Selina Concise Solutions for ICSE Class 6 Chemistry Chapter 1 Introduction to Chemistry

Points To Remember

1. Science: “Science is the systematic effort by human being to study, understand and utilise nature for meaningful purposes. This understanding is slowly developed by careful observations and experiments.”

2. Chemistry: “The branch of science that deals with the study of the composition, physical and chemical properties of various forms of matter is called chemistry.”

3. Fertilisers: “Are the chemicals which provide nutrients to crops and increase their yield.” e.g. Urea, calcium nitrate, sodium nitrate, potash, ammonium sulphate etc.

4. Pesticides: “Are the chemicals used to kill pests which affect the production of crops and fruits.” e.g. Aldrin, malathion, parathion etc.

5. Insecticides are the chemical used to kill insects, e.g. D.D.T. and B.H.C.

6. Fungicides are substances which protect the crops from fungi, e.g. Bordeaux mixture and sulphur act as fungicides.

7. Hormones are group of chemicals secreted in our body to control various activities.

8. Enzymes are the chemicals secreted by our body and react with food water and oxygen as raw material in mouth and intestines.

9. Role of Chemistry: Without chemistry our life would have been dull, it has helped us in every field of life. The production of better and faster crops to meet the needs of such a huge population is possible only because of chemicals produced by chemistry, i.e. Pesticides, fungicides, insecticides preservatives help us to preserve food in a better state and of good taste for a long time.
In Industry: paints, drugs, fibres, soap, toothpaste, dyes plastics even fuels, atomic energy, petrol, diesel, kerosene, wax, paraffin rubber, acids, alkalies metals alloys are the gift of chemistry.
Medicines: Penicillin, Tetracycline, pain killers and various other antibiotics are used to kill germs and cure diseases. Building and Daily Life: Building materials, items of daily use like, ink, pen, glass, sugar, common salt, paper.

10. Preservatives are the chemicals which maintain the taste for longer time and do not let the food degrade to produce obnoxious (unpleasant smell), e.g. sugar, common salt, sodium benzoate and sodium meta-bisulphate.

Exercise

Question 1: Give two examples for each of the following substances:
(a) food preservatives
(b) fuel
(c) fungicides
(d) medicines
(e) building materials
(f) chemical war weapons

Answer:
Two examples of :
(a) Food preservatives :
1. Sodium Benzoate
2. Sodium metabisulphate
3. Sugar
4. Common salt
(b) Fuel:
1. L.P.G.
2. Petrol
3. Coal
(c) Fungicides :
1. Sulphur
2. Bordeaux mixture
(d) Medicines :
1. Penicillin
2. Painkillers
3. Antibiotics
(e) Building materials :
1. Cement
2. Steel
3. Glass
(f) Chemical war weapons :
1. TNT
2. RDX
Chemistry provides us with specific substances for different needs like protecting food or building homes. Understanding these categories helps us see how chemical science is applied in our everyday surroundings.
Teacher's Tip: Think of substances in your kitchen (sugar/salt) to remember natural preservatives easily.
Exam Tip: When asked for two examples, always try to provide the most common ones like Petrol for fuel or Cement for building materials for better clarity.

Question 2: Give short answers :
(a) What is science ?
(b) What is chemistry ?
(c) What is a fuel ?
(d) How is chemistry helpful in improving the health of human beings ?
(e) What is alchemy?
(f) What kind of experiments did Alchemists do?
(g) What is ‘Philosopher’s stone’ ?
(h) What is the main difference between alchemy and chemistry?
(i) Name the chemicals which help in increasing food production.
(j) Name six such products, which we use daily.
(k) How is the knowledge of chemistry important to mankind ?

Answer:
(a) SCIENCE is the systematic effort by human beings to control nature through experiments and observation for their own use.
OR
SCIENCE is the systematic ongoing effort by human beings to study understand and utilise nature for meaningful purposes. This understanding is slowly developed by careful observations and experiment.
(b) Chemistry : “The branch of science that deals with the study of the composition and the physical and chemical properties of various forms of matter is called Chemistry.”
(c) Fuels : The substances which on burning produce heat energy are called fuels.
(d) Chemistry is very helpful in improving the health of human beings by providing Antibiotics, Pain killers, Pencilin, Tetracycline etc. It has provided us with Vitamins, Enzymes, Minerals and Anesthesia (chloroform, formalene etc.)
(e) The word “Alchemy” has its origin in a Greek word ‘Khemeia’ means “art of transmuting metals”. It was partly based on experimentations and partly on spiritual discipline.
(f) ‘Alchemists’ considered to be early chemists. They used all general techniques of chemistry in healing humans. Their contribution proved valuable to the society and in the advancement of civilization.
They had contributed to an incredible number of future uses of chemicals, metals, ink, paints, cosmetic, medicines, porcelain, etc.
(g) The goal of alchemy was to find a mythical and magical substance called “philosopher’s stone” not a literal stone but wax, liquid or powder with magical power, which on heating with a base, iron and copper metals would turn into gold, the purest form of matter which would bring wealth, health and immortality.
(h) Alchemy was both scientific and spiritual. Alchemists never separated them. It also lacked a common language for its concepts and processes i.e. there was no standardized scientific practice.
Chemistry was completely separated from ancient traditional alchemy. Still modern chemistry in general owes a great deal to alchemy. Alloys are formed by mixing metals with other metals and substances.
(i) Chemicals which help in increasing food production are fertilisers like urea, sodium nitrate, potash, ammonium phosphate, calcium nitrate etc. Pesticides like aldrin, malathion which are used to kill pests. Insecticides like D.D.T., B.H.C. fungicides like sulphur, bordeaux mixture etc.
(j) Six products of daily use are soap, paints, pen, tooth-paste, cooking oil, potable water.
(k) Importance of chemistry to mankind chemistry plays an important role to provide us with things of daily use like toothpaste, soap, detergents, paints, clothes, medicines, fertilisers, pesticides, plastics, in preparing fuels, consumer products like glass, paper, pencils, pens, in substances used in defence like gunpowder, T.N.T. etc.
Chemistry is the foundational science that allows us to create medicines and improve food production. It has evolved from ancient practices like alchemy into the rigorous scientific study we use today to sustain modern life.
Teacher's Tip: Remember Alchemy as the "Ancient Art" and Chemistry as the "Modern Science."
Exam Tip: For definitions like Science or Chemistry, use keywords like "systematic," "matter," and "properties" to ensure a complete answer.

Question 3: What is the contribution of chemistry in the following fields ?
(a) Industry
(b) Clothings
(c) Cosmetics
(d) National Defence
(e) Medicines

Answer:
Contribution of chemistry in the field of :
(a) Industry : To improve efficiency and production of metals, paints, paper, plastics, alloys, textile, pharmaceuticals, electroplating, cosmetics, synthetic fibres etc.
(b) Clothings: Chemistry is widely used in textile industry which manufactures clothing for us. Clothes guard our body from external environment.
Formation of clothing begins with the knowledge of conversion of fibres into fabrics. Fibres can be natural or synthetic. Earlier only natural fibres were known to man such as cotton, jute, silk, wool, etc. which were used to produce dress materials, sarees, bags, sweaters, shawls, etc. With more development, synthetic fibres were also made such as nylon, terylene etc. These fibres are strong, wrinkle resistant and dry quickly. They are used to make towels, bed sheets, bags, curtains, carpets, blankets, dress materials, etc.
(c) Cosmetics: The use of talcum powder, skincare creams, lipsticks, eyes and facial make up, deodorants, lotions, perfumes, bathing oil, body butter, baby products, etc. It is possible to convert various ingredients into usable cosmetics due to knowledge of chemistry.
(d) National Defence : Substances like gunpowder, T.N.T. (trinitrotoluene), phosgene, chemical weapons, laughing gas, etc., are all products of chemistry which contribute to the national defence.
(e) Medicines : Extensive researches by chemists have led to the discovery of number of medicinal drugs. These drugs help in fighting diseases and have thus increased the life span of human beings.
Examples : Aspirin, paracetamol, antibiotics like penicillin, tetracyline, antiseptics and various other medicines used to kill germs and cure diseases and their symptoms.
Chemistry is essential for creating the materials we use daily, from the clothes we wear to the medicines that keep us healthy. It also plays a vital role in protecting a country through advanced materials for national defence.
Teacher's Tip: Link synthetic fibres like Nylon to the word "Chemistry" to remember that man-made fabrics are chemical products.
Exam Tip: Mentioning specific examples like T.N.T. for defence or Aspirin for medicines shows a deeper understanding and fetches better marks.

Question 4: Who is known as Father of chemistry? Why?

Answer:
Robert William Boyle is known as ‘Father of Modern Chemistry’. He was an Anglo Irish scientist born in Ireland. He was the first to perform experiments under controlled conditions and publish his researches with elaborate details of procedure, apparatus and observations. Robert Boyle put chemistry on a firm scientific footing transforming it from alchemy into one based on measurements. He defined elements, compounds and mixtures.
Robert Boyle changed chemistry from a magical practice into a real science based on facts and experiments. His work laid the foundation for how we study different substances as elements or compounds today.
Teacher's Tip: Think of "Boyle" as the person who made chemistry "Boil" with scientific experiments!
Exam Tip: Include the phrase "firm scientific footing" to highlight why he earned the title of Father of Modern Chemistry.

Question 5: Name the scientists who discovered the following.
(a) Atoms
(b) Oxygen
(c) Safety lamp
(d) Elements

Answer:
The scientists who discovered
(a) Atoms : John Dalton was a British chemist and physicist. He proved that matter consists of small indivisble called ‘atoms’. For this he proposed the atomic theory which was later on called “Dalton’s atomic theory”.
(b) Oxygen : Joseph Priestly.
(c) Safety lamp : Sir Humphry Davy.
(d) Elements : Antoiene Lavoisier was a French nobleman. He revolutionized chemistry. Lavoisier named the elements carbon, hydrogen and oxygen and discovered the role of oxygen in combustion and respiration for which he is most noted. He established that water is a compound and helped to continue the transformation of chemistry from a qualitative science to a quantitative one.
These scientists each made a specific discovery that changed how we see the world, such as identifying the tiny particles that make up matter. Their work turned chemistry into a science of measuring and naming different parts of nature.
Teacher's Tip: Use the initials J.D. for John Dalton - Atoms to remember the connection quickly.
Exam Tip: When writing about Lavoisier, remember to mention that he named oxygen to emphasize his contribution to the language of chemistry.

Objective Type Questions

Question 1: Fill in the blanks :
(a) Chemistry deals with the study of matter and the changes it undergoes.
(b) Fertilizers help to increase the production of food.
(c) Food items like jams and pickles are protected by using preservatives (salt and sugar).
(d) $L.P.G.$ is used for fuel.
(e) Inert gases were discovered by William Ramsay.

Question 2: Match the following words in column A with those in column B:
Column A - Column B
(a) Clothing - (ii) nylon, wool
(b) Green revolution - (iii) agriculture
(c) Building materials - (iv) mortar, cement
(d) Commodities of daily use - (i) toothpaste, cosmetic
Answer:
(a) - (ii)
(b) - (iii)
(c) - (iv)
(d) - (i)
This matching exercise connects chemical products to the specific area of life they improve. It is a quick way to review how diverse chemistry's impact is on society.
Teacher's Tip: Associate "Green" in Green Revolution with plants and agriculture.
Exam Tip: Double-check each pair to make sure there isn't a better match before finalizing.

Question 3: Write “True” or “False” against each of the following statements.
(a) Chemistry plays an important role in national economy: True
(b) Antibiotics are used as preservatives : False
(c) $D.D.T.$ is an important fertiliser: False
(d) Gunpowder is an ……ticide : False
(e) Enzymes secreted by our body are chemicals : True

Question 4: Choose the correct alternative from the choices given below for the following statements :

(a) Trinitrotoluene is used as
1. a preservative
2. a fertiliser
3. a fuel
4. an explosive
Answer: 4. an explosive

(b) Which one of the following is a pesticide ?
1. benzoic acid
2. aldrin
3. sugar
4. gunpowder
Answer: 2. aldrin

(c) Mortar is used as a
1. plastic material
2. a building material
3. an insecticide
4. as medicine
Answer: 2. a building material

(d) Urea is an important
1. fuel
2. preservative
3. fertiliser
4. food item
Answer: 3. fertiliser

(e) The chemicals prescribed by a doctor in treatment of infectious diseases are called
1. antigens
2. lotions
3. antibiotics
4. creams
Answer: 3. antibiotics

Question 5: Match the following scientists in column A with their discoveries or contributions in column B.
Column A - Column B
(a) Marie Curie - (iii) Nobel Prize Winner (two times)
(b) John dalton - (iv) Atomic theory
(c) William Ramsey - (ii) Helium
(d) Sir Humphry Davy - (i) Safety Lamp

Answer:
(a) - (iii)
(b) - (iv)
(c) - (ii)
(d) - (i)
Matching scientists to their discoveries honors the people who made modern chemistry possible. It helps us remember the specific milestones in scientific history.
Teacher's Tip: Marie Curie is famous for being the first person to win two Nobel Prizes in different sciences.
Exam Tip: Match the most famous ones first, and the remaining ones will be easier to figure out.

Additional Questions For Practice
Exercise

Question 1: State what is Science and give the basic bifurcation of Science with reasons.

Answer:
Science is the subject which includes the study of various experiments performed by a scientist with all observations recorded and inferences concluded.
Bifurcation : Science is bifurcated into three main branches Physics, Chemistry and Biology which make study of each branch simple and more focussed.
Science is a broad field of study that uses experiments to understand how our world works. To make it easier to learn, we divide it into specific parts like Physics for energy, Chemistry for substances, and Biology for living things.
Teacher's Tip: Think of science as a big tree with three main branches: Physics, Chemistry, and Biology.
Exam Tip: Mention "observation" and "experiments" whenever you define Science to get full credit.

Question 2: Give the basic difference between Inorganic Chemistry and Organic Chemistry.

Answer:
(a) Inorganic chemistry includes study of innumerable elements and compounds
Elements include: Metals and Non metals (Sulphur, Phosphorus, Sodium, Potassium)
Gases include: SO₂, CO₂, N
Acids include: HCl, H₂SO₄, HNO₃
(b) Organic chemistry includes study of specific carbon compounds built up mainly of carbon and hydrogen
Compounds include: hydrocarbons e.g., Methane
Acids include: acetic acid
Inorganic chemistry mostly deals with non-living minerals and various elements found in nature. Organic chemistry is specifically focused on compounds that contain carbon, which are often related to living things.
Teacher's Tip: Just remember "Organic = Carbon" to distinguish between the two.
Exam Tip: Use examples like HCl for Inorganic and Methane for Organic to make your answer stand out.

Question 3: State the functions of the following basic glass apparatus.
(a) Glass test tube
(b) Hard glass boiling tube
(c) Beaker
(d) Round bottom flask
(e) Retort

Answer:
(a) Glass test tube : It is used for heating chemicals and studying reactions in chemicals solution.
(b) Hard glass boiling tube : It is resistant to chemicals and used for special purposes. It is made of pyrex.
(c) Beaker : It is used for holding pouring and mixing solutions.
(d) Round bottom flask : In preparation of gases, where heating is required. Since the flask is round bottomed, heat is uniformly distributed throughout on heating.
(e) Retort : For carrying out distillation experiments which include distillation of acids.
Each piece of laboratory glassware is designed for a specific job, such as mixing or heating. Using the right tool, like a round bottom flask for even heating, ensures that experiments are safe and accurate.
Teacher's Tip: Remember "Pyrex" means the glass is tough and can handle high heat.
Exam Tip: When explaining the Round Bottom Flask, always mention that it provides "uniform distribution of heat."

Question 4: State why a round bottom flask is preferred to a flat bottom flask - during preparation of gases in the laboratory.

Answer:
Round bottom flask is preferred to flat bottom flask because in round bottom flask heat is uniformly distributed throughout on heating.
The round shape of the flask allows the flames to touch more surface area evenly. This prevents the glass from breaking due to uneven temperatures and helps the chemical reaction happen smoothly.
Teacher's Tip: Think of a ball in a fire; the heat wraps around it perfectly because it's round!
Exam Tip: Use the word "uniformly" to explain how heat is spread in the flask.

Question 5: State the function of
(a) The wooden handle at the end of the test tube holder.
(b) The asbestos fixed at the centre of the wire gauze.
(c) The clamp mounted on the rod of a retort stand.
(d) The air regulator in a Bunsen burner.
(e) The tap at the base of a burette.

Answer:
(a) The wooden handle at the end of test tube being a poor conductor of heat, makes holding the test tube holder easy.
(b) The asbestos fixed at the centre of the wire gauze initiates even distribution of heat to the bottom of the apparatus. It also prevents glass apparatus from cracking.
(c) The clamp mounted on the rod of a retort stand helps in holding the apparatus and adjusting its level upwards or downwards.
(d) The air regulator has holes and is used for regulating the flame.
(e) The tap at the base of the burette helps in removing the measured liquid drop wise.
These parts are designed to make experiments safer and more precise for the user. For instance, wooden handles protect our hands from burns, and taps help us control liquid flow perfectly.
Teacher's Tip: Asbestos is like a "heat spreader" for your lab equipment.
Exam Tip: Mention "poor conductor of heat" when explaining why handles are made of wood or plastic.

Question 6: State the method used for collecting the following gases-
(a) Oxygen – a gas slightly soluble in water.
(b) Ammonia – a gas highly soluble in water and lighter than air.
(c) Sulphur dioxide – a gas highly soluble in water and heavier than air.

Answer:
(a) The method used for collecting oxygen gas is downward displacement of water. In this method, the gas jar is filled with water and inverted over the beehive shelf, so that the water is displaced downwards and oxygen is collected upwards.
(b) The method used for collecting ammonia gas is downward displacement of air. This method is used for gases like ammonia which is soluble in water and lighter than air.
(c) The method used for collecting SO₂ is upward displacement of air. This method is used for gases like SO₂ which is soluble in water and heavier than air.
Collecting gases depends on whether they sink or float in air and if they dissolve in water. We use the "displacement" method to push out the air or water and capture the gas we want.
Teacher's Tip: If it's lighter than air, it pushes air DOWN (Downward displacement). If it's heavier, it pushes air UP!
Exam Tip: Be careful with the terms "upward" and "downward" displacement; always link them to the gas's weight compared to air.

Question 7: Explain in brief the importance of Chemistry in agriculture and production of various products.

Answer:
Importance of Chemistry : In agriculture end products and as follow :
1. AGRICULTURE
(a) Fertilizers – A substance to improve fertility and supply of nutrients to plant and is essential for growth.
Example :
1. Ammonium nitrate – widely used as a fertilizer.
2. Urea – an important source of nitrogen [non-explosive ‘ and solid in nature]
3. Phosphatic fertilizer – super phosphates. About 90% of fertilizers are in the solid form. Liquid fertilizers comprise – aqueous solutions of ammonia or ammonium nitrate.
(b) Pesticides
1. Chemicals added to the soil, to kill pests. They include – Herbicides; insecticides; termiticides etc.
2. Pesticides protect the plants from – weeds, fungi and insects.
3. About 30% of crops are destroyed by agricultural pests.
(a) Herbicides – Rill or inhibit growth of – unwanted plants.
(b) Insecticides – Destroy insects, which harm or destroy plants. Pesticides may come in contact with other living organisms and disrupt the balance of the eco-system.
2. PRODUCTS
Knowledge of Chemistry has initiated production of – different products
1. Food – Refined oils, butter, cheese, etc. are obtained through chemical reactions.
2. Construction– Mortar, cement, glass, etc. are various chemical compounds.
3. Clothing – Natural fabrics such as silk are made through chemical reactions.
4. Household – Cooking gas which is liquefied petroleum gas or $LPG$, food preservatives, specific utensils and electronic items, all involve use of Chemistry.
5. Daily usage – Paints, dyes, perfumes, paper, ink etc. involve chemical reactions.
6. Industrial – Metals & alloys [mixture of metals] which find application in innumerable machines and metallic structures like automobiles, involve Chemistry.
7. Petrolium – Petrol, kerosene & diesel oil are products – obtained from petroleum
Chemistry is the backbone of food production as it provides the nutrients needed for crops to grow and the protection they need from pests. Beyond the farm, chemical science allows us to manufacture everything from construction materials to household fuels like $LPG$.
Teacher's Tip: Think of Fertilizers as "Plant Vitamins" and Pesticides as "Plant Shields."
Exam Tip: Always list specific categories like "Industry" or "Food" to organize a long answer about chemistry's importance.

Question 8: ‘Alchemists are older words for Chemists’. Discuss the statement in brief.

Answer:
Alchemy and alchemists are older words for Chemistry and chemists where – alchemists transformed or created substances through a seemingly – magical process. An alchemists Nicolas flamel claimed to transform metals into gold.
Alchemists were like the ancestors of modern chemists, though they often mixed science with magic. While they failed to turn lead into gold, their experiments with metals and liquids led to many of the scientific techniques we still use.
Teacher's Tip: Imagine alchemists as the "wizards" who eventually became the "scientists" of today.
Exam Tip: Mention the name "Nicolas Flamel" to add historical value to your discussion.

Question 9: In the medieval ages – philosopher’s stone was connected with all transformations. Explain.

Answer:
In the medievel ages to the 17th Century the so-called philosopher’s stone – held priority and alchemists were successful to a certain extent, in the development of processes, which helped later chemists to extract metals and develop – path-breaking avenues in Chemistry. The scientific process involving modern chemistry started poving paths and chemistry regains its rightful position.
The philosopher's stone was a legendary substance that alchemists believed could change common metals into gold. This quest pushed them to invent tools and methods that eventually became the basis for modern chemistry experiments.
Teacher's Tip: The "Stone" wasn't always a rock; it was sometimes described as a magic powder or potion.
Exam Tip: Clarify that while the stone was mythical, the search for it led to real scientific progress.

Question 10: State the contributions of
(a) Dimitri Mendeleev
(b) Antoine Lavoisier
(c) John Dalton – towards the development of Chemistry.

Answer:
(a) Dimitri Mendeleev
He formulated the – Periodic Table of elements.
1. He systematically arranged the dozens of known element by atomic weights and could even predict the properties of the still unknown elements.
2. He devised the Periodic Table. He was best known for his discovery of the – Periodic Law.
(b) Antoine Lavoisier
1. He recognised and named oxygen in 1778 & later – hydrogen in 1783.
2. He also wrote the first extensive list of elements and helped to reform chemical nomenclature.
3. In 1774, he turned his attention to the phenomenon of combustion with his famous experiment, in which he heated pure mercury in a swan necked retort, leading to the discovery of oxygen.
(c) John Dalton
1. He compiled his theory in 1803 known as Dalton’s atomic theory.
2. The main postulates of Dalton’s atomic theory are that “Matter consists of particles called atoms, which are indivisible and cannot be created or destroyed.”
3. The theory was later contradicted in certain aspects by the Modem atomic theory.
These three scientists organized the chaos of substances into a logical system using tables, names, and atomic theories. Their work allowed future scientists to predict how elements would behave even before they were fully discovered.
Teacher's Tip: Mendeleev is the "Map-maker" of elements; he gave us the Periodic Table.
Exam Tip: When writing about Dalton, highlight that he viewed atoms as "indivisible" particles.

Question 11: Differentiate between the terms – food preservatives and food processing with appropriate examples.

Answer:
Food preservatives – are substances or chemicals – added to food or beverages to:
1. Prevent decomposition by bacteria or microbes.
2. Reduce risk of food borne infections.
3. Preserve nutritional quality of food.
Example Table:
Preservative - Food Item
Benzoic acid - Jams, pickles, carbonated drinks.
Nitrates - Meat products
Sulphur compounds - Beverages, wines etc.
Food processing involves changing raw ingredients into a form we can buy and use, like turning wheat into flour or mincing meat. Preservatives are just one tool used during processing to make sure that food stays safe for a long time on the shelf.
Teacher's Tip: Processing is the "Action" (like cooking), and preservatives are the "Ingredients" added to keep it fresh.
Exam Tip: Provide a table format for examples to make your answer clearer and more professional.

Question 12: Explain the term ‘cosmetics’ ‘talc’. Name a few main ingredients in cosmetics the role they play.

Answer:
Cosmetics are mixtures of chemical compounds from natural sources or from synthetic sources. Cosmetics – enhance or alter the appearance or fragrance of an individual. Some sources of compounds used in cosmetics include – modified natural oils and fats, processed minerals e.g. – zinc oxide, iron oxide and talc.
Talc :
1. Talcum powder is made from talc – a mineral made up of – hydrated magnesium silicate, (contains elements – magnesium silicon, oxygen).
2. In its natural form – talc contains asbestos – which is removed from consumer products.
3. Talc – absorbs moisture, cuts down on friction, keeps skin dry and prevents rashes.
Cosmetics are used to change how we look or smell using safe chemical mixtures. Talc is a very common mineral ingredient that is excellent at absorbing sweat and keeping our skin smooth.
Teacher's Tip: Think of Talc as a "Sponge for moisture" on your skin.
Exam Tip: Mention "Zinc oxide" as an example of a mineral used in cosmetics to show extra knowledge.

Question 13: Differentiate between – natural fibres & synthetic fibres. State what is – Terylene. State some of its characteristic properties which make it suitable for commercial use.

Answer:
Natural fibres – such as cotton and wool which were directly converted into clothing material.
Synthetic fibres – such as terylene, nylon and rayon are used in expensive clothing ; carpets etc.
Terylene : It is a synthetic polyester fibre or fabric formed generally, by – addition of polyester to natural fibre – cotton. The combination makes the fabric, easy to clean and crease resistant.
2. Properties – It is a strong fabric
(a) elastic in nature, resistant to friction,
(b) suffers little loss in strength,
(c) crease resistant,
(d) easily washable and dries quickly.
3. Uses
(a) in fashion garment fabrics
(b) in nonwoven carpets, rain coats, sails .
(c) in making of nets, ropes, hoses etc.
Natural fibers come from plants or animals, while synthetic fibers are created by scientists in labs. Terylene is a popular synthetic fabric because it doesn't wrinkle easily and lasts a very long time compared to natural cotton.
Teacher's Tip: If your clothes dry very fast after washing, they are probably made of synthetic fibers!
Exam Tip: List "crease resistant" as a top property of Terylene, as it's its most famous benefit.

Question 14: Explain how medicines are a boon to mankind. State the positive & negative effects of medicines like aspirin and paracetamol.

Answer:
Medicines are natural or synthetic substances which when taken in a living body, affects its functioning, and treats or prevents a disease.
Aspirin - Positive effect :
1. It is a medicine to treat pain, fever and inflammation.
2. Aspirin given shortly after a heart attack, may decrease risk of death.
3. As long term use it may reduce, blood clots in people who are at a high risk.
Negative effect :
1. It is generally not recommended in children with infections.
2. Its side effects may include upset stomach, stomach ulcers etc.
Paracetamol:
1. It is a medicine to treat mild to moderate pain and fever.
2. It may also be used in low back pain, headaches and for dental use.
Negative effect :
1. It maybe sold in combination with cold medications.
2. It is safe at recommended doses, but too high a dose may result in liver problems.
Medicines help humans live longer by curing infections and reducing pain. However, even common pills like Aspirin must be used carefully because they can cause stomach issues or liver damage if taken incorrectly.
Teacher's Tip: Medicines are like tools; they work great when used right but can be dangerous if misused.
Exam Tip: Always distinguish between "Positive" and "Negative" effects when discussing drugs like Paracetamol.

Question 15: Give a comparitive difference between soaps and detergents. Give a reason why detergents have an advantage over soap.

Answer:
Soaps are substances used with water, for cleaning and washing and are made from a compound of vegetable oils or animal fats along, with sodium or potassium hydroxide and generally have perfumes or colourants, added to it. Whereas Detergents are synthetic water soluble cleaning agents that unlike soap (which are prepared from vegetable oils or fats) are prepared from petroleum products along with sodium or potassium hydroxide.
Detergents have an advantage over ordinary soap:
1. Hard water is one which does not lather with soap, while soft water lathers easily.
2. Ordinary soap when rubbed in hard water is wasted and lather forms only after all the insoluble salts in hard water are removed as scum.
3. Synthetic detergents do not form scum and lather even in hard water.
Soap is made from natural fats, while detergents are man-made from petroleum. Detergents are better for cleaning because they work well even in "hard water" where soap fails to make bubbles.
Teacher's Tip: Detergents are the "Super-cleaning" cousins of regular soap.
Exam Tip: Mention "hard water" and "scum" to explain why detergents are more efficient than soap.

Question 16: State what are – ‘stain removals’. Name three important stain removers & give their prime functions.

Answer:
Stain removals It is the process of removing a mark or a stain left by one substance on a specific surface fabric. Most stains are removed by dissolving with a solvent.
Examples of stain removers:
1. Lemon juice - contains citric acid and is used for removing stains from fabrics.
2. Hydrogen peroxide - a mild bleaching agent also effective in removing stains.
3. Glycerine - it softens stains on wool.
Stain removers use chemicals to break down and wash away unwanted marks on our clothes. Different substances, like lemon juice or glycerine, are used depending on the type of fabric and the stain.
Teacher's Tip: Think of a stain remover as a "Targeted Solvent" that only attacks the dirt.
Exam Tip: Remember that Lemon juice works because of its "Citric Acid" content.

Objective Type Questions
Introduction to Chemistry

Question 1: Select the correct name from the choice A, B or C in each case.

1. The branch of Science which deals with the different forms of energy e.g. light and sound.
A : Chemistry
B : Physics
C : Biology
Answer: B : Physics

2. The branch of Chemistry which includes study of specific carbon compounds – built up of mainly carbon and hydrogen.
A : Inorganic Chemistry
B : Physical Chemistry
C : Organic Chemistry
Answer: C : Organic Chemistry

3. The scientist who formulated the Periodic Table.
A : John Dalton
B : Daniel Rutherford
C : Demitri Mendeleev
Answer: C : Demitri Mendeleev

4. Predecessors to the modern Chemist who created the ‘Philosoper’s stone’.
A : Botanists
B : Alchemists
C : Physicists
Answer: B : Alchemists

5. A synthetic fibre used in clothing.
A : Cotton
B : Jute
C : Terylene
Answer: C : Terylene

6. A medicine to treat pain, fever & inflammation.
A : Anaesthetic
B : Aspirin
C : Antacid
Answer: B : Aspirin

7. A water soluble cleaning agent – not inactivated by hard water.
A : Soap
B : Detergent
C : Cleanser
Answer: B : Detergent

8. A substance which absorbs moisture and keeps the skin dry and free from rashes.
A : Talc
B : Preservative
C : Emulsifier
Answer: A : Talc

9. A chemical used as a preservative for jams, pickles etc.
A : Titanium dioxide
B : Rayon
C : Benzoic acid
Answer: C : Benzoic acid

10. A substance which dissolves grease & oil and is preferred as a – drain cleaner.
A : Glycerine
B : Sodium hydroxide
C : Hydrogen peroxide
Answer: B : Sodium hydroxide

Question 2: Match the apparatus A to J shown below with their correct names 1 to 10 given below :
1. Delivery Tube — G
2. Pipette — H
3. Wire gauze — B
4. Bee-hive shelf — D
5. Thistle funnel — J
6. Flat bottom flask — I
7. Test tube stand — A
8. Burette — E
9. Retort — F
10.Conical flask — C

Question 3: Choose the correct answer for the following descriptions :

1. For gas preparations where heating is required.
(A) Flat bottom flask
(B) Retort
(C) Round bottom flask
Answer: (C) Round bottom flask

2. For holding washed test tubes.
(A) Test tube holder
(B) Test tube stand
(C) Retort stand
Answer: (B) Test tube stand

3. A glass apparatus resistant to chemicals, made of pyrex and used for heating specific liquids.
(A) Beaker
(B) Retort
(C) Boiling Tube
Answer: (C) Boiling Tube

4. A metallic apparatus which supports the wire gauze.
(A) A Tripod stand
(B) Retort stand
(C) Test tube stand
Answer: (A) A Tripod stand

5. A long glass apparatus closed at one end used for collecting gases.
(A) Measuring cylinder
(B) Gas jar
(C) Beehive shelf
Answer: (B) Gas jar

6. A glass apparatus which measures liquid by sucking the liquid at one end upto the marked level and later pouring it out.
(A) Burette
(B) Measuring cylinder
(C) Pipette
Answer: (C) Pipette

7. A long glass tube with a broad inlet at the top, which allows entry of the reactants into the round bottom flask, during laboratory preparations of gases.
(A) Thistle funnel
(B) Delivery tube
(C) Funnel.
Answer: (A) Thistle funnel

8. A clay vessel kept in a trough of water during collection of a gas by downward displacement of water.
(A) Retort
(B) Beehive shelf
(C) Burette
Answer: (B) Beehive shelf

9. A modern apparatus with an air regulator, used for heating purposes.
(A) Spirit lamp
(B) Bunsen burner
(C) Electric stove
Answer: (B) Bunsen burner

10. A rectangular mesh with an asbestos at its centre, kept for initiating even distribution of heat to the bottom of the apparatus.
(A) Tripod stand
(B) Wire gauze
(C) Retort stand
Answer: (B) Wire gauze

Question 4: Give reasons for the following :

Question 1: Alchemy was considered a pseudoscience.

Answer:
Towards the end of the 17th Century the scientific processes involving modem Chemistry started paving paths and Alchemy today is considered a pseudoscience and Chemistry regains its rightful position as a serious scientific field.
Alchemy was called a pseudoscience because it mixed magical beliefs with real science and didn't have clear, tested rules. Modern chemistry replaced it by using careful measurements and proven experiments to find facts about matter.
Teacher's Tip: Pseudoscience means it "looks" like science but isn't based on 100% facts.
Exam Tip: Use the timeline "end of the 17th Century" to show when chemistry became a formal science.

Question 2: Preservatives are added to food or beverages.

Answer:
Preservatives are added to food or beverages because of following reasons :
1. Prevent decomposition by bacteria or microbes.
2. Reduce risk of food borne infections.
3. Preserve nutritional quality of food.
Preservatives are essential because they stop germs from growing in our snacks and drinks. This ensures that the food stays healthy to eat and doesn't spoil quickly on the shelf.
Teacher's Tip: Think of preservatives as "Time-stoppers" for food spoilage.
Exam Tip: Always list "Preventing decomposition" as the primary reason for adding preservatives.

Question 3: Titanium dioxide is an important ingredient in cosmetics.

Answer:
It is a natural pigment powder which provides a base for mineral makeup. It provides mild sun protection and as a pigment gives a white colouration to coloured ingredients.
This chemical is used in makeup because it creates a solid white base and reflects sunlight. It helps protect the skin from UV rays while helping other colors in cosmetics show up brightly.
Teacher's Tip: Titanium dioxide is like a "Sun-shield" in your creams and makeup.
Exam Tip: Mention "sun protection" to explain why this chemical is so valued in skincare products.

Question 4: Aspirin is one of the most widely used medication – globally.

Answer:
Aspirin is one of the most widely used medication – globally because of following reasons :
1. It is a medicine to treat pain, fever & inflammation.
2. Aspirin given shortly after a heart attack, may decrease risk of death.
3. As long term use it may reduce, blood clots in people who are at a high risk.
Aspirin is popular because it can do many things, from stopping a headache to helping people during a heart attack. It is cheap, effective, and works quickly to reduce inflammation throughout the body.
Teacher's Tip: Aspirin is a "Multi-tasking" medicine.
Exam Tip: Mention its role in "heart attack" scenarios to show why it is used worldwide.

Question 5: Ordinary soap is wasted in hard water.

Answer:
Ordinary soap is wasted in hard water because hard water is one which does not lather with soap.
Hard water contains minerals that react with soap to create a sticky solid instead of bubbles. This means you have to use a lot more soap just to get a little bit of cleaning done.
Teacher's Tip: Hard water "kills" the bubbles in soap!
Exam Tip: Use the term "lather" to describe the bubbles that soap creates.

Question 6: A philosopher’s stone is not exactly a stone.

Answer:
Philosopher’s stone in a legendary substance, capable of turning inexpensive metals like lead or mercury into – gold and silver. (It was not literally a stone, but a powder or potion).
Even though it is called a "stone," alchemists often described it as a mysterious powder or liquid. They believed that just a small amount of this substance could magically transform any cheap metal into expensive gold.
Teacher's Tip: Remember it as a "Magic Ingredient" rather than a rock.
Exam Tip: Clarify that it is a "legendary substance" to show it isn't real.

Question 7: Food processing is an important procedure for obtaining marketable food products.

Answer:
Food processing – involves physical or chemical processes, to transform or change the raw ingredients in food into easy usable forms of food available in markets. Raw materials in food to Marketable food products.
Food Processing processes:
1. Mincing, Cooking, Pickling
2. Preservative addition, Canning, Packaging
Processing is what turns raw crops from a farm into the convenient food we find in supermarkets. It involves steps like cooking and packaging that make food safe to transport and easy for us to eat.
Teacher's Tip: Think of food processing as the "Factory journey" of a raw tomato into a bottle of ketchup.
Exam Tip: List "Canning" or "Packaging" as examples of processing steps.

Question 8: Cosmetics may contain preservatives, as one of their ingredients.

Answer:
They extend the shelf life of a cosmetic and may prevent growth of microorganisms.
Just like food, lotions and creams can go bad if bacteria start growing inside them. Adding preservatives ensures that your favorite cosmetic stays fresh and safe for your skin for many months.
Teacher's Tip: Preservatives are "Germ-fighters" in your makeup bottle.
Exam Tip: Mention "shelf life" as the main benefit of adding preservatives to products.

Question 9: Polyester is added to natural fibre cotton, to give terylene.

Answer:
Polyester is added to natural fibre cotton, to give terylene because this combination makes the fabric easy to clean and crease resistant.
By mixing cotton with polyester, we get a fabric that has the softness of cotton and the strength of plastic. This "Terylene" doesn't need much ironing and stays looking new for a long time.
Teacher's Tip: Terylene is a "Smart Fabric" because it doesn't wrinkle!
Exam Tip: Focus on "crease resistance" when explaining the benefits of this fiber blend.

Question 10: All medicines must be taken under proper doctors supervision and in the correct dose.

Answer:
All medicines must be taken under proper doctors supervision and in the correct dose because some medicine has side effect as aspirin not taken in proper dose may cause stomach ulcers similarly paracetamol if taken in high dose may cause liver problems.
Taking too much medicine or the wrong kind can harm your organs instead of healing your body. Doctors know exactly how much your body needs to fight a disease without causing dangerous side effects.
Teacher's Tip: A dose is like a key; it only works if it's the exact right size!
Exam Tip: Use "stomach ulcers" and "liver problems" as specific examples of what can happen with a wrong dose.