Practice Paper
Subject Chemistry
Class VIII Ch- SYNTHETIC FIBRE AND PLASTIC
What are natural fibers?
Ans. Natural fibers are fibers that are derived from natural sources such as plants, animals, and minerals. They are formed by natural processes and are not chemically synthesized.
What are synthetic fibers?
Ans. Synthetic fibers are man-made fibers that are produced through chemical processes. They are created by combining various chemicals and polymers to form fibers with specific properties.
Name two natural fibers obtained from plants.
Ans. Two examples of natural fibers obtained from plants are cotton and jute. Cotton is a soft, fluffy fiber that grows around the seeds of the cotton plant, while jute is a long, shiny fiber obtained from the stem of the jute plant.
Name two natural fibers obtained from animals.
Ans. Two examples of natural fibers obtained from animals are silk and wool. Silk is produced by silkworms to form their cocoons, and it is harvested and spun into thread. Wool is obtained from the fleece or hair of sheep or other animals like goats, alpacas, or llamas.
What is a polymer?
Ans. A polymer is a large molecule made up of repeating subunits called monomers. It is formed by the chemical bonding of monomers, which can be the same or different. Polymers can have a wide range of properties depending on the type of monomers and the arrangement of the polymer chains. Examples of polymers include plastics, rubber, and many types of fibers.
Name the raw material used in the synthesis of nylon.
Ans. The raw material used to synthesize nylon is caprolactam or adipic acid.
Name the repeating units of polyester.
Ans. The repeating units of polyester are ethylene glycol and terephthalic acid.
Name two common forms of polyester.
Ans. Two common forms of polyester are polyethylene terephthalate (PET) and polybutylene terephthalate (PBT).
Name the raw materials used for making synthetic fibers.
Ans. The raw materials used for making synthetic fibers vary depending on the specific type of fiber. Some common raw materials include petroleum-based chemicals such as ethylene and propylene, as well as natural materials like cellulose from plants.
What are thermosetting plastics?
Ans. Thermosetting plastics are a type of polymer that, once molded and cured, cannot be re-melted or reformed by heating. They undergo a chemical change during the curing process, forming a rigid and durable structure. Thermosetting plastics retain their shape and properties permanently once they are set.
Give two examples of thermoplastics.
Ans. Two examples of thermoplastics are polyethylene and polyvinyl chloride (PVC).
Give two examples of thermosetting plastics.
Ans. Two examples of thermosetting plastics are epoxy resin and phenolic resin.
Why is bakelite used in making electrical switches?
Ans. Bakelite is used in making electrical switches because it is a thermosetting plastic that has excellent electrical insulation properties. It can withstand high temperatures and is resistant to electricity, making it a suitable material for electrical applications.
Name the chemicals which give fruits their characteristic smell.
Ans. The chemicals that give fruits their characteristic smell are primarily volatile organic compounds. Examples- Ethylene, which gives off a sweet aroma in ripening fruits, and esters,, which give fruits like bananas their distinctive scent.
Name the two different types of plastics.
Ans. The two different types of plastics are thermoplastics and thermosetting plastics.
Name the man-made fiber made of wood pulp.
Ans. The man-made fiber made of wood pulp is called rayon.
Name the fabric, which resembles wool.
Ans. The fabric that resembles wool is called acrylic.
Why is nylon used for making carpets, toothbrush bristles, and tires?
Ans. Nylon is used for making carpets, toothbrush bristles, and tires because of its strong and durable properties. It is resistant to abrasion and can withstand heavy foot traffic in carpets.
Nylon is also flexible, making it suitable for toothbrush bristles that need to be strong yet gentle on the gums.
In tires, nylon provides reinforcement and improves their strength and resilience.
Handles of frying pans are made of plastic. Why?
Ans. Handles of frying pans are often made of plastic due to its insulating properties. Plastic handles stay cool to the touch even when the pan is heated, providing a safe and comfortable grip for users while cooking.
Electrical wires have a covering of plastic. Why?
Ans. Electrical wires have a covering of plastic, usually PVC due to its insulating properties. Plastic is a non-conductive material that helps prevent the flow of electricity and protects against electrical shocks or short circuits. It also provides a protective barrier against moisture, chemicals, and physical damage.
How are clothes, fabrics, and fibers related to each other?
Ans. Clothes, fabrics, and fibers are all interrelated.
Fibers are the basic building blocks of fabrics. Fabrics are formed by weaving or knitting fibers together to create a textile material.
Clothes, on the other hand, are made from fabrics and are used to cover and protect the body, provide comfort, and express personal style. Fibers can be natural, such as cotton or silk, or synthetic, such as polyester or nylon, and they serve as the raw materials for creating fabrics and, subsequently, clothes.
Name the synthetic fiber which is a cheap substitute of silk.
Ans. The synthetic fiber that is a cheap substitute for silk is called rayon. Rayon is made from regenerated cellulose, often derived from wood pulp. It is known for its soft and smooth texture, which closely resembles silk. Rayon is more affordable compared to silk while still offering similar drape and luster, making it a popular choice for producing cost-effective silk alternatives.
Why is nylon used in making clothes?
Ans. Nylon is used in making clothes because of its desirable properties.
It is a lightweight and strong synthetic fiber that is highly resistant to abrasion and tear. Nylon fabrics are durable, flexible, and quick-drying.
They have good shape retention, are easy to care for, and can be blended with other fibers to enhance specific characteristics.
These properties make nylon suitable for various types of clothing, including activewear, swimwear, hosiery, and outerwear.
Although rayon is obtained from a natural source, wood pulp, yet it is a man-made fiber. Give reasons.
Ans. Rayon is considered a man-made fiber despite being derived from a natural source, wood pulp because it undergoes significant chemical processing and manufacturing to transform the raw material into usable fiber. The wood pulp is treated with chemicals, dissolved, and then extruded through spinnerets to create filaments, which are then chemically treated again to solidify them into fibers. This extensive manufacturing process distinguishes rayon as a man-made fiber.
Nylon is used in making many articles. Name four of them.
Ans. Four articles commonly made from nylon are:
Clothing: Nylon is used to make various types of garments. Examples- are jackets, shirts, pants, stockings, and sportswear.
Hosiery: Nylon is a popular material for producing socks, tights, and other types of hosiery due to its durability and stretchability.
Luggage and bags: Nylon is commonly used in the manufacturing of luggage, backpacks, handbags, and other types of bags due to its strength and lightweight nature.
Carpets and rugs: Nylon is a common material for making carpets and rugs due to its resilience, stain resistance, and ability to retain vibrant colors.
26. Why are polyesters preferred over natural fibers for making dress material?
Ans. Polyesters are preferred over natural fibers for making dress material due to several reasons:
Durability: Polyester fibers are strong and resistant to stretching, shrinking, and wrinkling, making them more durable than many natural fibers.
Easy maintenance: Polyester fabrics are easy to care for as they are resistant to wrinkling and have good stain resistance. They can be machine-washed, dried quickly, and require minimal ironing.
Moisture wicking: Polyester has moisture-wicking properties, it draws moisture away from the body and dries quickly.
Versatility: Polyester can be blended with other fibers to enhance certain properties, such as adding stretch with elastane or improving breathability with natural fibers.
27. What is PET? What is its use?
Ans. PET stands for polyethylene terephthalate. It is a type of polyester widely used in the production of various items, particularly plastic bottles for beverages and food products. PET is known for its clarity, strength, lightweight nature, and recyclability. It is commonly used for packaging water, soft drinks, juices, condiments, and other liquids.
28. What are acrylics? What are its uses?
Ans. Acrylics are synthetic fibers made from polymers of acrylic monomers. They are known for their softness, warmth, and wool-like feel. Acrylic fibers are commonly used as a substitute for wool in various applications. Some uses of acrylics include:
Clothing and textiles: Acrylic fibers are used to make sweaters, hats, scarves, blankets, and other winter wear due to their warmth and softness.
Home furnishings: Acrylic is used in making upholstery fabrics, curtains, carpets, and rugs due to its durability and resistance to fading.
Outdoor applications: Acrylic fibers are often used in outdoor fabrics such as awnings, outdoor furniture upholstery, and marine upholstery due to their resistance to sunlight and moisture.
Craft materials: Acrylic yarns are widely used in knitting and crocheting projects due to their affordability and availability in a wide range of colors.
28. Why should one not wear polyester clothes while working in the kitchen or laboratory?
Ans. Polyester clothes should not be worn while working in the kitchen or laboratory because polyester is a synthetic fiber that has low heat resistance. When exposed to high temperatures, polyester can melt or shrink, potentially causing burns.. Similarly, in laboratories, where chemicals and flammable substances are present, wearing synthetic fibers like polyester can increase the risk of injury in case of accidents or chemical spills.
29. Why are synthetic fibers preferred as a clothing material?
Ans. Synthetic fibers are preferred as clothing material for several reasons:
Durability: Synthetic fibers such as polyester and nylon are known for their strength and resistance to wear and tear, making them more durable than many natural fibers.
Easy care: Synthetic fibers are often easier to care for than natural fibers.
Moisture management: Synthetic fibers draw moisture away from the body and dry quickly.
Versatility: Synthetic fibers can be engineered to possess specific characteristics such as stretchability, water resistance, or thermal insulation.
Affordability: Synthetic fibers are often more cost-effective to produce than natural fibers, making them more accessible and affordable for consumers.
30. Why is melamine used for making kitchenware and fabrics which resist fire?
Ans. Melamine is used for making kitchenware and fabrics that resist fire due to its unique properties.
Melamine is a thermosetting plastic that is highly resistant to heat and fire.
It has a high melting point, allowing it to withstand high temperatures without deforming or releasing toxic fumes.
Melamine also has excellent insulation properties, which further enhance its fire resistance.
Melamine is durable and resistant to scratches and stains, making it a suitable material for kitchenware and fabrics that require longevity and easy maintenance.
31. Why are plastic containers preferred over containers made of glass and clay for storing foodstuffs?
Ans. Plastic containers are preferred for storing foodstuffs due to several reasons:
Durability: Plastic containers are less fragile than glass and clay, making them more susceptible to breakage during handling and transportation.
Lightweight: Plastic containers are lighter than glass and clay, making them easier to carry and store.
Cost-effective: Plastic containers are generally more affordable than glass and clay containers, making them a cost-effective choice for mass production and distribution.
Versatility: Plastic containers come in a variety of shapes and sizes, offering greater flexibility in storing different types of foodstuffs, from liquids to solid items.
32. Acrylic is considered a cheap substitute for wool. Give reasons.
Ans. Acrylic is considered a cheap substitute for wool due to several reasons:
Cost: Acrylic fibers are generally less expensive to produce compared to wool. The raw materials used in acrylic production, such as petroleum or natural gas, are more affordable than the resources required for wool production, such as sheep farming and shearing.
Availability: Acrylic fibers can be easily manufactured in large quantities, making them readily available in the market. On the other hand, wool production is limited by factors such as the availability and breeding of sheep.
Maintenance: Acrylic fibers are relatively easy to care for compared to wool. They are machine washable and can withstand regular wear and tear without losing their shape or becoming damaged. Wool, on the other hand, requires more delicate handling and often requires special cleaning methods.
33. Define (i) Fabric ( ii)Cloth.
Ans. (i) Fabric: Fabric refers to any material made through the process of weaving, knitting, or bonding fibers together. It is a flexible material that can be used to create various items, including clothing, upholstery, and bedding. Fabrics can be made from natural fibers (such as cotton, silk, or wool) or synthetic fibers (such as polyester or nylon).
(ii) Cloth: Cloth specifically refers to a piece of fabric that has been cut or woven to a specific size or shape. Cloth is the end product that is used to make garments, household items, or other fabric-based products.
34. Write the properties and uses of rayon?
Ans. Properties of Rayon:
Softness: Rayon has a soft and smooth texture, resembling natural fibers like silk. It is comfortable to wear and drapes well, making it suitable for clothing items such as dresses, blouses, and scarves.
Breathability: Rayon is a breathable fabric that allows air to pass through, making it suitable for warm weather or humid climates. It provides comfort by preventing excessive heat and moisture buildup.
Versatility: Rayon can mimic the appearance of various fabrics, such as cotton, silk, or linen. It can be woven or knitted to create different textures, making it versatile for different types of garments.
Uses of Rayon:
Clothing: Rayon is commonly used to make garments such as dresses, blouses, skirts, and shirts due to its softness, draping quality, and comfort.
Home Furnishings: Rayon fabrics are also used for upholstery, curtains, and bed linens, adding a touch of elegance and comfort to home interiors.
Industrial Applications: Due to its absorbency and strength when wet, rayon is used in medical supplies, bandages, and non-woven products like wipes.
35. Write three disadvantages of synthetic fibers.
Ans. Three disadvantages of synthetic fibers are:
Environmental Impact: Synthetic fibers, such as polyester and nylon, are derived from petrochemicals, which are non-renewable resources. The production of synthetic fibers consumes a significant amount of energy and releases harmful pollutants into the environment, contributing to air and water pollution.
Lack of Breathability: Synthetic fibers are generally less breathable compared to natural fibers like cotton or wool. They do not allow for proper air circulation, which can result in discomfort and sweating when worn close to the skin. This can be a drawback in clothing and textiles where breathability is desirable.
Microplastic Pollution: Synthetic fibers shed tiny microplastic particles during washing, which find their way into rivers, lakes, and oceans. These microplastics pose a threat to marine life and can enter the food chain, ultimately affecting human health.
36. (a) Name a fiber that can be used as a cheap substitute for silk.
(b)Write four properties of nylon that make it a popular fiber for making clothes?
(c) What is terylene?
(a) Polyester can be used as a cheap substitute for silk.
(b) Four properties of nylon that make it a popular fiber for making clothes are:
Strength and durability,
Moisture resistance,
Elasticity,
Easy care.
(c) Terylene is a brand name for polyester fiber. It is a synthetic polymer that belongs to the polyester family of fibers. Terylene is known for its strength, durability, and wrinkle resistance, making it a popular choice for various applications, including clothing, upholstery, and packaging materials. It is often used as a substitute for silk due to its similar luster and drape. Terylene fibers can be woven or knitted into fabrics with different textures and finishes, providing versatility in their use.
37. (a) When we say that plastics are non-biodegradable, what does it mean?
(b)Write two fiber-wise practices.
Ans. (a) We say that plastics are non-biodegradable because they cannot be broken down or decomposed by natural biological processes, such as the actions of bacteria or other microorganisms. Plastics are made of polymers that are not easily broken down by biological agents found in the environment, leading to their persistence in the environment for a very long time.
(b) Two fiber-wise practices:
Reduce, Reuse, and Recycle: This practice involves minimizing the use of fibers by opting for reusable items or products made from sustainable materials. When fibers are used, it is essential to recycle them whenever possible to prevent unnecessary waste and promote a circular economy.
Use Sustainable Fiber Alternatives: Choosing fibers that are eco-friendly and sustainable is crucial. Examples of sustainable fibers include organic cotton, hemp, bamboo, and lyocell, which have a lower environmental impact compared to conventional fibers like polyester or nylon. Opting for these alternatives helps reduce the ecological footprint of the textile industry.
38. What are the advantages of using synthetic fiber?
Ans. There are several advantages of using synthetic fibers:
Durability: Synthetic fibers, such as polyester and nylon, are known for their strength and durability. They have high resistance to wear and tear.
Low cost: Synthetic fibers are generally less expensive to produce compared to natural fibers.
Easy maintenance: Synthetic fibers are often easy to care for and require minimal maintenance.
39. State True or False
(i) Nylon is a polymer.
(ii) All polymers are natural materials.
(iii) Polythene is a thermosetting plastic.
(iv) Starch, cellulose, proteins, silk, and rubber are natural polymers.
(v) Polyethylene terephthalate (PET) is used in making clothes.
Ans. (i) True. (ii) False. (iii) False. (iv) True. (v) True.
40. Why is the government trying to ban plastic bags and promote paper bags though they are stronger than paper bags?
The government is likely trying to ban plastic bags and promote paper bags due to environmental concerns.
Plastic bags are known to cause significant harm to the environment, taking hundreds of years to decompose.
Paper bags, while not as strong, are biodegradable and can be recycled.
The focus is on reducing plastic waste and encouraging sustainable alternatives.
There may be efforts to promote reusable bags as the most eco-friendly option.
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