Answer: Some fibres are called synthetic fibres because they are made by humans using chemicals rather than being obtained from natural sources. These fibres are produced through chemical processes using petrochemicals.

Answer: (b) it is obtained from wood pulp.

Answer:
(a) Synthetic fibres are also called man-made or artificial fibres.
(b) Synthetic fibres are synthesised from a raw material called petrochemicals.
(c) Like synthetic fibres, plastic is also a polymer.

Answer: The following examples indicate that nylon fibres are very strong:

• Nylon is used for making parachutes which need to be strong enough to hold a person safely.
• It is used for making ropes for rock climbing which need to support a person’s weight.
• Nylon is used in making car seat belts which need strength to protect passengers during accidents.
• It is used for making fishing nets which need to withstand the weight of fish and water pressure.

Answer: Plastic containers are favoured for storing food because of the following reasons:

• Plastics are non-reactive and do not react with the food stored in them, keeping the food safe.
• They are lightweight and strong, making them easy to handle and transport.
• They are durable and do not break easily like glass containers.
• They can be made airtight, which helps in keeping the food fresh for a longer time.
• They are inexpensive compared to containers made of other materials.

Answer:

Answer:

(a) Saucepan handles: Saucepan handles are made of thermosetting plastics because these plastics are poor conductors of heat. When a saucepan is heated during cooking, thermosetting plastic handles do not get hot, making them safe to hold. Also, they do not soften or deform even when exposed to high temperatures.

(b) Electric plugs/switches/plug boards: These are made of thermosetting plastics because:

• Thermosetting plastics are poor conductors of electricity, providing good insulation and preventing electric shocks.
• They do not soften when heated, so they maintain their shape even if there is slight heating due to electric current.
• They are durable and can withstand wear and tear.

Answer:

The items in the “can be recycled” column are mostly made of thermoplastics, while those in the “cannot be recycled” column typically contain thermosetting plastics.

Answer: Rana should buy cotton shirts for summer. This is because:

• Cotton is a natural fibre that has more capacity to absorb moisture (sweat) than synthetic materials.
• In summer, we sweat more due to high temperatures. Cotton absorbs this sweat, allowing it to evaporate from its surface, which helps in keeping the body cool.
• Synthetic shirts do not absorb sweat well, which can make the body feel sticky and uncomfortable in hot weather.
• Cotton is breathable, allowing air to pass through the fabric, which helps in cooling the body.
• Cotton is softer on the skin and less likely to cause irritation in hot weather.

Answer: Following are the examples that show that plastics are non-corrosive in nature:

• Plastic containers do not react with food items or chemicals stored in them, while metal containers might react with certain acidic foods.
• Plastic water pipes do not corrode or rust when exposed to water, unlike iron pipes.
• Plastic coatings are applied to metal objects to prevent them from corrosion.
• Laboratory equipment made of plastic can safely store most chemicals without being damaged.
• Plastic objects left outdoors do not rust when exposed to moisture and air, unlike metals.

Answer: No, the handle and bristles of a toothbrush should not be made of the same material. This is because:

• The handle of a toothbrush needs to be rigid and strong to provide a good grip during brushing. It is typically made of hard plastic (like polypropylene).
• The bristles need to be soft and flexible to clean teeth effectively without damaging the gums. They are usually made of nylon or other soft synthetic fibres.
• If the bristles were made of the same hard plastic as the handle, they would be too stiff and could harm the gums and tooth enamel.
• If the handle were made of the same soft material as the bristles, it would be too flexible and would not provide proper support for brushing.

Different functions require different materials with appropriate properties.

Answer: The advice “Avoid plastics as far as possible” is sound for several important reasons:

• Environmental Impact: Most plastics are non-biodegradable and take hundreds of years to decompose naturally. They accumulate in the environment, causing pollution.
• Wildlife Danger: Plastic waste, when consumed by animals (like cows, birds, or marine creatures), can choke their respiratory system and cause death.
• Air Pollution: When burned, plastics release toxic fumes and harmful gases that contribute to air pollution.
• Drainage Problems: Discarded plastic bags often block drains and sewers, causing water logging and breeding grounds for disease-carrying insects.
• Resource Depletion: Plastics are made from petrochemicals derived from non-renewable fossil fuels.
• Health Concerns: Some plastics may leach harmful chemicals into food and water under certain conditions.

However, it’s important to recognize that plastics do serve important functions in modern life, particularly in medical applications, food safety, and technology. The key is to use plastics responsibly, minimize single-use plastics, and ensure proper disposal and recycling.

Answer:

• (i) Polyester — (d) Fabrics do not wrinkle easily
• (ii) Teflon — (c) Used to make non-stick cookware
• (iii) Rayon — (a) Prepared by using wood pulp
• (iv) Nylon — (b) Used for making parachutes and stockings

Answer: The statement “Manufacturing synthetic fibres is actually helping the conservation of forests” is partially true for the following reasons:

• Synthetic fibres reduce our dependency on natural fibres like cotton and jute, which require agricultural land for cultivation.
• By using synthetic alternatives to wool (like acrylic), we reduce pressure on sheep rearing, which can lead to overgrazing of forests and grasslands.
• Rayon, though made from wood pulp, requires less wood compared to the amount needed for paper production for the same weight.
• The production of natural fibres requires large areas of land that might otherwise remain forested.

However, this perspective is incomplete because:

• Synthetic fibres are made from petrochemicals derived from non-renewable resources like petroleum.
• The manufacturing process of synthetic fibres involves chemical processes that can cause pollution if not properly managed.
• Synthetic fibres are non-biodegradable and contribute to long-term environmental pollution.

A balanced approach would be to use both natural and synthetic fibres responsibly, with emphasis on sustainable production methods and proper waste management.

Answer: Activity to show that thermoplastic is a poor conductor of electricity:

Materials required:

• A small bulb with holder
• A battery
• Connecting wires
• A piece of thermoplastic (like a polythene sheet)

Procedure:

1. Set up an electric circuit by connecting the bulb to the battery using wires.
2. Leave a small gap in the circuit.
3. Complete the circuit and observe that the bulb glows.
4. Break the circuit again and place the thermoplastic in the gap.
5. Observe what happens to the bulb.

Observation: When the thermoplastic is placed in the gap, the bulb does not glow.

Conclusion: Since the bulb does not glow when the thermoplastic is placed in the circuit, it shows that thermoplastic does not allow electricity to pass through it. This proves that thermoplastic is a poor conductor (or good insulator) of electricity.

Answer:

Answer: Rayon is called artificial silk because:

• It has properties similar to silk, such as softness and luster.
• It can be woven like silk into fabrics with a similar drape and appearance.
• It was developed as a cheaper alternative to natural silk.
• When made into fabric, it visually resembles silk but is manufactured artificially from wood pulp through chemical processing.

Answer:

Advantages:

• Strong and durable – last longer than many natural fibres
• Affordable and readily available
• Easy to maintain – quick drying and wrinkle-resistant
• Can be engineered for specific purposes
• Do not require large agricultural lands for production

Disadvantages:

• Most are non-biodegradable, causing environmental pollution
• Poor absorption of water, making them uncomfortable in hot weather
• Melt when exposed to high temperatures or fire
• Can cause skin allergies in some people
• Made from non-renewable resources (petrochemicals)

Answer: Following the 4R principle (Reduce, Reuse, Recycle, Recover) with respect to plastics is essential because:

• Reduce: Minimizing plastic use reduces the amount entering the environment as waste. This helps conserve the non-renewable petroleum resources used to make plastics.
• Reuse: Using plastic items multiple times extends their life, reduces the need for new production, and decreases waste generation.
• Recycle: Converting plastic waste into new products reduces landfill usage and saves energy compared to making new plastic from raw materials.
• Recover: Extracting energy from plastic waste through processes like incineration helps recover some value from plastics that cannot be recycled.

Following these principles helps address environmental problems caused by plastics such as pollution, harm to wildlife, and the depletion of natural resources, while still allowing us to benefit from the useful properties of plastics.

Answer:

Answer: A simple burning test can distinguish between natural and synthetic fibers based on their behavior when burned:

Procedure:

1. Take a small strand of the fiber to be tested.
2. Hold it with tweezers or pliers.
3. Bring it near a flame (carefully).
4. Observe how it burns, the smell, and the residue left behind.

Observations:

This test helps identify whether a fabric is made from natural or synthetic materials.

Answer: Environmental advantages of using natural fibers over synthetic ones include:

• Biodegradability: Natural fibers decompose naturally in the environment, while synthetic fibers can persist for hundreds of years.
• Renewable resources: Natural fibers come from plants and animals that can be regrown or raised again, while synthetic fibers come from non-renewable petroleum resources.
• Lower energy consumption: Production of natural fibers generally requires less energy compared to the manufacturing processes for synthetic fibers.
• Carbon sequestration: Plants used for natural fibers (like cotton, jute, hemp) absorb carbon dioxide during growth, helping reduce greenhouse gases.
• Less pollution: Production of natural fibers typically releases fewer harmful chemicals and pollutants compared to synthetic fiber manufacturing.
• No microplastic shedding: When washed, synthetic fabrics release microplastics that pollute water bodies, while natural fibers do not.

Answer: Bioplastics are plastics derived from renewable biomass sources such as vegetable oils, corn starch, or microbiota, rather than fossil-fuel based sources.

Differences between bioplastics and conventional plastics:

Bioplastics represent an important step toward more sustainable materials, though they still have limitations and are not a complete solution to plastic pollution.

Answer: Synthetic fibers are preferred over natural fibers in certain applications due to their specific properties:

• Sports clothing: Synthetic fibers like polyester and nylon are used because they are lightweight, quick-drying, and can wick moisture away from the body, making them ideal for athletic wear.
• Protective gear: Aramid fibers (like Kevlar) are used in bulletproof vests and helmets due to their exceptional strength-to-weight ratio, which natural fibers cannot match.
• Medical applications: Synthetic fibers are used for surgical sutures, implants, and bandages because they can be sterilized, are non-allergenic, and can be engineered to specific requirements.
• Outdoor equipment: Tents, backpacks, and outdoor furniture use synthetic fibers for their water resistance, UV stability, and durability in harsh conditions.
• Safety equipment: Parachutes and climbing ropes use nylon because of its exceptional strength and reliability, which is critical for life-saving equipment.
• Industrial applications: Synthetic fibers are used in filters, conveyor belts, and reinforcement materials because they resist chemicals, heat, and mechanical stress better than natural alternatives.

In these applications, the specific engineered properties of synthetic fibers provide advantages that natural fibers cannot offer, despite the environmental benefits of natural materials.

Answer: The discovery of synthetic fibers has significantly transformed our lifestyle in numerous ways:

• Clothing accessibility: Synthetic fibers made clothing more affordable and accessible to everyone. Fabrics became less expensive, allowing more people to own a variety of clothing.
• Easy maintenance: Synthetic clothes are easier to wash, dry quickly, and often require less ironing, saving time and effort in daily life.
• Specialized clothing: Sports and performance wear made from synthetics has revolutionized athletics by providing moisture-wicking, lightweight options that enhance performance.
• Durable products: Items like backpacks, luggage, and outdoor equipment last longer due to the durability of synthetic fibers, changing how we travel and enjoy outdoor activities.
• Medical advancements: Synthetic fibers in medical applications have improved healthcare through better surgical sutures, implants, and sanitary products.
• Safety improvements: Products like seatbelts, airbags, and protective gear made from strong synthetic fibers have saved countless lives.
• Space exploration: Synthetic materials have enabled space suits and equipment that can withstand extreme conditions, making space exploration possible.
• Fashion innovation: Synthetic fibers allowed for new textures, colors, and designs in fashion that weren’t possible with only natural fibers, expanding creative possibilities.

While these changes have brought convenience and innovation, they’ve also created environmental challenges that we now need to address through more sustainable practices and materials.