4)3.24H2O
In simple words: Borax has the formula Na2B4O7.10H2O, and alum (potash alum) has the formula K2SO4.Al2(SO4)3.24H2O.

🎯 Exam Tip: Remember the complete chemical formulas for both borax and alum, including their water of crystallization.

Match The Columns:

Question 1.

Column 'A'	Column 'B'
(1) Barium chloride	(a) 24H2O
(2) Sodium sulphate	(b) 7H2O
(3) Magnesium sulphate	(c) 2H2O
(4) Alum	(d) 10H2O

Answer:(1 - c),
(2 - d),
(3 - b),
(4 - a)
In simple words: This matching exercise pairs various salts with the number of water molecules of crystallization typically associated with their common hydrated forms.

🎯 Exam Tip: Accurately recall the hydration numbers for common salts like barium chloride, sodium sulphate, magnesium sulphate, and alum.

Question 2.

Column 'A'	Column 'B'
(1) Strontium - 90	(a) Brain tumour
(2) Cobalt - 60	(b) Hyperthyroidism
(3) Iodine - 131	(c) Polycythemia
(4) Phosphorus - 32	(d) Bone cancer

Answer:(1 - d),
(2 - a),
(3 - b),
(4 - c)
In simple words: This table matches specific radioactive isotopes from Column 'A' with their respective medical applications or conditions treated, listed in Column 'B'.

🎯 Exam Tip: Familiarize yourself with the medical uses of common radioactive isotopes to correctly match them with their applications.

Give Scientific Reasons:

Question 1. Baking soda is used while making cakes.
Answer:

• Baking soda is chemically known as sodium bicarbonate.
• On heating, sodium bicarbonate decomposes to form sodium carbonate, water and carbon dioxide (CO2).
• The carbon dioxide produced is released due to which the cake becomes soft and spongy.
• Hence, baking soda is used to make cake spongy and soft.

In simple words: Baking soda makes cakes soft and spongy by releasing carbon dioxide gas when heated, which creates air bubbles in the batter.

🎯 Exam Tip: Focus on the chemical decomposition of sodium bicarbonate (NaHCO3) into CO2, H2O, and Na2CO3 upon heating as the key reason.

Question 2. Baking soda is used to reduce acidity in the stomach.
Answer:

• Baking soda is used as a medicine (antacid). When it is taken, it undergoes hydrolysis to give sodium hydroxide in the stomach. Thus, sodium hydroxide neutralizes the hydrochloric acid produced by gastric juice and gives relief to the patient from acidity.


• \( \text{NaHCO}_3 + \text{H}_2\text{O} \)
  \( \implies \text{NaOH} + \text{H}_2\text{O} + \text{CO}_2\uparrow \)


• \( \text{Baking water} + \text{Soda} \implies \text{Sodium hydroxide} + \text{Water} + \text{CO}_2\uparrow \)


• \( \text{NaOH} + \text{HCl} \implies \text{NaCl} + \text{H}_2\text{O} \)


• \( \text{Sodium hydroxide} + \text{Hydrochloric acid} \implies \text{Sodium chloride} + \text{water} \)

In simple words: Baking soda acts as an antacid by reacting with stomach acid, hydrochloric acid, to neutralize it, thus providing relief from acidity.

🎯 Exam Tip: Understand that baking soda (sodium bicarbonate) is a mild base that reacts with acidic stomach contents to neutralize them, highlighting its role as an antacid.

Question 3. Tap water and water in swimming pool has a typical strong odour in the rainy season.
Answer:

• Tap water and water in swimming pool has a typical strong odour in the rainy season, it is the odour of the chlorine gas that is used to destroy the microbes in the water.
• Chlorine gas is a strong oxidizing agent and therefore, it has a strong disinfecting as well as bleaching action.
• Chlorine is inconvenient to handle because of its gaseous state. Instead, the solid bleaching powder which has the same effect is more convenient to use.
• Bleaching powder undergoes slow decomposition due to the carbon dioxide in air and chlorine gas is released. Bleaching powder gets its property because of this release of chlorine gas.


• \( \text{CaOCl}_2 + \text{CO}_2 \)
  \( \implies \text{CaCO}_3 + \text{CL}_2\uparrow \)


• \( \text{Bleaching powder} + \text{Carbon dioxide (from air)} \implies \text{Calcium carbonate} + \text{Chlorine} \)

In simple words: The strong odor in tap water and swimming pools, especially in the rainy season, is due to the chlorine gas released from disinfectants like bleaching powder, which kills microbes.

🎯 Exam Tip: Explain the odor as a result of chlorine gas, which is a disinfectant, and mention the decomposition of bleaching powder to release chlorine.

Question 4. Sodium carbonate is added to hard water to make it soft.
Answer:

• The hardness of water is due to the presence of chlorides and sulphates of calcium and magnesium in it.
• Na2CO3 is added to it to soften such water and make it suitable for use.
• The reaction with Na2CO3 causes the formation of insoluble carbonate salts of magnesium and calcium thus making the water soft.

In simple words: Sodium carbonate softens hard water by reacting with the calcium and magnesium salts present, forming insoluble carbonates that precipitate out, removing the hardness.

🎯 Exam Tip: Emphasize that sodium carbonate (Na2CO3) precipitates out the calcium and magnesium ions responsible for water hardness.

Question 5. Alum is used in the process of water purification.
Answer:

• Alum is used in the process of water purification because of property of coagulation.
• The solid impurities in water come together, become heavy and settle to the bottom.
• As a result, the water above becomes clear.

In simple words: Alum purifies water through coagulation, where it clumps tiny impurities together, making them heavy enough to settle down and clarifying the water.

🎯 Exam Tip: Highlight the coagulation property of alum, which causes suspended impurities to aggregate and settle, making water clear.

Question 6. Overconsumption of artificial food colours should be avoided?
Answer:

• The overconsumption of artificial food colours should be avoided because they can be detrimental to health.
• Food colours added to pickles, jam and sauce contain small quantities of lead and mercury. These can be harmful for those who consume these products on a regular basis.
• Diseases like ADHD (Attention Deficit Hyperactivity Disorder) can affect children due to excessive consumption of foods with added food colours.

In simple words: Overconsuming artificial food colors is risky because they may contain harmful heavy metals like lead and mercury, potentially leading to health issues such as ADHD in children.

🎯 Exam Tip: Mention the presence of heavy metals (lead, mercury) and potential health impacts like ADHD in children as key reasons for avoidance.

Question 7. Artificial colours in Rang Panchami should be used cautiously.
Answer:

• We regularly use artificial colours on Rang Panchami.
• The red colour used on Rang Panchami is very dangerous. It contains a high proportion of mercury in it.
• This poses risks like blindness, skin cancer, asthma, itching of the skin, permanent blocking of sweat pores etc.
• Therefore, it is necessary that artificial colours are used cautiously.

In simple words: Artificial colors, especially red ones containing mercury, used during Rang Panchami can cause severe health issues like blindness, skin cancer, and asthma, necessitating cautious use.

🎯 Exam Tip: Emphasize the danger of mercury in artificial colors, especially red, and its potential to cause various health problems, necessitating caution.

Question 8. There are various brands of bleaching powder in the market.
Answer:

• When bleaching powder comes in contact with air, it reacts with carbon dioxide to form calcium carbonate and releases chlorine gas. CaOCl2 + CO2 → CaCO3 + Cl2 ↑ (from air)
• This generated chlorine is known as "available chlorine."
• On the basis of the percentage of "available chlorine” various brands of bleaching powder are available in the market.

In simple words: Different brands of bleaching powder exist because their effectiveness, measured by the percentage of "available chlorine" released upon reaction with carbon dioxide, varies and is a key distinguishing factor.

🎯 Exam Tip: Connect the availability of various brands to the concept of "available chlorine," which indicates the bleaching powder's strength and effectiveness.

Question 9. We use anodized cooking utensils like griddles and cookers.
Answer:

• Anodizing is process of forming a protective rayer of hydrated aluminium oxide on utensils.
• Due to anodizing, the surface of the cooking utensils become non-standing, non-toxic and non-reactive with the ingredients of the foot.
• These utensils get heated faster and withstand high heat.
• Also the amount of butter, ghee or oil used to cook food in these type of utensils is neglible.
• These utensils are tough, durable and resistant to corrosion.
• Hence, we use anodized cooking utensils like gridders and cookers.

In simple words: Anodized cooking utensils are preferred because the protective aluminum oxide layer makes them non-stick, non-toxic, highly durable, corrosion-resistant, and efficient in heat distribution, reducing the need for excess oil.

🎯 Exam Tip: Focus on the advantages of anodization, such as non-stick properties, durability, corrosion resistance, and heat efficiency, as reasons for its use in cookware.

Explain The Following Chemical Reactions With The Help Of Balanced Equations :

Question 1. Sodium hydroxide reacts with dilute Hydrochloric acid.
Answer: When Sodium hydroxide reacts with dilute Hydrochloric acid, it forms sodium chloride and water.
This is a neutralization reaction.
\( \text{NaOH} + \text{HCl} \implies \text{NaCl} + \text{H}_2\text{O} \)
\( \text{Sodium hydroxide} + \text{Hydrochloric acid} \implies \text{Sodium chloride (salt)} + \text{water} \)
In simple words: Sodium hydroxide, a base, reacts with hydrochloric acid to form sodium chloride (salt) and water in a classic neutralization reaction.

🎯 Exam Tip: Remember the products of an acid-base neutralization reaction: a salt and water, and ensure the equation is balanced.

Question 2. When an electric current is passed through a saturated solution of sodium chloride (brine)
Answer: When an electric current is passed through a saturated solution of sodium chloride (brine) it is electrolysed and hydrogen gas is released at the cathode while chlorine gas is released at the anode. Also, an important basic compound NaOH is formed in the cell.
\( \text{2NaCl} + \text{2H}_2\text{O} \xrightarrow{\text{electric current}} \text{2NaOH} + \text{Cl}_2\uparrow + \text{H}_2\uparrow \)
\( \text{Sodium chloride (brine)} + \text{water} \xrightarrow{\text{electric current}} \text{Sodium hydroxide} + \text{Chlorine} + \text{Hydrogen} \)
In simple words: Passing electric current through brine (saturated sodium chloride solution) produces hydrogen gas at the cathode, chlorine gas at the anode, and sodium hydroxide in the solution.

🎯 Exam Tip: Understand the electrolysis of brine, identifying the products (NaOH, Cl2, H2) and their respective locations (solution, anode, cathode).

Question 3. Baking soda (Sodium hydrogen carbonate) reacts with dilute hydrochloric acid.
Answer: When Sodium bicarbonate (Sodium hydrogen carbonate) reacts with dilute hydrochloric acid, it gives sodium chloride, water and carbon dioxide gas is liberated.
\( \text{NaHCO}_{3(s)} + \text{HCl}_{(aq)} \implies \text{NaCl}_{(aq)} + \text{H}_2\text{O}_{(l)} + \text{CO}_{2(g)}\uparrow \)
\( \text{Sodium bicarbonate} + \text{Hydrochloric acid} \implies \text{Sodium chloride} + \text{Water} + \text{Carbon dioxide} \)
In simple words: Baking soda reacts with dilute hydrochloric acid to produce salt (sodium chloride), water, and carbon dioxide gas, which causes fizzing.

🎯 Exam Tip: Remember that the reaction of a carbonate/bicarbonate with an acid produces carbon dioxide gas, a salt, and water.

Question 4. Bleaching powder is exposed to air.
Answer: When bleaching powder is exposed to air, it undergoes slow decomposition due to the carbon dioxide in air and chlorine gas is released.
\( \text{CaOCl}_2 + \text{CO}_2 \)
\( \implies \text{CaCO}_3 + \text{CL}_2\uparrow \)
\( \text{Bleaching powder} + \text{Carbon dioxide (from air)} \implies \text{Calcium carbonate} + \text{Chlorine} \)
In simple words: When exposed to air, bleaching powder slowly decomposes by reacting with atmospheric carbon dioxide, releasing chlorine gas and calcium carbonate.

🎯 Exam Tip: Note that this decomposition releases chlorine gas, which is responsible for the characteristic smell and bleaching action of bleaching powder.

Question 5. When dry slaked lime reacts with chlorine gas.
Answer: When dry slaked lime reacts with chlorine gas, it gives bleaching powder.
\( \text{Ca(OH)}_2 + \text{Cl}_2 \implies \text{CaOCl}_2 + \text{H}_2\text{O} \)
\( \text{Slaked lime} + \text{Chlorine} \implies \text{Bleaching powder} + \text{Water} \)
In simple words: Dry slaked lime reacts with chlorine gas to form bleaching powder and water.

🎯 Exam Tip: This is the manufacturing reaction for bleaching powder; remember the reactants (slaked lime and chlorine) and products (bleaching powder and water).

Question 6. Bleaching powder reacts with dilute sulphuric acid.
Answer: Dilute sulphuric acid reacts rapidly with bleaching powder to form calcium sulphate and release chlorine gas completely.
\( \text{CaOCl}_2 + \text{H}_2\text{SO}_4 \)
\( \implies \text{CaSO}_4 + \text{Cl}_2\uparrow + \text{H}_2\text{O} \)
\( \text{Bleaching powder} + \text{Dilute sulphuric acid} \implies \text{Calcium sulphate} + \text{Chlorine} + \text{Water} \)
In simple words: Bleaching powder reacts with dilute sulphuric acid to produce calcium sulphate, water, and chlorine gas.

🎯 Exam Tip: Understand that acids react with bleaching powder to liberate chlorine gas, which is the active bleaching agent.

Question 7. Bleaching powder reacts with dilute hydrochloric acid.
Answer: Dilute hydrochloric acid reacts rapidly with bleaching powder to form Calcium chloride and release chlorine gas completely.
\( \text{CaOCl}_2 + \text{2HCl} \)
\( \implies \text{CaCl}_2 + \text{Cl}_2\uparrow + \text{H}_2\text{O} \)
\( \text{Bleaching powder} + \text{Dilute hydrochloric acid} \implies \text{Calcium chloride} + \text{Chlorine} + \text{Water} \)
In simple words: Bleaching powder reacts vigorously with dilute hydrochloric acid, forming calcium chloride, water, and releasing chlorine gas.

🎯 Exam Tip: Similar to sulphuric acid, hydrochloric acid also reacts with bleaching powder to release chlorine gas. Remember the balanced equation.

Question 8. Sodium carbonate reacts with magnesium chloride.
Answer: When Sodium carbonate reacts with magnesium chloride, it forms insoluble magnesium carbonate and sodium chloride. This reaction is used to make hard water soft.
\( \text{MgCl}_{2(aq)} + \text{Na}_2\text{CO}_{3(s)} \)
\( \implies \text{MgCO}_{3(s)} + \text{2NaCl}_{(s)} \)
\( \text{Magnesium chloride} + \text{Sodium carbonate} \implies \text{Magnesium carbonate} + \text{Sodium chloride} \)
In simple words: Sodium carbonate reacts with magnesium chloride to form insoluble magnesium carbonate and sodium chloride, a process used to soften hard water.

🎯 Exam Tip: This precipitation reaction is crucial for water softening; understand that insoluble magnesium carbonate removes magnesium ions from water.

Question 9. Crystalline sodium carbonate is exposed to air.
Answer: When crystalline sodium carbonate is exposed to air it loses its water of crystallization readily and a white powder is obtained. This powder is called washing soda.
\( \text{Na}_2\text{CO}_3\text{.10H}_2\text{O} \implies \text{Na}_2\text{CO}_3\text{.H}_2\text{O} \)
\( \text{Crystalline Sodium carbonate} \implies \text{White powder (Washing soda)} \)
In simple words: Crystalline sodium carbonate (washing soda) loses its water of crystallization when exposed to air, turning into a white powder, a process called efflorescence.

🎯 Exam Tip: Remember the term "efflorescence" for the process where hydrated salts lose their water of crystallization upon exposure to air.

Question 10. Sodium carbonate reacts with sulphuric acid.
Answer: When sodium carbonate reacts with sulphuric acid it forms sodium sulphate, water and carbon dioxide gas is liberated.
\( \text{Na}_2\text{CO}_3 + \text{H}_2\text{SO}_4 \)
\( \implies \text{Na}_2\text{SO}_4 + \text{H}_2\text{O} + \text{CO}_2\uparrow \)
\( \text{Sodium carbonate} + \text{Sulphuric acid} \implies \text{Sodium sulphate} + \text{Water} + \text{Carbon dioxide} \)
In simple words: Sodium carbonate reacts with sulphuric acid to produce sodium sulphate, water, and carbon dioxide gas.

🎯 Exam Tip: Like other carbonates, sodium carbonate reacts with acids to produce carbon dioxide gas, along with a salt and water.

Distinguish Between:

Question 1. Washing soda and Baking soda
Answer:

Washing soda	Baking soda
(i) Chemical name is sodium carbonate.	(i) Chemical name is sodium bicarbonate or sodium hydrogen carbonate.
(ii) Its molecular formula is Na2CO3.10H2O	(ii) Its molecular formula is NaHCO3
(iii) It is a crystalline substance.	(iii) It is an amorphous powder.
(iv) It is used in manufacturing soaps and detergents.	(iv) It is used in bakery for making cakes and bread lighter and spongy.

In simple words: Washing soda is sodium carbonate decahydrate, a crystalline substance used in cleaning, while baking soda is sodium bicarbonate, an amorphous powder primarily used as a leavening agent in baking.

🎯 Exam Tip: Focus on their chemical names, formulas, physical state, and primary uses for clear differentiation.

Question 2. Bathing soap and Washing soap
Answer:

Bathing soap	Washing soap
(i) High-grade fats and oils are used as the raw material.	(i) Low-grade fats and oils are used as the raw material.
(ii) Expensive perfumes added.	(ii) Cheaper perfumes added.
(iii) No free alkali content present to prevent injuries to skin.	(iii) Free alkali present for cleaning action.

In simple words: Bathing soaps use high-grade fats, expensive perfumes, and contain no free alkali to be gentle on skin, whereas washing soaps use lower-grade fats, cheaper perfumes, and have free alkali for strong cleaning.

🎯 Exam Tip: Differentiate them based on the quality of raw materials, perfume cost, and the presence/absence of free alkali, which affects skin safety and cleaning power.

Answer The Following:

Question 1. Give the properties and uses of Sodium bicarbonate.
Answer: Properties and uses of sodium bicarbonate

• (i) NaHCO2 reacts with moist litmus paper and red litmus turns blue which means that it is basic in nature.
• (ii) It is used to make bread, cake, dhokla.
• (iii) Being basic in nature it is used to reduce acidity in the stomach.
• (iv) NaHCO3 is used to make the active substance CO2 in the fire extinguisher.
• (v) Baking soda is used to clean an oven.

In simple words: Sodium bicarbonate (baking soda) is a basic compound used as a leavening agent in baking, an antacid for stomach acidity, a source of CO2 in fire extinguishers, and for cleaning ovens.

🎯 Exam Tip: Highlight its basic nature, uses in baking (CO2 release), antacid properties, and role in fire extinguishers.

Question 2. Give the properties and uses of washing soda.
Answer: Properties and uses of washing soda :

• Washing soda is a whitish and odourless powder at room temperature.
• Litmus has a blue colour in its aqueous solution.
• It is hygroscopic, that is, it absorbs moisture if left exposed to air.
• It is used mainly for washing clothes.
• Sodium carbonate is used in the glass and paper industry and also in refining of petrol.

In simple words: Washing soda is a whitish, hygroscopic, basic powder primarily used for washing clothes, in glass and paper manufacturing, and for refining petrol.

🎯 Exam Tip: Emphasize its physical properties (whitish, odorless, hygroscopic), basic nature, and main applications in laundry and industrial processes.

Question 3. Name some substances in our daily use which contain water of crystallization.
Answer:

• Alum (Potash alum - K2SO4.Al2(SO4)3.24H2O)
• Borax (Na2B4O7.10H2O)
• Epsom salt (Magnesium sulphate MgSO4.7H2O)
• Barium chloride (BaCl2.2H2O)
• Sodium sulphate (Glauber's salt Na2SO4.10H2O)

In simple words: Common substances with water of crystallization include alum, borax, Epsom salt, barium chloride, and Glauber's salt.

🎯 Exam Tip: Be ready to list several examples of hydrated salts, remembering their common names and corresponding chemical formulas including water molecules.

Question 4. Give the uses of radioactive isotopes in the measurement of thickness, density and level.
Answer: Measurement of thickness, density and level:

• It is necessary to maintain the required thickness in the manufacture of aluminium, plastic, iron sheets of differing thickness.
• In the manufacturing process, a radioactive substance is placed on one side and an instrument to measure radiation on the other.
• The radiation read by the measuring instrument varies with the thickness of the sheet.
• Material inside a packing can also be examined by the same technique.

In simple words: Radioactive isotopes are used in industry to precisely measure the thickness of materials like aluminum or plastic sheets, determine material density, and monitor liquid levels by detecting changes in radiation passing through the substance.

🎯 Exam Tip: Explain the principle: radiation absorption varies with material thickness/density, allowing precise measurement in manufacturing without physical contact.

Question 5. Give the uses of radioactive isotopes in Luminescent paint and radioluminescence.
Answer: Luminescent paint and radioluminescence:

• The radioactive substances radium, promethium, tritium with some phosphour are used to make certain objects visible in the dark, for example, the hands of a clock, and certain other objects.
• Krypton-85 is used in HID (High-Intensity Discharge) lamps while promethium-147 is used in portable X-ray units as the source of beta rays.

In simple words: Radioactive isotopes like radium, promethium, and tritium are combined with phosphors to create luminescent paints for glow-in-the-dark objects, while Krypton-85 and promethium-147 find use in specialized lighting and portable X-ray units, respectively.

🎯 Exam Tip: Focus on two main applications: glow-in-the-dark paints using phosphors and radioactive isotopes, and specialized light sources/X-ray units.

Question 6. Give the uses of radioactive isotopes in Field of agriculture.
Answer: Field of agriculture:

• The genes and chromosomes that give seeds properties like fast growth, higher productivity, etc. can be modified by means of radiation.
• The radioactive isotope cobalt-60 is used for food preservation.
• Onions, potatoes are irradiated with gamma rays from cobalt-60 to prevent their sprouting.
• Strontium-90 is used as a tracer in the research on various crops.

In simple words: In agriculture, radioactive isotopes help modify seed properties for better yields, preserve food like onions and potatoes by preventing sprouting (using Cobalt-60), and serve as tracers in crop research (e.g., Strontium-90).

🎯 Exam Tip: Remember the applications such as genetic modification of seeds, food preservation (Cobalt-60 for anti-sprouting), and nutrient tracing in crops (Strontium-90).

Question 7. Give the uses of dyes.
Answer: Uses of dyes :

• They are used for colouring cloth and hair.
• Fluorescent colours are used to make street boards that are visible at night.
• Dyes are used to polish leather shoes, purses and chappals.

In simple words: Dyes are primarily used for coloring textiles and hair, creating reflective fluorescent street signs, and polishing leather goods.

🎯 Exam Tip: List practical applications across various sectors, focusing on their primary function of imparting color or visibility.

Question 8. What are the adverse effects of dyes?
Answer: Adverse effects dyes :

• Dyeing hair can have adverse effects like hair fall, damage to hair texture, burning of skin, adverse effect on eyes, etc.
• Lipstick contains a dye named carmine. It does not affect lips but causes stomach disorders.
• Excessive use of plants for making natural dyes results in deterioration of the environment.

In simple words: Dyes can cause hair damage, skin irritation, eye problems, and stomach disorders (from lipstick dyes), while over-harvesting plants for natural dyes harms the environment.

🎯 Exam Tip: Categorize adverse effects by application (hair, cosmetics) and environmental impact (resource depletion).

Question 9. Give the uses of teflon.
Answer: Uses of teflon :

• Teflon is a poor conductor of electricity. Therefore, Teflon clad wires and parts are used in high technology electronic instruments.
• It is used for making non-stick kitchenware.
• The coloured metal sheets of two-wheelers and four-wheelers are given a Teflon coating to protect them from damage due to high temperature and rain.

In simple words: Teflon is used in electronics due to its electrical insulation, in non-stick cookware because of its low friction, and as a protective coating on vehicles against environmental damage.

🎯 Exam Tip: Focus on its key properties: electrical insulation, non-stick surface, and protective coating capabilities in various applications.

Question 10. What is ceramic? Give examples.
Answer:

• Ceramic is a heat resistant substance formed by kneading an inorganic substance in water and then shaping it and hardening it by heating.
• Pots made by a potter, Mangalore roofing tiles, construction bricks, pottery, terracotta articles are some examples of common ceramic articles that we see around.

In simple words: Ceramic is a heat-resistant material created by shaping and heating inorganic substances mixed with water; common examples include pottery, roofing tiles, bricks, and terracotta items.

🎯 Exam Tip: Define ceramic as a heat-resistant, inorganic material formed by heating, and provide diverse examples like pottery, bricks, and tiles.

Question 11. Give the uses of ceramics.
Answer:

• Ceramics can withstand high temperatures without decomposing. Ceramic is brittle, water-resistant and an electrical insulator.
• Therefore, it is used in electrical instruments, for coating the interior of a kiln, the outer surfaces of ships and blades of jet engines.
• A certain type of ceramic tiles are fixed on the outer layer of a space shuttle.
• Some types of ceramics are used as superconductors.

In simple words: Ceramics are used in electrical instruments due to their insulating and heat-resistant properties, for coating kilns and jet engines, as tiles on space shuttles, and in specialized applications as superconductors.

🎯 Exam Tip: Highlight properties like high temperature resistance, electrical insulation, and applications in extreme environments (kilns, jet engines, space shuttles) and advanced technology (superconductors).

Question 12. What is brine? What happens when ^th of this solution is evaporated?
Answer:

• The 25% aqueous solution of salt is called saturated brine.
• When th of this solution is evaporated the dissolved salt gets crystallized and salt gets separated from the solution.

In simple words: Brine is a 25% saturated salt solution; evaporating a portion of it causes the dissolved salt to crystallize and separate from the remaining solution.

🎯 Exam Tip: Define brine by its salt concentration and explain that evaporation leads to salt crystallization, which is a common method for salt recovery.

Question 13. What is baking soda? Give its chemical name and molecular formula.
Answer:

• Baking soda is a white non-crystalline powder.
• Its chemical name is sodium hydrogen carbonate or sodium bicarbonate and its molecular formula is NaHCO3.

In simple words: Baking soda is a white, non-crystalline powder chemically known as sodium hydrogen carbonate or sodium bicarbonate, with the molecular formula NaHCO3.

🎯 Exam Tip: Remember its physical appearance, both chemical names (sodium hydrogen carbonate/bicarbonate), and its molecular formula (NaHCO3).

Question 14. Give two uses of Blue vitriol.
Answer:

• Blue vitriol is used in the blood test for diagnosing anaemia.
• Bordeaux mixture which is a mixture of slaked lime and blue vitriol is used as a fungicide on fruits like grapes and musk melon.

In simple words: Blue vitriol is used in blood tests to diagnose anemia and, combined with slaked lime, forms Bordeaux mixture, a fungicide for fruits.

🎯 Exam Tip: Recall its use in medical diagnostics (anemia) and as a component of the Bordeaux mixture fungicide in agriculture.

Question 15. What is radioactivity and what are radioactive substances?
Answer:

• Elements with a high atomic number such as uranium, thorium, radium have a property of spontaneously emitting invisible, highly penetrating and high energy radiation. This property is called radioactivity.
• A substance having this property is called a radioactive substance.

In simple words: Radioactivity is the spontaneous emission of invisible, high-energy radiation by elements with high atomic numbers, and substances exhibiting this property are called radioactive substances.

🎯 Exam Tip: Define radioactivity as a spontaneous emission of high-energy radiation by certain heavy elements, and radioactive substances as those possessing this property.

Question 16. What can you say about the uses of radioactive isotopes?
Answer:

• It is a misconception that radioactive elements are used only for making an atom bomb.
• Radioactive isotopes are used in various fields such as scientific research, agriculture, industry, medicine, etc.
• Radioactive substances are used in two ways.
• By using the radiation alone.
• By using the radioactive element itself.

In simple words: Radioactive isotopes have wide-ranging applications beyond atomic bombs, including scientific research, agriculture (like food preservation and tracing), industrial uses (such as radiography and thickness measurement), and medical treatments and diagnostics. They can be used directly for their radiation or as part of a radioactive substance.

🎯 Exam Tip: When discussing the uses of radioactive isotopes, categorize them by field (e.g., medical, industrial, agricultural) to demonstrate a comprehensive understanding of their applications.

Question 17. Give the uses of radioactive isotopes in Radiography.
Answer:

• Internal cracks and voids in cast iron articles and iron solder can be detected with the help of gamma rays.
• For this purpose, isotopes like cobalt-60, iridium-192 are used in the radiography camera.
• This technique is used for detecting flaws in metalwork.

In simple words: Radioactive isotopes like cobalt-60 and iridium-192 are used in industrial radiography to detect hidden flaws such as cracks or voids in metal objects, ensuring the quality and safety of manufactured parts.

🎯 Exam Tip: Remember specific isotopes (cobalt-60, iridium-192) used in industrial radiography for better scores. Mentioning the type of radiation (gamma rays) and the application (detecting flaws in metalwork) is crucial.

Question 18. Give the uses of radioactive isotopes in ceramic articles.
Answer:

• Luminous colours are used to decorate ceramic tiles, utensils, plates, etc.
• Earlier uranium oxide was used in these paints.

In simple words: Radioactive isotopes are used to create luminous colors for decorating ceramic items like tiles and utensils, with uranium oxide being an earlier substance used for this purpose.

🎯 Exam Tip: Note that "luminous colours" and "uranium oxide" are the key terms for this application. Emphasize their role in ceramic decoration.

Question 19. What is a dye?
Answer:The coloured substance which on applying to an article, imparts that colour to the article, is called a dyeIn simple words: A dye is a colored substance that, when applied to an article, imparts its color to that article.

🎯 Exam Tip: A concise and accurate definition is essential. Focus on "coloured substance" and "imparts colour."

Question 20. What is done to fix a dye on the cloth?
Answer:

• A mordant is to be used to fix the colour after dyeing a cloth.
• A mordant is a chemical binding agent that adheres well to both the fibers and the dye.

In simple words: To permanently fix a dye on cloth, a mordant is used; it's a chemical that helps the dye bind effectively to the fabric fibers.

🎯 Exam Tip: The term "mordant" and its function as a "chemical binding agent" are the main points. Explain how it facilitates adherence between the dye and fabric.

Question 21. What is Teflon? Give its chemical name.
Answer:

• Teflon is the polymer of tetrafluoroethylene.
• Its chemical name is polytetrafluoroethylene (C2F4)n

In simple words: Teflon is a polymer derived from tetrafluoroethylene, and its full chemical name is polytetrafluoroethylene.

🎯 Exam Tip: Accurately stating both the common name (Teflon) and its chemical identity (polytetrafluoroethylene with formula \((C_2F_4)_n\)) is vital for this question.

Question 22. What is powder coating? Why is it done?
Answer:

• Powder coating is a method of applying a layer harder than paint on the surface of plastic, medium density fibre (MDF).
• Board and iron object to make them attractive, durable and to prevent rustihg respectively.

In simple words: Powder coating is a technique that applies a durable, hard layer, superior to paint, onto surfaces like plastic, MDF boards, and iron objects to enhance their attractiveness, durability, and prevent rusting.

🎯 Exam Tip: Define powder coating as a superior alternative to paint. Mention its benefits (attractive, durable, rust prevention) and the types of materials it is applied to.

Question 23. Give the properties of ceramics.
Answer:

• Ceramics can withstand high temperatures without decomposing.
• Ceramic is brittle, water resistant and an electrical insulator.

In simple words: Ceramics are materials known for their ability to withstand high temperatures without breaking down, and they are typically brittle, water-resistant, and good electrical insulators.

🎯 Exam Tip: List at least three distinct properties: heat resistance, brittleness, water resistance, and electrical insulation. Accuracy in each property is key.

Question 24. How is bone china made? How is it different from porcelain?
Answer:

• Bone china is made by adding some ash of animal bones in the mixture of china clay, feldspar and fine silica while making porcelain.
• This ceramic is harder than porcelain.

In simple words: Bone china is created by incorporating animal bone ash into a mix of china clay, feldspar, and silica, which results in a ceramic material that is notably harder than traditional porcelain.

🎯 Exam Tip: Highlight the unique ingredient (animal bone ash) and the key difference (hardness) compared to porcelain. Mentioning the other components of the mix is also beneficial.

Question 25. What compounds are used instead of clay for making advanced ceramic?
Answer:Oxides like Alumina (Al2O3), Zirconia (ZrO2) Silica (SiO2) and some other compounds like silicon carbide (SiC), boron carbide (B4C) are used instead of clay for making advanced ceramic.In simple words: For advanced ceramics, compounds such as alumina, zirconia, silica, silicon carbide, and boron carbide are used as primary materials instead of traditional clay.

🎯 Exam Tip: Name specific compounds (Al2O3, ZrO2, SiO2, SiC, B4C) to demonstrate knowledge of advanced ceramic materials. The chemical formulas are important.

Question 26. What is sintering?
Answer:

• Advanced ceramics requires a temperature of 1600 to 1800 °C and an oxygen-free atmosphere for firing.
• This process is called sintering.

In simple words: Sintering is a high-temperature firing process, typically between 1600-1800°C in an oxygen-free environment, used to solidify and densify advanced ceramic materials.

🎯 Exam Tip: Define sintering by emphasizing the high temperature, oxygen-free atmosphere, and its purpose in the creation of advanced ceramics.

Write Short Notes On:

Question 1. Chernobyl disaster.
Answer:

• On 26th April 1986, the graphite reactor in the Chernobyl atomic power plant exploded, and suddenly the radioactive isotopes and radiation came out.
• Due to this episode, radioactive isotopes entered the human body through water and land and caused genetic disorders.
• These got carried further into the next generation.
• Thyroid disorders increased in children as well as adults.
• As a result, the incidence of throat diseases is greater there than in other places.

In simple words: The Chernobyl disaster, a nuclear reactor explosion in 1986, released vast amounts of radioactive material, leading to widespread contamination, genetic disorders, and increased cases of thyroid and throat diseases across generations due to environmental absorption.

🎯 Exam Tip: Include the date (April 26, 1986), the cause (graphite reactor explosion), the consequences (radioactive release, genetic disorders, thyroid/throat diseases), and the environmental pathways (water and land).

Question 2. Food colours.
Answer:

• Food colours are mixed in most soft drinks and foodstuffs available in the market.
• These food colours are in the form of powders, gels and pastes.
• Food colours are used in domestic as well as commercial products.
• Certain colours and essences are added to ice cream, ice candies, sauce, fruit juices, cold drinks, pickles, jams and jellies.
• Food colours are often found to be added to packaged meat (chicken, mutton), chilli powder, turmeric, sweets and other similar substances so as to give them a good colour.
• Food colours are natural as well as artificial.
• The food colours prepared from seeds, beetroot, flowers and fruit concentrate are natural.
• Tetrazene, sunset yellow are artificial food colours used extensively.
• However, over-consumption of artificial food colours can be detrimental to health. Therefore, usage of natural food colours is always good.

In simple words: Food colours, available as powders, gels, or pastes, are used in many food products, both natural (from plants) and artificial (like tetrazene, sunset yellow), to enhance their appearance, but excessive consumption of artificial types can be harmful, making natural alternatives preferable.

🎯 Exam Tip: Differentiate between natural and artificial food colours, give examples of common artificial colours (tetrazene, sunset yellow), mention various products where they are used, and highlight the health risks of overconsumption.

Question 3. Anodizing.
Answer:

• A protective layer is formed naturally on the surface of aluminium metal by reaction with oxygen in air.
• In the anodizing process, this layer can be made of the desired thickness.
• Anodizing is done by electrolysis.
• Dilute sulphuric acid is taken in the electrolytic cell and the aluminium article is dipped in it as the anode.
• When an electric current is passed, hydrogen gas is released at the cathode and oxygen gas at the anode.
• A reaction with oxygen occurs and a layer of hydrated aluminium oxide is formed on the anode, i.e. the aluminium article.
• This layer can be made attractive by adding colour in the cell during electrolysis.

In simple words: Anodizing is an electrolytic process that enhances the natural protective oxide layer on aluminum by making it a desired thickness, forming hydrated aluminum oxide on the anode, and can even incorporate colors for aesthetic appeal.

🎯 Exam Tip: Explain anodizing as an electrolytic process that thickens the natural oxide layer on aluminum. Mention the role of dilute sulphuric acid, the aluminum article as the anode, and the possibility of adding color for attractiveness.

Answer The Following Questions:

Question 1. What are salts? Give their source.
Answer:

• The ionic compounds which do not contain H+ and OH ions and contain only one kind of cation and anion are called simple salts.
• For example, Na2SO4, K3PO4, CaCl2.
• The sea is said to be a rich source of salts of various elements such as chlorine, sodium, magnesium, potassium, calcium, bromine.
• The important salts found in sea water are:

(a) Sodium chloride
(b) Magnesium chloride
(c) Magnesium sulphate
(d) Potassium chloride
(e) Calcium carbonate
(f) Magnesium bromide

In simple words: Salts are ionic compounds lacking H+ and OH- ions, typically composed of one cation and one anion, and a major natural source for various salts like sodium chloride, magnesium chloride, and calcium carbonate is seawater.

🎯 Exam Tip: Provide a clear definition of simple salts (ionic compounds without H+ or OH-, having one cation and one anion). Crucially, identify the primary source (sea) and list at least 3-4 specific examples of salts found there.

Question 2. Which are the three kinds of salts depending on their pH value? How are they formed?
Answer:The three kinds of salts depending on their pH value are:

Neutral salts:
Salt is neutral when its pH value is 7. Such a salt is made from a strong acid and a strong base.

Acidic salts:
The pH value of a salt made from a strong acid and a weak base is less than 7 and it is acidic.

Basic salts:
The pH value of a salt made from a weak acid and strong base is more than 7 and it is basic.In simple words: Salts are categorized into neutral (pH 7, from strong acid + strong base), acidic (pH < 7, from strong acid + weak base), and basic (pH > 7, from weak acid + strong base), based on their pH value and the strength of the acid and base from which they are formed.

🎯 Exam Tip: Clearly define each type of salt (neutral, acidic, basic) by its pH range and the combination of strong/weak acid and base that forms it. This shows a deep understanding of salt properties.

Question 3. Which is the most used salt? What is its chemical name? How is it formed?
Answer:

• Table salt, or common salt, which gives a salty taste to food, is the most used of all salts.
• Its chemical name is Sodium chloride.
• Sodium chloride is formed by a neutralization reaction between sodium hydroxide and hydrochloric acid.
• Chemical reaction
• This is a neutral salt and the pH value of its aqueous solution is 7.

In simple words: The most widely used salt is common table salt, chemically known as sodium chloride, which forms when sodium hydroxide neutralizes hydrochloric acid, resulting in a neutral solution with a pH of 7.

🎯 Exam Tip: Identify common salt, state its chemical name (sodium chloride), and explain its formation through a neutralization reaction between a strong acid (HCl) and a strong base (NaOH). Mentioning its neutral pH is a bonus.

Question 4. How is bleaching powder obtained?
Answer:

• Bleaching powder is obtained by the reaction of chlorine gas with slaked lime.
• Chemical reaction

In simple words: Bleaching powder is produced by reacting chlorine gas with slaked lime.

🎯 Exam Tip: Clearly state the two reactants: chlorine gas and slaked lime. A concise answer is sufficient here.

Question 5. How is hard water from well converted to soft water?
Answer:

• The hard water from a well or a bore-well becomes soft on adding washing soda and we come to know this from the lather formed on it.
• The hardness of water is due to the presence of chlorides and sulphates of calcium and magnesium in it.
• Na2CO3 is added to it to soften such water and make it suitable for use.
• The reaction with Na2CO3 causes the formation of insoluble carbonate salts of magnesium and calcium.
• Chemical reaction
  MgCl2(aq) + Na2CO3(s) \(\implies\) MgCO3(s) + 2NaCl(s)
  Magnesium chloride + Sodium carbonate \(\implies\) Magnesium carbonate + Sodium chloride

In simple words: Hard water, which contains calcium and magnesium chlorides and sulfates, is softened by adding washing soda (\(Na_2CO_3\)), which reacts to form insoluble calcium and magnesium carbonate salts, thereby removing the hardness-causing ions and allowing lather to form.

🎯 Exam Tip: Explain that hard water contains calcium and magnesium salts. Emphasize that washing soda (\(Na_2CO_3\)) is added, leading to the formation of insoluble carbonate precipitates and the water becoming soft. Include the chemical reaction to show the process clearly.

Question 6. How is washing soda obtained from sodium carbonate?
Answer:

• Sodium carbonate is a water soluble salt of sodium.
• Crystalline sodium carbonate, on keeping, loses its water of crystallization readily and a white powder is obtained.

In simple words: Washing soda, which is crystalline sodium carbonate, is obtained by allowing it to lose its water of crystallization upon exposure to air, resulting in a white powder.

🎯 Exam Tip: Focus on the loss of "water of crystallization" from crystalline sodium carbonate when exposed to air, resulting in the formation of white powdered washing soda.

Question 7. How is soap prepared? Why it does not form lather with hard water?
Answer:

• When oil or animal fat is boiled with an aqueous solution of sodium or potassium hydroxide, sodium or potassium salts of carboxylic acids (fatty acids) are formed.
• These salts are called soap.
• When soap is mixed with hard water, calcium and magnesium salts of fatty acids are formed.
• These being water insoluble, they form a precipitate and that is why lather is not formed.

In simple words: Soap is made by boiling oils or animal fats with sodium or potassium hydroxide to form fatty acid salts; it doesn't lather in hard water because the calcium and magnesium ions in hard water react with the soap to form insoluble precipitates instead of suds.

🎯 Exam Tip: Explain soap formation as the reaction of fats/oils with strong bases. For hard water, highlight the reaction with calcium and magnesium ions to form insoluble precipitates, which prevents lathering.

Question 8. What are the harmful effects of artificial food colours?
Answer:

• Food colours added to pickles, jams and sauces contain small quantities of lead and mercury. These can be harmful for those who consume these products on a regular basis.
• Diseases like ADHD (Attention Deficit Hyperactivity Disorder) can affect children due to excessive consumption of foods with added food colours.

In simple words: Artificial food colors can be harmful as they may contain heavy metals like lead and mercury, and their excessive consumption, especially by children, has been linked to conditions such as ADHD.

🎯 Exam Tip: Mention the presence of heavy metals (lead, mercury) in some artificial food colors and their long-term health risks, including the specific link to ADHD in children.

Question 9. Which is the main source of colour for preparing a natural dye?
Answer:

• Plants are the main source of colour for preparing a natural dye.
• Roots, leaves, flowers, bark, fruits, seeds, fungus and pistils are used for making dyes.
• In Kashmir a very good dye is made from saffron, which is used to dye fibers from which saris, shawls and dresses are made.
• These are very costly. The use of henna leaves to colour hair is safe for health.

In simple words: Plants are the primary source for natural dyes, utilizing various parts like roots, leaves, flowers, and fruits, with examples including saffron from Kashmir and henna leaves, which are generally considered safe for health.

🎯 Exam Tip: Identify plants as the main source and list different plant parts used (roots, leaves, flowers, etc.). Providing examples like saffron and henna enhances the answer.

Question 10. How are artificial colours harmful to us?
Answer:

• We regularly use artificial colours on Rang Panchami.
• The red colour used on Rang Panchami is very dangerous.
• It contains a high proportion of mercury in it.
• This poses risks like blindness, skin cancer, asthma, itching of the skin, permanent blocking of sweat pores, etc.
• Therefore, it is necessary that artificial colours are used cautiously.

In simple words: Artificial colors, especially those used in festivals like Rang Panchami, can be harmful due to high mercury content, leading to severe health issues such as blindness, skin cancer, asthma, skin itching, and blocked sweat pores, hence requiring cautious use.

🎯 Exam Tip: Specifically mention the dangers of artificial colors used in festivals (like Rang Panchami's red color), attributing the harm to mercury content and detailing the range of severe health problems they can cause.

Question 11. What are the harmful effects of deodorants?
Answer:

• Aluminium - Zirconium compounds are the most harmful chemicals in deodorants. Disorders like headache, asthma, respiratory disorders, heart disease are likely to occur without our knowledge.
• There is a possibility of various skin disorders and also skin cancer due to the aluminium chlorohydrates.

In simple words: Deodorants contain harmful chemicals like aluminum-zirconium compounds and aluminum chlorohydrates, which can lead to various health issues such as headaches, asthma, respiratory problems, heart disease, skin disorders, and even skin cancer.

🎯 Exam Tip: Pinpoint specific harmful ingredients like aluminum-zirconium compounds and aluminum chlorohydrates. List a diverse range of health issues, including respiratory, cardiovascular, and dermatological problems.

Question 12. How is a ceramic article made?
Answer:

• When clay is kneaded in water, shaped and then fired in a kiln at a temperature of 1000 to 1150 °C, a porous ceramic is formed.
• To overcome the porosity, the fired object is covered with finely ground glass powder suspended in water (glaze) and is then fired again. As a result, the surface of the ceramic becomes shiny and its porosity disappears.

In simple words: Ceramic articles are made by kneading clay with water, shaping it, and firing it in a kiln at 1000-1150°C to create a porous ceramic; this porosity is then eliminated and a shiny surface achieved by applying a glass powder glaze and re-firing.

🎯 Exam Tip: Describe the process sequentially: kneading clay, shaping, initial firing (mentioning temperature), and then the glazing step (applying glass powder and a second firing) to achieve a non-porous, shiny surface.

Question 13. What is porcelain? How is it made?
Answer:1. Porcelain is a hard, translucent and white coloured ceramic. It is made by using the white clay called kaolin, found in China. Glass, granite and the mineral feldspar is mixed with kaolin and kneaded with water.
2. The resulting mixture is shaped and fired in a kiln at a temperature of 1200 to 1450 °C. On firing again after glazing, beautiful articles of porcelain are obtained.In simple words: Porcelain is a hard, translucent, white ceramic made by kneading kaolin clay with glass, granite, and feldspar and water, then shaping and firing it in a kiln at 1200-1450°C, often with a second firing after glazing to create beautiful articles.

🎯 Exam Tip: Define porcelain by its key characteristics (hard, translucent, white ceramic). Detail its composition (kaolin, glass, granite, feldspar) and the two-stage firing process (initial firing and post-glazing firing with temperature ranges).

Answer The Following Questions:

Question 1. What are the constituents of baking powder? Where is the baking powder used?
Answer:

• Baking powder consist of 30% sodium bicarbonate, 5-12% monocalcium phosphate and 21-26% sodium aluminium sulphate.
• Baking powder is a leavening agent and is used for increasing the volume and lightening the texture of baked goods.

In simple words: Baking powder is composed of sodium bicarbonate, monocalcium phosphate, and sodium aluminum sulphate, and its primary use is as a leavening agent to make baked goods light and voluminous.

🎯 Exam Tip: List the three main constituents of baking powder along with their approximate percentages. Clearly state its function as a leavening agent and its effect on baked goods (increasing volume and lightening texture).

Question 2. Take a piece of coloured cloth. Put some saturated solution of bleaching powder on a small part and observe what changes take place in the colour of the cloth.
Answer:When bleaching powder is added to a piece of coloured cloth, the fabric looses its colour due to the oxidising reaction of the chlorine present in the bleaching powder.In simple words: When bleaching powder is applied to colored cloth, the chlorine within it undergoes an oxidizing reaction, causing the fabric to lose its color.

🎯 Exam Tip: The key observation is the loss of color. Explain this by attributing it to the "oxidizing reaction of chlorine" present in bleaching powder.

Answer In Detail:

Question 1. Give the properties and uses of Sodium chloride.
Answer:Properties and uses of sodium chloride:

• Common salt is a colourless and crystalline ionic compound. There is no water of crystallization in its crystalline structure.
• It is a neutral salt, salty in taste.
• This compound is used for the production of salts like Na2CO3, NaHCO3.
• When an electric current is passed through a saturated solution of sodium chloride (brine), it is electrolysed and hydrogen gas is released at the cathode while chlorine gas is released at the anode.
• This method is used for production of chlorine gas. In this method an important basic compound NaOH is formed in the cell.
• 2NaCl + 2H2O \(\implies\) 2NaOH + Cl2\( \uparrow \) + H2\( \uparrow \)
• When salt is heated to a high temperature (about 800 °C), it melts. This is called the fused state of the salt.
• When fused salt is electrolysed, chlorine gas is released at the anode and liquid sodium metal, at the cathode.

In simple words: Sodium chloride, a colorless, crystalline ionic compound with a neutral pH and salty taste, is used as common salt, to produce other salts like washing soda and baking soda, and in the electrolysis of brine or fused salt to yield chlorine gas, hydrogen gas (from brine), and sodium hydroxide or liquid sodium metal (from fused salt).

🎯 Exam Tip: List both physical (colorless, crystalline, salty, neutral pH) and chemical (ionic, no water of crystallization) properties. For uses, cover its role as common salt, in chemical synthesis (Na2CO3, NaHCO3), and in industrial electrolysis, including the specific products and relevant chemical equations.

Question 2. Give the properties and uses of Bleaching Powder.
Answer:Properties and uses bleaching powder:

• Bleaching powder is a yellowish-white coloured solid substance.
• Its chemical name is Calcium oxychloride.
• It has a strong odour of chlorine gas.
• It is used for disinfection of drinking water at the water works and the water in the swimming pool.
• It is used for bleaching of cloth.
• It is used for disinfection by the road side and garbage sites.
• Dilute sulphuric acid and dilute hydrochloric acid react rapidly with bleaching powder to release chlorine gas completely.
  CaOCl2 + H2SO4 \(\implies\) CaSO4 + Cl2 \( \uparrow \) + H2O
  CaOCl2 + 2HCl \(\implies\) CaCl2 + Cl2 \( \uparrow \) + H2O
• Calcium oxychloride reacts slowly with carbon dioxide to form calcium carbonate and chlorine.
  CaOCl2 + CO2 \(\implies\) CaCOs + Cl2 \( \uparrow \)

In simple words: Bleaching powder is a yellowish-white solid, chemically known as calcium oxychloride, with a strong chlorine odor, used extensively as a disinfectant for water and waste, and for bleaching cloth; it reacts with acids and carbon dioxide to release chlorine gas, demonstrating its strong oxidizing properties.

🎯 Exam Tip: Begin with its physical properties (color, odor) and chemical name (calcium oxychloride). List various uses as a disinfectant and bleaching agent. Crucially, include the reactions with dilute sulfuric acid, hydrochloric acid, and carbon dioxide, showing the release of chlorine gas for each.

Question 3. Explain with neat labelled diagram the nature of radioactive radiation.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक विद्युत क्षेत्र में रेडियोधर्मी विकिरणों के विचलन को दर्शाता है। एक लेड ब्लॉक में रखे रेडियोधर्मी पदार्थ से निकलने वाली किरणें दो विपरीत आवेशित प्लेटों से होकर गुजरती हैं। ऋण आवेशित प्लेट की ओर थोड़ा विचलित होने वाली किरणें अल्फा किरणें होती हैं, जबकि धन आवेशित प्लेट की ओर पर्याप्त रूप से विचलित होने वाली किरणें बीटा किरणें होती हैं। गामा किरणें अविचलित सीधी रेखा में गुजरती हैं, जिससे यह पता चलता है कि वे अनावेशित विद्युतचुंबकीय विकिरण हैं।

• When radioactive radiations are allowed to pass through two oppositely charged plates they get separated. This method was introduced by Rutherford in 1902.
• Rutherford and Willard studied the radiation emitted by radioactive substances.
• For this purpose, the rays were allowed to pass through an electrical field and a photographic plate was held in their path.
• It was found that the radiation was divided into three types.
• One type of radiation deviated slightly towards the negatively charged plate, while the second type of radiation deviated substantially towards the positively charged plate.
• However, the third type of radiation did not deviate at all in the electrical field.
• The rays which deviated slightly toward negatively charged plate are called alpha rays.
• Those which deviate substantially towards the positively charged plate are called beta rays and those which did not deviate at all are called gamma rays.

In simple words: In Rutherford's experiment, radioactive radiations passing through an electric field split into three types: alpha rays (positively charged) which deflect slightly towards the negative plate, beta rays (negatively charged) which deflect significantly towards the positive plate, and gamma rays (uncharged electromagnetic radiation) which pass straight through without deflection.

🎯 Exam Tip: Describe Rutherford's experiment setup, including the electric field and photographic plate. Clearly differentiate between alpha, beta, and gamma rays based on their charge and deflection patterns (slight negative, substantial positive, no deflection respectively).

Question 4. Give the characteristics of alpha, beta and gamma rays.
Answer:Characteristics of alpha, beta and gamma rays are as given in the table.

Sr. No.	Properties	Alpha rays (\(\alpha\))	Beta rays (\(\beta\))	Gamma rays (\(\gamma\))
(i)	Nature	Current of alpha (He++) particles	Current of beta (e-) particles	Electromagnetic radiation
(ii)	Mass	4.0028 u	0.000548 u	No mass
(iii)	Charge	+2	-1	Electrically neutral
(iv)	Velocity	1/5 to 1/20 times the velocity of light	1/5 to 9/10 times the velocity of light	Same as the velocity of light
(v)	Deviation in the electric field	Attracted towards negatively charged plate	Attracted towards positively charged plate	Not deviated
(vi)	Penetrating power	Can penetrate an aluminium sheet of thickness < 0.02 mm	Can penetrate an aluminium sheet of thickness 2 mm, which is 100 times the penetration of alpha particles.	Can penetrate 15 cm thick lead screen which is 10,000 times the penetration of alpha particles
(vii)	Ionization power	Very high	Low	Very Low
(viii)	Power to produce fluorescence	Very high	Very low	Low

In simple words: Alpha rays are positively charged helium nuclei with high mass and very high ionization power, deflected towards the negative plate; beta rays are negatively charged electrons with very low mass and moderate ionization power, deflected towards the positive plate; and gamma rays are uncharged electromagnetic radiation with no mass, extremely high penetrating power, and no deflection.

🎯 Exam Tip: Present the characteristics in a comparative table format. Ensure you cover nature, mass, charge, velocity, deflection in electric field, penetrating power, ionization power, and fluorescence. Accuracy in values (e.g., charge, relative penetration) is important.

Question 5. Give the uses of radioactive isotopes in Medical science.
Answer:Medical science:

• Polycythemia: The red blood cell count increases in the disease polycythemia. Phosphorus-32 is used in its treatment.
• Bone cancer: Strontium-89, strontium-90, samarium-153 and radium-223 are used in the treatment of bone cancer.
• Hyperthyroidism: Enlargement of thyroid gland, weight loss in spite of appetite, insomnia are the symptoms of hyperthyroidism.
• It occurs due to overproduction of hormones by the thyroid gland. Iodine-123 is used in the treatment of hyperthyroidism.
• Tumour detection: Boron-10, iodine-131, cobalt-60 are used in treatment of brain tumour, while arsenic-74 is used in detection of small tumours in the body.

In simple words: Radioactive isotopes are vital in medical science for treating various conditions: phosphorus-32 for polycythemia, strontium-89, -90, samarium-153, and radium-223 for bone cancer, iodine-123 for hyperthyroidism, and boron-10, iodine-131, cobalt-60, and arsenic-74 for tumor detection and treatment.

🎯 Exam Tip: Organize the uses by specific diseases/conditions (polycythemia, bone cancer, hyperthyroidism, tumor detection). For each, name the specific radioactive isotope(s) used and briefly explain their role in diagnosis or treatment.

Question 6. What are the hazards of radioactive substances and radiation?
Answer:

• The central nervous system is affected by radioactive radiations.
• Hereditary defects are generated by bombardment of radiation on D.N.A in the body.
• Radioactive radiation can penetrate the skin, and causes diseases like skin cancer, leukemia.
• The radiative pollutants created due to explosions enter the body through air and it is difficult to control them.
• The radioactive pollutants released in the sea enter the bodies of fishes and through them enter the human body.
• The radioactive paint on the watch can cause cancer.
• The radioactive isotopes strontium-90 can enter the body through plants, fruits, flowers, cereals, milk, etc. and cause diseases like bone cancer, leukemia.

In simple words: Radioactive substances and radiation pose severe health hazards, including damage to the central nervous system, genetic defects from DNA damage, skin cancer, and leukemia, with pollutants entering the body through air, sea food, and contaminated food sources like plants and milk.

🎯 Exam Tip: Enumerate the various hazards clearly, distinguishing between direct effects on the body (CNS, DNA damage, skin cancer, leukemia) and environmental pathways of contamination (air, sea, food chain). Mention specific isotopes like strontium-90 for added detail.

Question 7. Why are deodorant used? Give their types and content.
Answer:

• Body odour is caused by the bacterial decomposition of the sweat. A deodorant is used to prevent this odour.
• Deodorants contain parabens (methyl, ethyl, propyl, benzyl and butyl) and also alcohol in large proportions. Aluminium compounds and silica are also used.
• Types of deodorants are :
  (a) Ordinary deo: It contains a smaller proportion of aluminium. It decreases the odour of the sweat.
  (b) Antiperspirant deo : This decreases the extent of sweating. It contains about 15% of aluminium chlorohydrate. It clogs the sweat pores on the skin.
  (c) Clinical deo : Some people sweat heavily and it has harmful effects on the skin. Clinical deo is meant for such people. It contains 20 to 25% aluminium. It is used during the night.

In simple words: Deodorants are used to prevent body odor, which is caused by bacterial decomposition of sweat, and typically contain parabens, alcohol, and aluminum compounds; they come in types like ordinary deo (less aluminum, reduces odor), antiperspirant deo (about 15% aluminum chlorohydrate, reduces sweating by clogging pores), and clinical deo (20-25% aluminum, for heavy sweaters, used at night).

🎯 Exam Tip: Explain the cause of body odor. List common ingredients (parabens, alcohol, aluminum compounds, silica). Differentiate clearly between the three types of deodorants (ordinary, antiperspirant, clinical) by their aluminum content, mechanism of action (odor reduction vs. sweat reduction), and typical usage.

Question 8. Explain how powder coating is done.
Answer:

• Powder coating is a method of applying a layer harder than paint on the surface of an iron object to prevent rusting.
• In this method, a polymer resin, a pigment and some other ingredients are melt, mixed, cooled and ground into a uniform powder.

In simple words: Powder coating involves melting, mixing, cooling, and grinding polymer resin, pigment, and other ingredients into a fine powder. This powder is then electrostatically sprayed onto a polished metal surface, where it adheres due to the electric charge. The coated object is then heated in an oven, causing a chemical reaction that forms durable, cross-linked polymeric chains, resulting in a hard, attractive, and long-lasting finish resistant to rust.

🎯 Exam Tip: Detail the entire powder coating process: (1) preparation of the powder (melting, mixing, cooling, grinding), (2) application via electrostatic spray deposition (ESD) and charge attraction, (3) heating in an oven, and (4) the resulting chemical reaction forming polymeric chains. Mention the benefits (durability, hardness, rust prevention) and diverse applications (plastic, MDF, iron).