Maharashtra Board Class 8 Science Chapter 17 Man made Materials Solutions

Std 8 Science Chapter 17 Man-Made Materials Question Answer Maharashtra Board

Class 8 Science Chapter 17 Man-Made Materials Question Answer Maharashtra Board

1. Try To Find It:

Question a.Plastic shows ............ property, hence it can be moulded to any shape.
Answer: Plastic shows plasticity property, hence it can be moulded to any shape.
In simple words: Plasticity is the property that allows a material to be easily shaped or molded.

🎯 Exam Tip: Understanding key material properties like plasticity is crucial for explaining their uses.

 

Question b.Motor cars are coated with .......... .
Answer: Motor cars are coated with Teflon.
In simple words: Teflon is used as a coating on motor cars to protect them and give them a smooth finish.

🎯 Exam Tip: Knowing specific applications of man-made materials is important for practical understanding.

 

Question c.Thermocol melts at .......... °C.
Answer: Thermocol melts at more than 100 °C (it is about 240 °C).
In simple words: Thermocol, a type of plastic, starts melting at temperatures above 100°C, typically around 240°C.

🎯 Exam Tip: Remember the melting points or temperature sensitivities of common materials like thermocol.

 

Question d........... glass dissolves in water.
Answer: Alkali silicate or water glass dissolves in water.
In simple words: Alkali silicate glass, also known as water glass, is a type of glass that can dissolve in water.

🎯 Exam Tip: Distinguish between different types of glass and their unique properties, such as solubility.

2. Who Is My Partner?

Question a.

Column 'A'	Column 'B'
1. Lead glass	a. Plates
2. Bakelite	b. Mattresses
3. Thermocol	c. Electric bulb
4. Optic glass	d. Electric switch
5. Polypropylene	e. Lens

Answer:

Column 'A'	Column 'B'
1. Lead glass	c. Electric bulb
2. Bakelite	d. Electric switch
3. Thermocol	a. Plates
4. Optic glass	e. Lens
5. Polypropylene	b. Mattresses

In simple words: This matching exercise connects different types of man-made materials with their common uses or associated items.

🎯 Exam Tip: Familiarize yourself with the properties and applications of various man-made materials to accurately match them.

3. Answer The Following.

Question a.Thermocol is produced from which material?
Answer: Thermocol is made from polystyrene which is also a complex thermoplastic substance.
In simple words: Thermocol is made from polystyrene, which is a type of plastic that can be softened by heating.

🎯 Exam Tip: Remember the primary raw materials used for common man-made products.

 

Question b.Write uses of PVC.
Answer: PVC or Polyvinyl chloride is used for making bottles, raincoat, pipes, handbags, shoes, electric cable insulation, furniture, ropes, toys, etc.
In simple words: PVC is a versatile plastic used for many products like bottles, raincoats, pipes, and electrical insulation due to its durability.

🎯 Exam Tip: List multiple uses for common materials to demonstrate comprehensive knowledge.

 

Question c.Write the natural or man-made raw material of the following items.
Mattress, beaker, bangle, chair, gunny bag, broom, knife, pen.
Answer:

Items	Natural raw material	Man-made raw materials
Mattress	Cotton, Coir (Jute fibres)	Polypropylene
Beaker	-	Glass (Silicate or borosilicate glass)
Bangle	Gold, silver, lac, copper	Plastic, Glass
Chair	Wood	Plastic (PVC)
Gunny bag	Jute, cotton	Plastic (PVC)
Broom	Plant fibres	Plastic fibres (PVC)
Knife	Metals such as iron	Plastic
Pen	Metals	Plastic

In simple words: This table identifies whether common household items are primarily made from natural resources or synthetic (man-made) materials.

🎯 Exam Tip: Be able to classify materials as natural or man-made and provide examples of items made from each.

 

Question d.Which are the main ingredients of glass?
Answer: The main ingredients of glass are sand and silica.
In simple words: The primary components used to make glass are sand and silica.

🎯 Exam Tip: Know the fundamental ingredients of widely used man-made materials.

 

Question e.How the plastic is produced?
Answer:1. Plastics are derived from natural materials such as natural gas, oil, coal, minerals and plants. 2. The first synthetic plastics were i derived from cellulose, a substance found in plants and trees. This cellulose was heated with chemicals and resulted in a plastic like material. 3. In modern times, the different raw materials are used for making plastics, but most plastics are made from the hydrocarbons present in the natural gas, oil and coal. 4. Plastics are simply chains of like molecules linked together. These chains are called polymers. Thus, many plastics begin with "poly," such as polyethylene, polystyrene and polypropylene. 5. These polymers are made of carbon and hydrogen and sometimes oxygen, nitrogen, sulphur, chlorine, fluorine, phosphorous or silicon. 6. Plastic is produced in factories by suitable chemical reactions.
In simple words: Plastics are generally made from natural resources like oil and gas, which are then processed through chemical reactions to form long chains of molecules called polymers.

🎯 Exam Tip: Understand that plastics are synthetic polymers derived from various natural raw materials through chemical processes.

4. Distinguish Between.

Question a.Man-made material and natural material
Answer:

Man-made material	Natural material
1. The man-made materials are obtained from processes in scientific laboratory.	1. Natural materials are obtained from nature.
2. Man-made materials are subjected to rigorous processing to alter the material for serving the intended purpose.	2. Natural materials are subjected to less treatment and processing.
3. Man-made materials are typically much more durable having a very long lifespan.	3. Natural materials have shorter lifespan, because these materials were once alive and so gradually perish over time.
4. Maintaining man-made materials require less care and attention.	4. Maintaining natural materials requires lots of care and continuous attention.
5. Man-made materials can have a negative environmental impact because they are not sustainable. E.g. Glass, plastic, Thermocol, soil, metals, rubber.	5. Natural materials do not have a negative environmental impact because they can be degraded easily. E.g. Cotton, silk, wood.

In simple words: Man-made materials are synthetically created in labs, are often durable but can harm the environment, while natural materials come from nature, have shorter lifespans, and degrade more easily.

🎯 Exam Tip: Focus on origin, processing, durability, and environmental impact when differentiating between man-made and natural materials.

 

Question b.Thermoplastic and Thermosetting plastic:
Answer:

Thermoplastic	Thermosetting plastic
1. The plastic that can be moulded as per our wish is called thermoplastic.	1. The plastic in which a specific shape is given with the help of mould and this shape cannot be changed again on heating is called thermosetting plastic.
2. Thermoplastic substances can be recycled and reused. E.g. PVC - Polyvinyl chloride, PS - Polystyrene, PE - Polyethylene and PP - Polypropylene are types of thermoplastics.	2. Thermosetting plastic cannot be reused again. E.g. Bakelite, Melamine, Polyurethane and polyster are the types of thermosetting plastics.

In simple words: Thermoplastics can be repeatedly melted and reshaped, making them recyclable, while thermosetting plastics set into a permanent shape after initial heating and cannot be remelted.

🎯 Exam Tip: The key difference lies in their behavior when heated - thermoplastics soften, thermosetting plastics remain rigid. Provide examples for both categories.

5. Answer The Following In Your Own Words.

Question a.Explain the effect of following materials on environment and human health.
1. Plastic
2. Glass.
3. Thermocol.
Answer:
1. Plastic:
1. Plastic is non-degradable substance. Hence if thrown in any ecosystem, it remains unchanged for many years.
2. It is one of the worst environmental pollutants as its disposal is a major problem.
3. If thrown in water bodies, it affects the aquatic animals. Many of turtles mistake it for algae and eat the plastic. Eventually such animals die due to choking.
4. In terrestrial environment, the grazing animals like cattle are affected due to plastic.
5. If burnt it emits very toxic gases.
6. In landfill sites, it remains unchanged for thousands of years.
2. Glass:
1. The glass production is carried out at high temperatures of about 1500 °C. This burning emits many hazardous gases like sulphur dioxide, nitrogen dioxide, carbon dioxide. These gases cause the greenhouse effect.
2. Moreover, glass being non-degradable, cause pollution.
3. If broken glass pieces or any waste glass material is disposed into aquatic environment, it affects animals and plants.
4. Similarly, glass pieces block the drainages.
5. The waste glass thrown anywhere cause injury to terrestrial fauna.
3. Thermocol:
1. Thermocol contains carcinogenic ingredients in the form of styrene. If there is prolonged contact with thermocol, there is a possibility of blood cancer like leukemia and lymphoma.
2. Thermocol is non-degradable. It cannot be degraded into harmless substances easily.
3. If it is burnt for destruction, it releases toxic gases in atmosphere.
4. The plates and cups used for food, water, tea, etc. are made up of thermocol. This may affect the health. Reheating the food kept in thermocol releases styrene. This styrene may dissolve in that food, causing health problems like cancer.
In simple words: Plastic, glass, and thermocol are non-degradable materials that cause significant environmental pollution and can harm both wildlife and human health through various means like choking, toxic emissions, and disease-causing chemicals.

🎯 Exam Tip: When discussing environmental and health impacts, provide specific examples for each material and link them to non-biodegradability, toxicity, or physical harm.

 

Question b.Which measures will you arrange to minimize the environmental problems arising due to non-degradable plastic?
Answer:1. The use of plastic should be minimum. Reducing the consumption, reusing the same plastic again and again, recycling the used plastic and making some new products from the used plastic are some of the measures that can be adopted. 2. There are attempts to use plastic in making roads. Therefore, plastic is bought with good price at some places. 3. Therefore, instead of disposing of it anywhere, it should be collected and sold in best possible way. 4. The better alternatives for plastic should be adopted. 5. The awareness programmes about misuse of plastic should be arranged so that common man can understand the dangers of using plastic.
In simple words: To minimize plastic pollution, we should reduce, reuse, and recycle plastic, find alternative materials, encourage proper disposal, and raise public awareness about its dangers.

🎯 Exam Tip: Provide a comprehensive set of practical and educational measures when discussing solutions to environmental problems like plastic pollution.

6. Write Short Notes.

Question a.Glass production:
Answer: The general preparation of the glass is as follows: 1. Mixture of sand, soda, lime and small quantity of magnesium oxide is heated in furnace. 2. At 1700 °C sand or silicon dioxide melts. 3. To make the mixture melt at lesser temperature, pieces of discarded glasses are added to it. 4. This addition makes the mixture to melt at lesser temperature of 850 °C. 5. When all the ingredients of mixture are liquified, then again it is heated up to 1500 °C. 6. This heating is immediately followed by cooling. 7. The sudden cooling causes the mixture to become homogeneous, amorphous and transparent instead of crystalline. 8. For variety of glass types, different proportions of ingredients are used for heating.
In simple words: Glass is made by melting a mixture of sand, soda, lime, and other oxides at high temperatures, then rapidly cooling the liquid to form a transparent, amorphous solid.

🎯 Exam Tip: Outline the key steps and temperatures involved in glass production, emphasizing the role of rapid cooling for its amorphous structure.

 

Question b.Optic glass:
Answer:1. Optic glass or optical glass needs to be very clear and transparent as it is used in spectacles, lenses and other devices like microscopes. 2. Optic glasses are produced from the mixture of sand, soda, limestone, barium oxide and boron.
In simple words: Optic glass, used in lenses and optical instruments, is manufactured from a precise mixture of sand, soda, limestone, barium oxide, and boron to ensure high clarity and transparency.

🎯 Exam Tip: Highlight the specific properties required for optic glass (clarity, transparency) and relate them to its specialized composition.

 

Question c.Uses of plastic:
Answer: Plastic, the man-made material is used in various forms in modern age. According to the type of plastic, its uses are different.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र विभिन्न प्रकार के थर्मोप्लास्टिक सामग्रियों से बने लेखों को दर्शाता है, जिनमें बोतलें, पाइप, गियर, कंटेनर और अन्य घरेलू एवं औद्योगिक उपयोग की वस्तुएँ शामिल हैं। यह विभिन्न आकारों और उपयोगों में थर्मोप्लास्टिक की बहुमुखी प्रतिभा को प्रदर्शित करता है।
Thermoplastic
I. Thermoplastic materials are used for manufacturing following articles:
1. Polyvinyl chloride or PVC is used to make bottles, raincoat, pipes, handbags, shoes, electric cable insulation, furniture, ropes, toys, etc.
2. Polystyrene is used in making thermo insulating parts of electric appliances like refrigerators, gears of machines, toys, protective coverings like covers of CD and DVD, etc.
3. Polyethylene (PE) plastics are used for making milk bags, packing bags, flexible garden pipes, etc.
4. Polypropylene (PP) is used in making parts of loudspeakers and vehicles, ropes, mattresses, laboratory appliances, etc.
II. Thermosetting plastic is used in the manufacturing of the following items:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र थर्मोसेटिंग प्लास्टिक से निर्मित विभिन्न वस्तुओं को दर्शाता है, जैसे कि बिजली के स्विच, उपकरण हैंडल, और विभिन्न इलेक्ट्रॉनिक घटकों के आवरण। यह थर्मोसेटिंग प्लास्टिक के कठोर और गर्मी-प्रतिरोधी अनुप्रयोगों को दिखाता है।
Thermosetting plastic
1. Bakelite for making cabinets of radio, T.V., telephones, electric switches, toys, plastic handles of cookers, etc.
2. Melamine for making domestically useful items like cup - saucers, plates, tray, some spare parts of airplane engines, electric and sound insulating coverings, etc.
3. Polyurethane in making surfing boards, small boats, furniture, seats in vehicles, etc.
4. Polyester in fibreglass, toners of laser printers, textile industry, etc.
In simple words: Plastics are widely used in modern life, with thermoplastics forming items like bottles and pipes, and thermosetting plastics used for durable products such as electrical switches and appliance handles.

🎯 Exam Tip: Categorize plastic uses based on thermoplastic and thermosetting properties, providing distinct examples for each type.

Can You Tell?

Question 1.Make a list of 20 different man-made materials present in your home, school and places around and discuss.
Answer: Schoolbag, books, computer, table lamp, tube lights, benches, shoes, dress, pencil, pen, tiffin box, water bottle, raincoat, umbrella, medicine tablets, pen drive, chalk, duster, utensils, gas burner, biscuits.
In simple words: Many everyday items around us, like school supplies, electronic gadgets, clothing, and household goods, are made from various man-made materials.

🎯 Exam Tip: Provide a diverse list of items from different categories to show a broad understanding of man-made materials in daily life.

Can You Recall?

Question 1.How many plastic carry bags are brought in your home in a day? What happens to those later on?
Answer: Till May 2018 about one or two plastic bags were brought in our home every day. But now due to prohibition on plastic bags and other plastic items by the Government, the use of plastic has been drastically reduced. The bags brought at home caused lot of plastic pollution. Plastic is non-biodegradable, thus it always created problem of their disposal. If dumped in a water body, it can be hazardous for aquatic animals. If thrown in the garbage, plastic articles find their way to landfilling areas. If thrown anyhow plastic may be consumed by stray animals. This causes toxic effects on them. If burnt they emit toxic gases.
In simple words: The number of plastic bags used daily has decreased due to government bans, but they still pose a disposal challenge as they are non-biodegradable and harmful to the environment and animals if discarded improperly or burnt.

🎯 Exam Tip: Discuss the impact of government policies, the non-biodegradable nature of plastic, and its multiple negative effects on ecosystems and health.

 

Question 2.How are the used up and thrown away carry bags, water bottles, milk bags recycled?
Answer: The plastic waste is collected by the kabadiwala or sweepers. They sell these articles to the recycling units. In recycling units, the recycling of some of the plastic items is done. This leads to formation of plastic of low quality which may be used in making some newer plastic items.
In simple words: Used plastic items are collected by waste handlers and sent to recycling units, where they are processed into lower-quality plastic for new products.

🎯 Exam Tip: Describe the basic steps of plastic recycling, including collection and conversion into new items, noting that quality may decrease.

 

Question 3.Which material is wrapped around the items of glass or similar material during transport to prevent from breaking up?
Answer: The plastic bubble wrap or thermocol is used to protect fragile items from the shocks and breaks during their transport.
In simple words: Fragile items like glass are cushioned with plastic bubble wrap or thermocol during transport to prevent breakage from shocks.

🎯 Exam Tip: Identify common packaging materials and their function in protecting delicate goods.

Project:

Question 1.Collect the information about the plastic used in production of utensils used in microwave oven.
Answer: Students are advised to collect the information about the plastic used in the production of utensils used in microwave oven.
In simple words: This project asks students to research specific types of plastics suitable for microwave use, considering their heat resistance and safety properties.

🎯 Exam Tip: For project-based questions, describe the scope of the project and what key information students should focus on gathering.

 

Question 2.Collect the information about the material used in production of denture. (A set of artificial teeth)
Answer: Students are advised to collect the information about the material used in production of denture.
In simple words: This project requires students to investigate the materials used to create artificial teeth (dentures), focusing on their properties, biocompatibility, and manufacturing.

🎯 Exam Tip: When handling research-based projects, encourage students to explore the materials' properties, applications, and any relevant scientific principles.

Class 8 Science Chapter 17 Man-Made Materials Important Questions And Answers

Try To Find It:

Question 1.The plastic that can be moulded as per our wish is called .......... .
Answer: The plastic that can be moulded as per our wish is called thermoplastic.
In simple words: Thermoplastic is the type of plastic that can be softened by heating and then reshaped as desired.

🎯 Exam Tip: Understand and differentiate between thermoplastic and thermosetting plastic based on their re-molding capabilities.

 

Question 2........... is a type of plastic used for manufacturing artificial teeth.
Answer: Polyacrylic is a type of plastic used for manufacturing artificial teeth.
In simple words: Polyacrylic is a specific type of plastic commonly used in making artificial teeth due to its suitable properties.

🎯 Exam Tip: Identify specific polymers used for particular applications, especially in medical or specialized fields.

 

Question 3.Thermocol is a form of a complex material called .......... .
Answer: Thermocol is a form of a complex material called polystyrene.
In simple words: Thermocol is essentially a foamed version of polystyrene, a complex plastic material.

🎯 Exam Tip: Connect common product names (like Thermocol) with their scientific material names (polystyrene).

Write Whether The Following Statements Are True Or False: Rewrite The False Statements After Correcting:

Question 1.Plastics are inorganic polymers that show plasticity.
Answer: False. (Plastics are organic polymers that show plasticity.)
In simple words: Plastics are actually organic polymers, meaning they are carbon-based compounds, and they exhibit plasticity, which is the ability to be molded.

🎯 Exam Tip: Distinguish between organic and inorganic compounds, and understand that most plastics are organic polymers.

 

Question 2.Polythene, PVC are thermosetting plastic materials.
Answer: False. (Polythene, PVC are thermoplastic materials.)
In simple words: Polythene and PVC are types of thermoplastics, meaning they can be melted and reshaped, unlike thermosetting plastics which set permanently.

🎯 Exam Tip: Correctly classify common plastics (Polythene, PVC) as either thermoplastic or thermosetting.

 

Question 3.Plastic is bad conductor of heat and electricity.
Answer: True.
In simple words: Plastic does not conduct heat or electricity well, making it an effective insulator.

🎯 Exam Tip: Recall the insulating properties of plastic, which is why it's used in electrical wiring and handles.

 

Question 4.Surfing boards are made up of bakelite.
Answer: False. (Surfing boards are made up of polyurethane.)
In simple words: Surfing boards are typically made from polyurethane, a lightweight and durable material, not bakelite.

🎯 Exam Tip: Be aware of the specific materials used for various products, especially those requiring particular properties like buoyancy or strength.

 

Question 5.Being bad conductor of electricity, glass is used as insulator in electric appliances.
Answer: True.
In simple words: Glass is a poor conductor of electricity, hence it is utilized as an insulating material in various electrical appliances.

🎯 Exam Tip: Understand the electrical conductivity properties of different materials and their applications as conductors or insulators.

Match The Columns:

Question 1.

Column A	Column B
1. Borosilicate glass	a. Oxide of specific metal.
2. Alkali silicate glass	b. Sand, soda, limestone, barium oxide and boron.
3. Lead glass	c. Sand and soda.
4. Optical glass	d. Sand, soda, limestone and lead oxide.
5. Coloured glass	e. Sand, soda, boric acid and aluminium oxide.

Answer:

Column A	Column B
1. Borosilicate glass	e. Sand, soda, boric acid and aluminium oxide.
2. Alkali silicate glass	c. Sand and soda.
3. Lead glass	d. Sand, soda, limestone and lead oxide.
4. Optical glass	b. Sand, soda, limestone, barium oxide and boron.
5. Coloured glass	a. Oxide of specific metal.

In simple words: This exercise matches different types of glass with their specific chemical compositions, highlighting the varying ingredients used to achieve distinct properties.

🎯 Exam Tip: Learn the primary components of various specialized glasses and how these compositions relate to their unique characteristics and uses.

Find The Odd One Out:

Question 1.Bakelite, Melamine, Polystyrene, Polyester.
Answer: Polystyrene (All others are thermosetting plastic materials, polystyrene is thermoplastic.)
In simple words: Polystyrene is the odd one out because it is a thermoplastic, meaning it can be melted and reshaped, whereas Bakelite, Melamine, and Polyester are thermosetting plastics that cannot be reshaped after initial curing.

🎯 Exam Tip: Understand the fundamental difference between thermoplastics and thermosetting plastics to correctly identify exceptions in a list.

 

Question 2. Polyvinyl chloride, Polystyrene, Polypropylene, Polyurethane.
Answer: Polyurethane (All others are thermoplastic materials, polyurethane is thermosetting plastic.)
In simple words: Polyurethane is the odd one out because it's a thermosetting plastic, while the others listed are all thermoplastics.

🎯 Exam Tip: Understanding the difference between thermoplastic and thermosetting plastic is crucial for classifying materials correctly in exams.

 

Question 3. Vegetable peels, Cotton bolls, Wooden scraps, Plastic bag.
Answer: Plastic bag (All others are degradable materials, plastic is non-degradable.)
In simple words: The plastic bag is the odd one because it doesn't break down naturally, unlike vegetable peels, cotton bolls, and wooden scraps which are degradable.

🎯 Exam Tip: Knowing which materials are degradable and which are non-degradable is important for environmental awareness and related questions.

 

Question 4. Teflon, Polyacrylic, Fibreglass, Polyester.
Answer: Fibreglass (All others are types of plastic.)
In simple words: Fibreglass is the different one here because Teflon, Polyacrylic, and Polyester are all specific types of plastics, whereas fibreglass is a composite material made from glass fibers and resin.

🎯 Exam Tip: Be precise in distinguishing between specific plastic polymers and composite materials for accurate answers.

Considering The Relationship In The First Pair, Complete The Second Pair:

 

Question 1. Processed glass: Fen glass :: Alkali silicate glass : ..........
Answer: Water glass
In simple words: Fen glass is a type of processed glass, and water glass is another name for alkali silicate glass.

🎯 Exam Tip: Memorize common names and types of different glass compositions.

 

Question 2. Ferrous oxide: Bluish green glass : : Copper oxide : ........
Answer: Red glass
In simple words: Ferrous oxide gives glass a bluish-green color, and copper oxide is used to produce red-colored glass.

🎯 Exam Tip: Understand how different metal oxides are used as coloring agents in glass manufacturing.

 

Question 3. Lens: Optical glass :: Laboratory glassware : ..........
Answer: Silica glass
In simple words: Optical glass is used for lenses, and silica glass is commonly used for laboratory glassware due to its heat resistance and clarity.

🎯 Exam Tip: Connect specific applications with the types of glass best suited for them.

 

Question 4. Light bulbs, Tubes: Lead glass : : Medicine storing : .........
Answer: Borosilicate glass
In simple words: Lead glass is used in light bulbs and tubes, while borosilicate glass is preferred for storing medicines because of its chemical inertness and resistance to thermal shock.

🎯 Exam Tip: Relate the properties of different glass types to their specific uses in various industries.

 

Question 5. Glass: Mixture of silica and silicate :: Thermocol: ..........
Answer: Polystyrene.
In simple words: Glass is made from a mixture of silica and silicate, and similarly, thermocol is made from polystyrene.

🎯 Exam Tip: Remember the basic components or raw materials used to create common man-made materials.

Distinguish Between:

 

Question 1. Degradable and Non-degradable substances:
Answer:

Degradable substances	Non-degradable substances
1. The substances which can be naturally reduced into their inorganic constituents are called degradable substances.	1. The substances that cannot be degraded on their own into their inorganic constituents are called non-degradable substances.
2. Degradable substances are not accumulated in the nature.	2. Non-degradable substances remain accumulated in the nature for a long time.
3. Degradable substances emit foul odour when they are being decomposed.	3. Non-degradable substances may not emit foul odour as they are not degraded. But they make the place look dirty.
4. Usually microorganisms play a part in the degradation process, hence such substances are also called biodegradable.	4. Microorganisms cannot act on non-degradable substances and hence they are also called non-biodegradable substances.
E.g. Vegetables, fruits, wood, cotton or wool fibres, etc.	E.g. Plastic, thermocol, glass, metals, etc.

In simple words: Degradable substances break down naturally over time with the help of microorganisms, returning to nature without accumulation, while non-degradable substances do not break down easily and persist in the environment for very long periods, causing pollution.

🎯 Exam Tip: When distinguishing, provide clear definitions, differences in behavior (accumulation, decomposition), and relevant examples for each category.

Write Short Notes:

 

Question 1. Properties of plastic:
Answer:
1. Plastic is non-corrosive.
2. It is non-degradable as it does not decompose.
3. The factors such as humidity, heat, rain, etc. do not affect plastic.
4. Any coloured item can be manufactured from plastic.
5. Plastic shows property of plasticity. Thus it can be moulded into any shape that is needed.
6. Plastic is a bad conductor of heat and electricity.
7. Plastic is light-weight and thus preferred for carrying.
In simple words: Plastic is a versatile material that is non-corrosive, light-weight, and can be molded into various shapes. It is also a poor conductor of heat and electricity and does not decompose easily, making it durable but also an environmental concern.

🎯 Exam Tip: For short notes, list key properties clearly and concisely, explaining each point briefly.

 

Question 2. Properties of Glass:
Answer: The glass becomes soft on heating and thus can be moulded into desired shape.
1. According to ingredients added at the time of preparation of glass, its density changes accordingly.
2. Glass is slow conductor of heat. If a cold glass is quickly heated, it cracks suddenly. Similarly, the warm glass if exposed to sudden cooling, it too cracks.
3. Glass is a bad conductor of electricity. Therefore, it is used as insulating material in electric appliances.
4. Glass is transparent, allowing most of light to pass through it. If there are chromium, vanadium or iron oxides in the glass, large amount of light is absorbed in glass.
In simple words: Glass can be molded when hot, is generally transparent, and is a poor conductor of both heat and electricity. Its density and color can vary based on its composition and added ingredients.

🎯 Exam Tip: When describing properties, include both physical characteristics (transparency, moldability) and functional ones (conductivity, heat resistance).

Answer The Following Questions In One Sentence Only:

 

Question 1. What is the use of plastic in healthcare sector?
Answer: Saline bottles, pouches, blood bags, syringes and medicine bottles are made up of plastic, making plastic irreplaceable in the healthcare sector.
In simple words: Plastic is essential in healthcare for items like saline bottles, blood bags, syringes, and medicine containers.

🎯 Exam Tip: Focus on specific examples when answering questions about applications or uses.

 

Question 2. Which material is used in coating of vehicles? Why?
Answer: Teflon is used for coating the vehicle as it protects the vehicles from scratches.
In simple words: Teflon is used to coat vehicles because it provides a protective layer against scratches.

🎯 Exam Tip: When a "why" is asked, ensure your answer provides the reason or benefit of the material's use.

 

Question 3. What is the use of polyacrylic type of plastic?
Answer: Polyacrylic plastic used for manufacturing lenses and in the manufacture of artificial teeth.
In simple words: Polyacrylic plastic is utilized for making lenses and artificial teeth.

🎯 Exam Tip: Link specific plastic types to their primary applications.

 

Question 4. What is 4R principle?
Answer: The 4R principle is the way of behaviour that prevents or lessens the environmental pollution. The 4Rs are Reduce, Reuse, Recycle and Recover.
In simple words: The 4R principle is an environmental guideline focused on reducing pollution through Reduce, Reuse, Recycle, and Recover practices.

🎯 Exam Tip: Clearly state what the principle is and list all its components when asked.

 

Question 5. What are the eco-friendly options for a plastic bag?
Answer: Jute bag, cloth bag and reusable bags of any natural materials are the eco-friendly options for the plastic bag.
In simple words: Eco-friendly alternatives to plastic bags include jute bags, cloth bags, and reusable bags made from natural materials.

🎯 Exam Tip: Provide practical and common examples when asked for eco-friendly alternatives.

 

Question 6. How is Borosilicate glass produced?
Answer: Borosilicate glass is produced by melting the mixture of sand, soda, boric acid and aluminium oxide.
In simple words: Borosilicate glass is made by melting together sand, soda, boric acid, and aluminum oxide.

🎯 Exam Tip: For production questions, list the key raw materials involved in the manufacturing process.

 

Question 7. When is large amount of light absorbed in the glass?
Answer: If there are oxides of either chromium, vanadium or iron in the glass, large amount of light is absorbed in it.
In simple words: Glass absorbs a large amount of light when it contains oxides of chromium, vanadium, or iron, which act as coloring agents.

🎯 Exam Tip: Understand the role of impurities or additives in altering the optical properties of glass.

Give Scientific Reasons:

 

Question 1. It is harmful to eat food kept in thermocol.
Answer: Thermocol is made up from polystyrene. It is carcinogenic (cancer causing) substance. When food kept in thermocol containers is reheated, this, styrene dissolves in it. This may affect the health of the person who consumes such food. It has been noted that there is a great possibility of blood cancer like leukaemia and lymphoma if one remains in contact with thermocol for a longer time. Thus, it is harmful to eat food kept in thermocol.
In simple words: Eating food kept in thermocol is harmful because thermocol, made of polystyrene, can release styrene, a cancer-causing substance, especially when reheated, which can then leach into the food.

🎯 Exam Tip: When explaining scientific reasons, identify the core substance, its harmful properties, and the mechanism of harm.

 

Question 2. Vessels used to cook food in the microwave oven are made up of plastic.
Answer: The vessels made from metals cannot be used in the microwave oven. The microwaves cannot penetrate steel and so can only heat the contents through the open top. Some metals cause sparking with microwaves. Microwave energy is absorbed differently by different materials. Plastics of only certain kind are more suitable to be used in the microwave oven.
In simple words: Plastic vessels are used in microwave ovens because microwaves can pass through specific types of plastic to heat the food directly, unlike metal vessels which block microwaves or can cause dangerous sparking.

🎯 Exam Tip: Explain both why certain materials (metals) are unsuitable and why others (specific plastics) are preferred for microwave use, focusing on microwave interaction.

Answer The Following:

 

Question 1. What are the qualities of thermocol?
Answer:
1. Thermocol is modern man-made material made from polystyrene.
2. It can be transformed into liquid state when heated at more than 100 °C temperature. On cooling, it returns to the solid state.
3. Therefore, any desired shape can be given to it.
4. It acts as a good shock-absorber and hence used as a packing material to transport brittle material.
5. It is a bad insulator of heat and hence used for storing fish and other perishable articles in market.
In simple words: Thermocol, made of polystyrene, is a man-made material that can be melted and reshaped, acts as a good shock-absorber, and is a poor heat insulator, making it useful for packaging and insulation.

🎯 Exam Tip: List both the physical properties and the practical applications that stem from those qualities.

Think About It:

 

Question 1. Why are the plastic tanks used for storage of chemicals?
Answer: Plastic is non-corrosive. It is comparatively non-reactive and it does not decompose. Moreover, the plastic containers are easier for handling. They are lighter and unbreakable. Hence the plastic tanks are used for storage of chemicals.
In simple words: Plastic tanks are used to store chemicals because plastic is non-corrosive, non-reactive, light-weight, unbreakable, and doesn't decompose, offering safe and easy handling.

🎯 Exam Tip: Focus on the chemical inertness and physical durability of plastic as key reasons for its use in chemical storage.

 

Question 2. Why most of domestically useful items are replaced by plastic?
Answer: Plastic is lighter and unbreakable. The handling thus becomes easier. It is non-corrosive, hence pickles, spices, etc. can be stored in plastic containers. It is cheaper as compared to the metal and glass articles. Thus, it becomes popular with general public. It is easier to wash and maintain the plastic articles. These are some of the reasons of making plastic a domestically useful material.
In simple words: Many household items are now made of plastic because it is lighter, unbreakable, non-corrosive, cheaper, and easier to clean and maintain compared to metal or glass.

🎯 Exam Tip: When discussing material replacement, highlight the comparative advantages (cost, durability, maintenance) of the newer material.

Collect Information:

 

Question 1. To prevent the degradation due to sunlight, some materials are stored in which type of bottles?
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र विभिन्न प्रकार के कांच और कांच के बर्तनों को दर्शाता है। इसमें पारदर्शी, भूरे और नीले रंग की बोतलें और गिलास दिखाए गए हैं, जो दर्शाते हैं कि कांच को विभिन्न आकार और रंगों में ढाला जा सकता है और इसका उपयोग तरल पदार्थ या सामग्री रखने के लिए किया जाता है। The amber glass or brown coloured glass bottles are used to store the materials that may get degraded due to sunlight. This colour prevents the ultraviolet rays of the sun to enter the bottle and bring about chemical changes in the materials. Especially, for sensitive medicines, brown glass bottles are used.
In simple words: Materials sensitive to sunlight, especially medicines, are stored in amber or brown glass bottles because their color blocks harmful ultraviolet rays, preventing chemical degradation.

🎯 Exam Tip: Relate the color of the glass to its function in protecting contents from specific environmental factors like UV light.

 

Question 2. Which type of glass is used in vehicles to avoid injuries in accidents?
Answer: Front and rear doors have tempered glass. The windshield has laminated safety glass. Even if the accident takes place the glass pieces do not injure the passengers. Laminated safety glass combines two curved glass sheets and a plastic lamina between the two layers of the glass.
This glass is tough and protective. Tempered glass on the other hand is toughened glass which is processed by controlled thermal or chemical treatments. Upon breaking, the tempered glasses crumble into small granular chunks instead of splintering into sharp glass pieces. This prevents the injuries.
In simple words: Laminated safety glass is used for windshields, and tempered glass for other windows in vehicles. Laminated glass prevents shattering by holding fragments together with a plastic layer, while tempered glass breaks into small, blunt pieces, both designed to minimize injury during accidents.

🎯 Exam Tip: Differentiate between laminated safety glass and tempered glass, explaining how each contributes to safety in vehicles during an accident.

Sketch And Label The Diagram Of Glass Manufacturing Process:

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र कांच निर्माण प्रक्रिया को दर्शाता है। इसमें कच्चे माल को भट्ठी में पिघलाया जाता है, फिर पिघले हुए कांच को रोलर्स के माध्यम से एक पतली पट्टी के रूप में फैलाया जाता है, जिसे अंत में कटर द्वारा वांछित आकार में काटा जाता है। यह प्रक्रिया कच्चे माल से तैयार कांच पट्टी बनाने के चरणों को दर्शाती है।

Open-Ended Questions:

 

Question 1. Classify and make a chart of the materials used in various items in house. Make additions to that chart with reference to various materials.
Answer:

Name of the item	Material used
	Man-made	Natural
Wooden chair	Plastic	Wood
Comb	Plastic	Ivory, wooden
Pressure cooker	Alloys, plastic handle and rubber ring.	Metals
Notebooks and books	Bleaching agents, printing ink	Paper obtained from trees
Purses and bags	Plastic, rubber, polyester, alloys for zips and buttons	Leather, cotton, silk
Clothes	Polyester fabric	Cotton, silk, jute

In simple words: Household items are made from a combination of man-made and natural materials; for example, a wooden chair might have plastic parts, while a pressure cooker uses alloys and rubber along with metals.

🎯 Exam Tip: When creating classification charts, ensure that items are listed consistently under either "Man-made" or "Natural" categories for their primary or significant components.

 

Question 2. Make list about use of thermocol in your daily life.
Answer:
1. Decorative items used at the time of festivals.
2. Packing materials.
3. Insulating boxes to keep food warm.
4. Insulating boxes to keep fish in iced condition to prevent decomposition.
5. Thermocol beads in the bean bags.
In simple words: Thermocol is commonly used for festive decorations, packaging fragile items, making insulating boxes for food and ice, and as filler beads in bean bags due to its lightweight and insulating properties.

🎯 Exam Tip: Provide diverse examples that cover different applications of the material in everyday life.