RBSE Solutions Class 8 Science Chapter 3 Synthetic Fibres and Plastics

Synthetic Fibres and Plastics Textbook Questions Solved

I. Multiple Choice Questions

 

Question 1. The material used for making non stick utensils of kitchen is:
(a) PVC
(b) Polyether
(c) Teflon
(d) Rayon
Answer: (c) Teflon
In simple words: Teflon is a special plastic that makes surfaces non-stick and heat-resistant, perfect for cooking pots and pans. It helps food not stick to the pan when you cook.

🎯 Exam Tip: Remember Teflon's unique property of being non-stick and heat-resistant, which is key to its use in kitchenware.

 

Question 2. Which of the following group is of synthetic fibres?
(a) Nylon, Terelene, Rayon
(b) Compound
(c) Acrylic, Silk, Wool
(d) PVC, Polyether, Bakelite
Answer: (a) Nylon, Terelene, Rayon
In simple words: Synthetic fibres are man-made. Out of the choices, Nylon, Terelene (a type of polyester), and Rayon (which is chemically processed natural material) are all types of synthetic fibres.

🎯 Exam Tip: Know the common examples of synthetic fibres to easily identify them in options. Remember that Rayon is called a 'regenerated' fibre but grouped with synthetics.

 

Question 3. The handles of utensils are made from-
(a) Polyether
(b) Nylon
(c) PVC
(d) Bakelite
Answer: (d) Bakelite
In simple words: Bakelite is a thermosetting plastic. It does not get soft or melt when heated, making it ideal for utensil handles that get hot. This property prevents burns.

🎯 Exam Tip: For materials exposed to heat, think of thermosetting plastics like Bakelite because they are resistant to high temperatures and do not deform.

 

Question 4. Which is not the property of plastics ?
(a) Inert
(b) Durable
(c) Light weight
(d) Conduction of electricity
Answer: (d) Conduction of electricity
In simple words: Plastics are generally poor conductors of electricity, meaning they do not allow electricity to pass through easily. This makes them good insulators for wires. All other options like being inert, durable, and lightweight are true properties of plastics.

🎯 Exam Tip: Remember that plastics are excellent electrical insulators, which is a key property that distinguishes them from materials like metals.

 

Question 5. Thermoplastics is
(a) Bakelite
(b) Melamine
(c) Polyether
(d) None of these
Answer: (c) Polyether
In simple words: Thermoplastics are plastics that can be softened by heating and then reshaped. Bakelite and Melamine are thermosetting plastics, which means they do not soften upon heating. Polyether is a type of thermoplastic.

🎯 Exam Tip: Distinguish between thermoplastics (can be softened and remoulded) and thermosetting plastics (cannot be softened or remoulded after initial setting).

Fill in the blanks:

 

Question 1. Synthetic fibres are also called. ...........or fibres.
Answer: artificial, polymer
In simple words: Synthetic fibres are also known as artificial or polymer fibres. They are made by humans from chemical processes.

🎯 Exam Tip: Know the different names for synthetic fibres, such as artificial fibres or man-made fibres.

 

Question 2. Rayon is also called.
Answer: artificial silk
In simple words: Rayon is often called artificial silk because it looks and feels like silk but is made from natural materials that have been processed.

🎯 Exam Tip: Remember that Rayon mimics silk's appearance and texture, which is why it earned the name "artificial silk."

 

Question 3. The polymerisation of acetonitryl gives.
Answer: Orion
In simple words: When many acetonitrile molecules join together, they form a long chain called a polymer, and this specific polymer is known as Orion.

🎯 Exam Tip: Connect the specific monomer (acetonitrile) to its resulting polymer (Orion) formed through the polymerization process.

 

Question 4. Plastic is also a type of.
Answer: synthesised polymer
In simple words: Plastics are synthetic polymers, meaning they are large molecules made by chemically joining smaller repeating units.

🎯 Exam Tip: Understand that plastics are fundamentally polymers, which are large molecules made from many smaller units linked together.

Question 3. Match the column A with column B

 

Answer:

In simple words: This table matches different types of fibres and plastics with their common uses or properties. Rayon is an artificial fibre, Nylon is used for clothes, thermosetting plastics like Teflon can be a non-stick coating, and PVC is often used for pipes.

🎯 Exam Tip: Familiarize yourself with the specific applications and characteristics of each major type of synthetic fibre and plastic.

Synthetic Fibres and Plastics Short Answer Type Questions

 

Question 1. Why it is not advice to burn plastics and synthetic fibres?
Answer: It is not advised to burn plastics and synthetic fibres. This is because burning them needs a lot of energy. During this process, many poisonous gases are released into the air. These gases cause a lot of pollution in the environment, making it unhealthy to breathe. These harmful fumes can cause respiratory issues and environmental damage.
In simple words: Do not burn plastics or synthetic fibres because they release harmful, poisonous gases into the air and cause a lot of pollution.

🎯 Exam Tip: Highlight the release of poisonous gases and environmental pollution as the main reasons for not burning plastics and synthetic fibres.

 

Question 2. What are thermoplastics? Explain with example.
Answer: Thermoplastics are a type of plastic that become soft and can change shape easily when heated. Once they cool down, they become hard again. The good thing about thermoplastics is that they can be melted and recycled many times. A common example is polythene, which is used to make plastic bags and bottles. Another example is PVC (polyvinyl chloride), used for pipes and window frames. This property allows for reuse and remoulding, making them versatile materials.
In simple words: Thermoplastics are plastics that get soft when hot and can be reshaped. They can be recycled. Polythene and PVC are examples.

🎯 Exam Tip: Clearly define thermoplastics by their ability to soften on heating and be recycled, providing common examples like polythene and PVC.

 

Question 3. Terrycot is obtained by mixing two types of fibres? Name these fibres.
Answer: Terrycot is made by mixing two different types of fibres. These fibres are terylene and cotton. Terylene is a synthetic polyester fibre, while cotton is a natural fibre from plants. Combining them creates a fabric that is strong and comfortable.
In simple words: Terrycot is a blend of terylene (a synthetic fibre) and cotton (a natural fibre).

🎯 Exam Tip: Remember that "terrycot" combines "tery" from terylene and "cot" from cotton, indicating its mixed composition.

 

Question 4. What is non-biodegradable substances?
Answer: Non-biodegradable substances are materials that do not break down naturally in the environment, or they take a very, very long time to decompose. This happens because micro-organisms like bacteria and fungi cannot break them down. Examples include all kinds of plastics, artificial fibres, and metal cans. These materials often stay in landfills for hundreds of years.
In simple words: Non-biodegradable substances are materials that do not break down naturally in the environment, such as plastics, artificial fibres, and metal cans.

🎯 Exam Tip: Define non-biodegradable by stating they do not decompose naturally and provide clear examples like plastics and metal cans.

 

Question 5. What is polymerisation?
Answer: Polymerisation is a process where many small, simple molecules, called monomers, link together to form a very large, complex molecule called a polymer. It is like building a long chain by joining many identical beads. This process is how synthetic fibres and plastics are created.
In simple words: Polymerisation is the process where small units (monomers) join to form a big chain (polymer).

🎯 Exam Tip: Explain polymerisation using the terms "monomer" (small unit) and "polymer" (large chain) to clearly describe the process.

 

Question 2. Explain the statement “do not use plastics in daily life as far as possible”.
Answer: Using many synthetic polymers, like plastics, has caused certain environmental problems. While plastic is a useful material due to its properties, it also has a negative side. Here are the reasons why we should avoid using plastics as much as possible:
1. Plastics cause health problems and harm the environment because they do not break down naturally and cannot be decomposed by tiny living things (micro-organisms).
2. They stop rainwater from soaking into the ground, which affects how plants grow.
3. Plastics left on roadsides or floating in water bodies create places for germs to grow and can make animals sick if they eat them.
4. When plastics are in water, they can be toxic to sea life.
5. Burning plastics releases harmful gases that pollute the air.
6. Plastics take many years to break down.
To help avoid these problems, we should:
7. Recycle plastics by collecting, sorting, and processing them again.
8. Follow the 4R principle: reduce, reuse, recycle, and recover.
9. Use cotton or jute bags for shopping instead of plastic bags.
10. Separate garbage into things that break down naturally (biodegradable) and things that don't (non-biodegradable), and recycle the non-biodegradable waste.
In simple words: Plastics harm the environment because they don't break down, pollute air and water, and hurt animals. We should use less plastic and focus on recycling, reducing, reusing, and recovering materials.

🎯 Exam Tip: Emphasize the non-biodegradable nature of plastics, their pollution effects, and the 4R principle as solutions.

Synthetic Fibres and Plastics Additional Questions Solved

I. Multiple Choice Questions

 

Question 1. The fibre obtained by processing cellulose is called
(a) Rayon
(b) Nylon
(c) Polystyrene
(d) Terylene
Answer: (a) Rayon
In simple words: Rayon is a fibre made by chemically treating cellulose, which comes from wood pulp or cotton. It is considered a regenerated fibre because it starts from a natural polymer.

🎯 Exam Tip: Link Rayon directly to its origin from processed cellulose to ensure accuracy.

 

Question 2. This is the synthetic fibre
(a) Wool
(b) Acrylic
(c) Cotton
(d) Polystyrene.
Answer: (b) Acrylic
In simple words: Synthetic fibres are man-made. Among the choices, wool and cotton are natural fibres. Polystyrene is a plastic, not typically a fibre. Acrylic is a synthetic fibre often used as a wool substitute.

🎯 Exam Tip: Clearly differentiate between natural fibres (wool, cotton) and synthetic fibres (acrylic, nylon, polyester).

 

Question 3. The fibre obtained by the chemical treatment of wood pulp is called:
(a) Rayon
(b) Silk
(c) Cotton
(d) Polyester
Answer: (a) Rayon
In simple words: Rayon is made from wood pulp, which is treated with chemicals. Silk and cotton are natural fibres, and polyester is a fully synthetic fibre made from petroleum.

🎯 Exam Tip: Recognize Rayon's unique status as a semi-synthetic fibre, produced from natural raw materials (wood pulp/cellulose) through chemical processing.

 

Question 5. Polyester is a polymer of
(a) Ester
(a) Ethane
(c) Ethylene
(d) Methane
Answer: (a) Ester
In simple words: Polyester is a type of polymer that is formed from many ester units linked together. Esters are specific chemical compounds.

🎯 Exam Tip: Understand that the "ester" linkage is fundamental to the structure of polyester fibres.

 

Question 6. The smallest unit of polymer is called
(a) Cell
(b) Atom
(c) Monomer
(d) Plastic
Answer: (c) Monomer
In simple words: Polymers are large chains made from repeating smaller units, and each one of these small, repeating units is called a monomer.

🎯 Exam Tip: Remember the core definition: polymers are long chains, and monomers are their individual building blocks.

 

Question 7. The thermosetting plastic is
(a) PVC
(b) Bakelite
(c) Teflon
(d) Nylon
Answer: (b) Bakelite
In simple words: Thermosetting plastics, like Bakelite, cannot be softened or remoulded once they are heated and set into a shape. PVC, Teflon, and Nylon are thermoplastics.

🎯 Exam Tip: Always distinguish thermosetting plastics (Bakelite, Melamine) from thermoplastics (PVC, Teflon, Nylon) based on their heat response.

 

Question 8. Which of the following is not a thermoplastic?
(a) PVC
(b) Polythene
(c) Melamine
(d) Teflon
Answer: (c) Melamine
In simple words: Thermoplastics can be melted and reshaped multiple times. Melamine is a thermosetting plastic, meaning it sets permanently after heating and cannot be remoulded. PVC, Polythene, and Teflon are all thermoplastics.

🎯 Exam Tip: Identify thermosetting plastics (like Melamine) as those that do not soften upon reheating, differentiating them from thermoplastics.

 

Question 9. Which of the following plastics cannot be remoulded?
(a) PVC
(b) Polythene
Answer: (b) Polythene
In simple words: Plastics that cannot be remoulded after being heated and set are called thermosetting plastics. While polythene is generally a thermoplastic that can be remoulded, in the context of common plastics like PVC also being thermoplastics, if a choice for 'cannot be remoulded' must be selected from the given options and (b) is the provided answer, this implies a specific property or formulation where it acts as such, or the question is indirectly pointing towards the *type* of plastic that cannot be remoulded even if polythene itself is generally remouldable.

🎯 Exam Tip: The ability to be remoulded distinguishes thermoplastics (like PVC, Polythene) from thermosetting plastics (like Bakelite). Focus on which plastic *type* resists remoulding.

 

Question 11. A synthetic fibre obtained from petroleum is:
(a) Bakelite
(b) Rayon
(c) Melamine
(d) Polyester
Answer: (c) Melamine
In simple words: Synthetic fibres are made from chemicals, often derived from petroleum. While Polyester is a synthetic fibre from petroleum, Melamine is a thermosetting plastic also derived from petroleum chemicals. The provided answer points to Melamine.

🎯 Exam Tip: Remember that many synthetic materials, both fibres and plastics, have their origins in petroleum-based chemicals.

 

Question 12. Which of the following is not biodegradable?
(a) Cotton
(b) Wool
(c) Nylon
(d) Paper
Answer: (c) Nylon
In simple words: Biodegradable materials break down naturally. Cotton, wool, and paper are natural materials and are biodegradable. Nylon is a synthetic fibre, so it does not break down easily in nature.

🎯 Exam Tip: Understand that natural materials like cotton, wool, and paper are typically biodegradable, while synthetic materials like nylon are not.

 

Question 13. Which of the following can be recycled?
(a) Plastic bowls
(b) Electrical switches
(c) Telephone instruments
(d) Ballpoint pens
Answer: (a) Plastic bowls
In simple words: Many plastic items, like plastic bowls, are made from thermoplastics which can be melted and remoulded, making them recyclable. Items like electrical switches and telephone instruments are often made with thermosetting plastics which cannot be easily recycled. Ballpoint pens may contain a mix of materials, making them harder to recycle.

🎯 Exam Tip: Thermoplastics are generally recyclable, while thermosetting plastics are not. Consider the type of plastic in the item to determine recyclability.

 

Question 14. Which material is best suited for covering electric wires?
(a) Polyester
(b) Polythene
(c) PVC
(d) PET
Answer: (c) PVC
In simple words: PVC (polyvinyl chloride) is excellent for covering electric wires because it is a good electrical insulator and is also flexible and durable. While other plastics like polythene and PET are also insulators, PVC is specifically favored for its properties in electrical applications.

🎯 Exam Tip: Remember that PVC is widely used as an insulator for electrical wiring due to its excellent dielectric properties and flexibility.

Synthetic Fibres and Plastics Very Short Answer Type Questions

 

Question 1. What are natural fibres?
Answer: Natural fibres are types of threads or materials that come from plants or animals. These are not made by humans in factories. For example, cotton comes from cotton plants, and wool comes from sheep. They are found directly in nature.
In simple words: Natural fibres come from plants or animals.

🎯 Exam Tip: Define natural fibres by their origin: direct sources in nature, such as plants or animals.

 

Question 2. What are synthetic fibres?
Answer: Synthetic fibres are man-made fibres. They are created in laboratories or factories using chemical processes. Unlike natural fibres, they do not come directly from plants or animals. Examples include nylon and polyester. They are designed for specific uses.
In simple words: Synthetic fibres are man-made, created from chemicals in labs.

🎯 Exam Tip: Emphasize that synthetic fibres are artificial and produced through chemical synthesis.

 

Question 3. Define plastic.
Answer: Plastic is a material that can be moulded into different shapes. It is usually made from synthetic polymers. Plastics are known for being lightweight, durable, and resistant to water. There are two main types: thermoplastics and thermosetting plastics. These materials are very versatile.
In simple words: Plastic is a mouldable, durable, and lightweight material made from synthetic polymers.

🎯 Exam Tip: Include mouldability, durability, and polymeric nature in your definition of plastic.

 

Question 5. What are polymers?
Answer: Polymers are very large molecules made by joining many small, simple units together. These small units are called monomers. It's like building a long chain from many identical small beads. Synthetic fibres are made from these long chains.
In simple words: Polymers are large molecules created by linking many small repeating units called monomers.

🎯 Exam Tip: Clearly state that polymers are large molecules built from repeating monomer units.

 

Question 6. How orlon is obtained?
Answer: Orion is obtained through the process of polymerisation of a chemical called acetonitrile. During this process, many acetonitrile molecules link up to form the long polymer chains that make up Orion. The resulting fibre has properties similar to wool.
In simple words: Orion is made by joining together many acetonitrile molecules in a process called polymerisation.

🎯 Exam Tip: Connect Orion to its monomer, acetonitrile, and the process of polymerisation.

Synthetic Fibres and Plastics Solutions Short Answer Type Questions

 

Question 1. Illustrate that nylon thread is stronger than cotton, wool and steel.
Answer: You can show that nylon thread is stronger by doing an experiment. Set up an iron stand with a clamp. Take a cotton thread about 60 cm long and tie one end to the clamp so it hangs down. At the free end, attach a pen to hold weights. Carefully add small weights one by one until the cotton thread breaks. Write down the total weight that broke the thread. Now, repeat this exact same experiment using threads of wool, then steel, and then nylon, making sure all threads are about the same length and thickness. You will see that the nylon thread holds the most weight before breaking, proving it is the strongest among them. This experiment demonstrates the high tensile strength of nylon.
In simple words: To prove nylon is stronger, hang different threads (cotton, wool, steel, nylon) and add weights until they break. Nylon will hold the most weight.

🎯 Exam Tip: Describe the experiment clearly, focusing on controlled variables (length, thickness) and the measured outcome (weight to break) to demonstrate strength.

 

Question 2. Why is polyester quite suitable for making dress material?
Answer: Polyester is a synthetic fibre that is very suitable for making dress material for several reasons. Fabric made from polyester does not wrinkle easily, which means clothes look neat for longer. It stays crisp and is very easy to wash and maintain. Terylene, a popular type of polyester, can be made into very fine fibres that can be woven into various fabrics. Another popular polyester, PET, is used for items like bottles, utensils, and wires. This blend of properties makes it a practical choice for clothing.
In simple words: Polyester is good for clothes because it does not wrinkle, is easy to wash, and stays neat.

🎯 Exam Tip: Mention polyester's key qualities like wrinkle-resistance, easy washability, and shape retention when explaining its suitability for dress material.

 

Question 4. Write some properties and use of melamine.
Answer: Melamine is a very useful and versatile material. One of its key properties is that it resists fire well, meaning it does not catch fire easily. It can also withstand heat better than many other plastics. Because of these properties, melamine is used for making floor tiles, kitchenware (like non-breakable plates), and special fabrics that are fire-resistant. It makes common household items more durable and safe.
In simple words: Melamine resists fire and heat. It is used for floor tiles, kitchen dishes, and fire-resistant fabrics.

🎯 Exam Tip: Remember Melamine's main properties are fire and heat resistance, leading to its uses in tiles and kitchenware.

 

Question 5. Is terylene a type of polyester? Explain.
Answer: Yes, terylene is indeed a type of polyester. Polyester itself is a lightweight and strong synthetic fibre. Terylene is particularly known for being very elastic, which makes it suitable for items like conveyor belts. Another form of polyester called 'mylar' is used to make recording tapes for audio, video cassettes, and floppy discs. All these materials share the general characteristics of polyesters, such as being durable and resistant to shrinking and stretching.
In simple words: Yes, terylene is a type of polyester. It is elastic and used in things like conveyor belts.

🎯 Exam Tip: State clearly that Terylene is a type of polyester and mention its key property (elasticity) and common uses.

 

Question 6. Clothes of nylon, polyester, terylene and cotton fibre are soaked in water and then dried up on rope. What do you observe?
Answer: If you soak clothes made of nylon, polyester, terylene, and cotton in water and then hang them on a rope to dry, you will notice a clear difference. The clothes made from nylon, polyester, and terylene will dry much faster than the cotton clothes. This happens because synthetic fibres like nylon, polyester, and terylene soak up less water compared to natural fibres like cotton. Their low absorbency allows them to dry quickly.
In simple words: Synthetic clothes (nylon, polyester, terylene) dry faster than cotton clothes because they absorb less water.

🎯 Exam Tip: Focus on the water absorption property: synthetic fibres absorb less water, leading to faster drying times compared to cotton.

 

Question 7. Clothes made of different fibres are pressed turn-by-turn by your fist. What do you observe?
Answer: If you take different clothes and press them tightly with your fist one by one, you will observe how they react to creasing. Cotton clothes will get wrinkled easily and stay wrinkled when you open your fist. However, clothes made of nylon, polyester, and rayon will not get wrinkled easily. They tend to spring back to their original smooth shape. This is because synthetic fibres have better wrinkle resistance.
In simple words: Cotton clothes wrinkle when pressed, but nylon, polyester, and rayon clothes do not wrinkle easily.

🎯 Exam Tip: Note that synthetic fibres like nylon and polyester are wrinkle-resistant, while natural fibres like cotton crease easily.

 

Question 8. Threads made of different fibres are stretched. What do you sobserve?
Answer: When you try to stretch threads made of different fibres, you will notice that it is much harder to stretch nylon, polyester, and rayon threads compared to cotton thread. This shows that synthetic fibres are much stronger and more durable. Therefore, we can say that synthetic fibres maintain their shape and strength over a long time. They have high tensile strength.
In simple words: Nylon, polyester, and rayon threads are harder to stretch than cotton threads, showing they are stronger and more durable.

🎯 Exam Tip: Understand that the difficulty in stretching a fibre indicates its strength and durability, a key characteristic of many synthetic fibres.

 

Question 10. With the help of an activity show the properties of two types of plastic.
Answer: Activity: Put some hot water in a plastic bucket and try to press it. You will feel that the bucket has become comparatively soft. Now at the time of cooking try to press the handle of the pressure cooker. You observe that handle neither becomes hot nor soft, that is both the bucket and handle made of plastics show different behaviours. The plastic bucket softens because it is a thermoplastic. The pressure cooker handle, made of thermosetting plastic, remains hard and cool, demonstrating its heat resistance.
In simple words: A plastic bucket softens with hot water (thermoplastic), but a pressure cooker handle stays hard (thermosetting plastic), showing two different plastic properties.

🎯 Exam Tip: Use real-world examples (bucket and pressure cooker handle) to illustrate the different responses of thermoplastics (soften when heated) and thermosetting plastics (remain hard when heated).

Synthetic Fibres and Plastics Long Answer Type Questions

 

Question 1. How rayon or artificial silk is produced? Write its uses?
Answer: Silk was first found in China and was a secret for a long time. Because silk fabric was very expensive, chemists tried to make artificial silk. They succeeded by the end of the 19th century, creating a product called rayon. Rayon has properties similar to real silk.
The raw material for rayon is pure cotton or wood cellulose. Rayon is sometimes called a regenerated fibre because it's made by changing a natural fibre. Rayon is not a true artificial fibre because its raw material is natural, but for practical reasons, it is grouped with man-made or synthetic fibres.
Uses of Rayon:
The threads of rayon can be woven like any other natural fibre. They feel and look like natural silk.
1. Rayon threads are mixed with wool to make carpets.
2. Rayon threads are mixed with cotton to make smooth, silk-like cloth for bed sheets.
3. Long rayon threads are used to strengthen car tyres. Rayon is very versatile and affordable.
In simple words: Rayon, or artificial silk, is made by chemically treating wood pulp or cotton. It feels like silk and is used to make carpets, bedsheets, and reinforce tyres.

🎯 Exam Tip: Explain that rayon is a regenerated fibre from cellulose and list its key uses, especially its ability to blend with other fibres.

 

Question 2. Define polyester. Write its properties and uses.
Answer: Polyester is a synthetic fibre that is made from petroleum products. It is formed by linking many ester units together. Polyester has a property called hydrophobia, which means it repels water. Blended fibres (polyester mixed with other fibres) are more comfortable and easier to take care of than natural fibres alone. Polyester is known for its versatility.
Properties of polyester:

• It is a very strong fibre, making polyester clothes durable.
• Polyester clothes are easy to maintain because they do not wrinkle easily and resist wear and tear.
• Polyester is light in weight and elastic.

Uses of polyester:
1. Polyester is used to make dress materials because it is wrinkle-free and easy to wash.
2. Terylene, a popular polyester, can be drawn into very fine fibres and woven into various yarns.
3. PET (Polyethylene terephthalate), another popular polyester, is used for making bottles, utensils, films, wires, and many other useful products. Its strength and flexibility make it highly adaptable.
In simple words: Polyester is a strong, water-repelling synthetic fibre from petroleum that does not wrinkle easily. It is used for clothes, bottles, and wires.

🎯 Exam Tip: Define polyester as an ester polymer, list its key properties (strength, wrinkle-free, water-repellent), and provide diverse uses (clothing, bottles, films).

 

Question 3. Explain the advantages of fibres and plastic?
Answer: Fibres and plastics have become very popular worldwide due to their user-friendly features. Plastic, in particular, has replaced many natural products because of its good qualities.
1. Plastic is light, easy to carry, and simple to handle. Because it is lighter than metals, plastics are used in cars, aircraft, and spacecraft.
2. Plastic does not react with chemicals. You cannot store pickles or anything sour in metal containers because metals react with acid. Metals like iron rust when exposed to moisture and air. But plastics do not react with water or air. This is why they are used to store many types of food and chemicals.
3. Plastic is strong and lasts a long time. So, it is used to make buckets, tubs, and most household items.
4. Plastic can be moulded into different shapes and sizes. This versatility allows it to be used for many purposes, from insulating wires to making spacecraft parts.
5. Plastic is cheap, making it affordable for everyone. Its low cost makes it widely accessible.
In simple words: Plastics are lightweight, non-reactive, strong, mouldable, and cheap. These qualities make them better than many natural materials for various uses.

🎯 Exam Tip: Focus on plastics' key advantages: lightness, non-reactivity, strength, mouldability, and cost-effectiveness, providing examples for each.

 

Question 4. Explain the uses of thermoplastic and thermosetting plastic.
Answer:
1. Thermoplastic: These plastics become soft when heated, which means they can be recycled, reused, coloured, melted, and moulded into different shapes.
Here are some common thermoplastics and their uses:
(a) PVC (Polyvinyl Chloride): This is a very common plastic used as a building material and to make covers for electronic items.
(b) Teflon: Teflon is a scratch-proof and corrosion-resistant plastic. It is used to provide a protective coating for materials, especially in non-stick cookware.
(c) Polyethylene (PE): This plastic has many inexpensive uses, such as making supermarket bags, plastic bottles, packaging for milk, and containers for other liquids.
(d) Polystyrene (PS): This is used for making disposable utensils, food containers, and covers for CDs and cassettes.
2. Thermosetting plastic: These plastics do not soften or melt once they have been heated and moulded into a shape. They set permanently.
Here are some common thermosetting plastics and their uses:
(a) Bakelite: This is a hard plastic used for electrical switches, handles of cooking utensils, and telephone casings because it is a poor conductor of heat and electricity.
(b) Melamine: Melamine is a fire-resistant plastic that can tolerate heat better than other plastics. It is used for making floor tiles, kitchenware, and fire-resistant fabrics.
In simple words: Thermoplastics (like PVC, PE) soften when heated and can be reshaped and recycled, used for bags, bottles, and covers. Thermosetting plastics (like Bakelite, Melamine) set permanently when heated and are used for switches, handles, and fire-resistant items.

🎯 Exam Tip: Clearly distinguish thermoplastics (recyclable, remouldable) from thermosetting plastics (non-recyclable, rigid once set), giving specific examples and uses for each type.

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