The shopkeeper showed her blankets made up of acrylic fibres as well as made up of wool. Explain. Today, formica and medium density fiberboard (MDF) are still made by mixing bakelite with paper pulp or … The exemplar has been provided by the National Council of Educational Research & Training (NCERT) and the candidates can check it from below for free of cost. Melamine is a versatile material. So, a polymer is made of many repeating units. Why is it so? These are prepared from a type of synthetic fibre, called acrylic. Addition polymers: Polymers are formed by the repeated addition of monomers with double and triple bonds. Why do people always prefer to choose plastic instead of using metals? Name some common articles made from fibres. This preview shows page 1 - 2 out of 2 pages. Question 7. iv) Synthetic fibres are extremely fine and shiny. Polythene and PVC are some of the examples of thermoplastics. A. Bakelite B. Melamine C. Branched D. Poly-vinyl chloride 9. Plastic takes several years to decompose; it is not environment friendly. Bakelite and melamine are some examples of thermoplastics Answer: False Correct statement: Bakelite and and melamine are some examples of thermosettingplastic. She preferred to buy an acrylic blanket”. Sometimes people are very careless and throw the wrappers of chips, biscuits and other eatables on the road or in parks or picnic places. 1) Teflon, a kind of plastic is used as a coating to manufacture non-stick cookware. What do you mean by “thermoplastic” and “thermosetting plastic”? In the process it releases lots of poisonous fumes into the atmosphere causing air pollution. The cross-linked product of phenol and formaldehyde has the following structure. We need not produce resources on large scale which may lead to exploitation of natural resources. The 4 R principle is: 4R means Reduce, Reuse, Recycle and Recover. A material which is not easily decomposed by natural processes is termed as non-biodegradable. Examples – Bakelite, melamine, etc. Question 14. Bakelite items, particularly jewelry and radios, have become a popular collectible. Terylene is a popular polyester. This is because of their light weight, lower price, good strength and easy handling. Download NCERT Books 2020-21 based on new CBSE Syllabus for session 2020-2021. A material which gets decomposed through natural processes, such as action by bacteria, is called biodegradable. Answer: Thermosetting – bakelite, melamine Thermoplastics – combs, toys. Besides, the burning process in the synthetic material is quite slow and it does not get completely burnt easily. Bakelite and Melamine are the example of thermosetting plastic. Jammu & Kashmir has banned the use of plastic bags. Why do people choose this type of sweaters? Write down their some features. a) Nylon. The word ‘polymer’ comes from two Greek words; “poly” meaning “many” and “mer” meaning “part/unit”. These are reactive molecules and are usually linked to each other by covalent bonds. The formation process of these two types of plastics also differs. A material which gets decomposed through natural processes, such as action by bacteria, is called biodegradable. Teflon is a special plastic on which oil and water do not stick. We use many articles made from nylon, such as socks, ropes, tents, toothbrushes, car seat belts, sleeping bags, curtains etc. There are some plastic articles which can bend easily while some break when forced to bend. Some examples are natural gas or even corn, wheat, or rice. Many such small units combine to form a large single unit called a polymer. It is used for making floor tiles, kitchenware and fabrics which resist fire. These monomers add together to form a long chain to form a product with spe… Which type of fibre is used in his sweater? How does plastic create problems for them? Why rayon is referred as “artificial silk” or “man-made fibre”? These are called synthetic fibres. Give example to show that plastics are non-corrosive in nature. Synthetic fibres are more durable and affordable which makes them more popular than natural fibres. After reading NCERT Books, you have just to go through these questions to prepare the entire chapter for exams. Can you suggest some methods to limit its consumption? A synthetic fibre is also a chain of small units joined together. MCQ Questions for Class 12 Chemistry with Answers were prepared based on the latest exam pattern. After studying the NCERT Books, important Questions provide a proper revision of the chapter for exams. They do not decompose (or rot) easily. This fibre was called rayon or artificial silk. They are available in a variety of colours. Why are the chemicals in the laboratory stored in plastic containers ? Most of the thermoplastics can be recycled. They become hard and infusible on heating and cannot be softened again. Generally, shirt, trousers, bed sheets, blankets, curtains, table-cloths, towels and dusters are made from different kinds of fibres. A. Bakelite B. Melamine C. Branched D. Cross-linked 10. i) Avoid the use of plastics as far as possible. v) Do not throw plastic waste in the street on the pavement or in drains. Polymers are generally formed by the addition of a network of structural units or small molecules called monomers. Synthetic fibre: There are some fibres which made from chemical substances, and they do not obtain from plant or animal sources. c) Melamine plastic. It is used for non-stick coating on cook-wares. But plastics do not react with water and air. “Generally, we see in a garbage dump where animals eating garbage”. Cotton is a natural polymer, called cellulose. b) Rayon. Will you help her? Answer: Plastics are non-reactive, so they can be used for storing chemicals. Fire proof plastic uniform worn by fire fighters has a coating of _____ to make it fire resistant. Nylon is also used for making parachutes and ropes for rock climbing. It is better to recycle the plastic waste. Such fibre was obtained by chemical treatment of wood pulp. vi) Try to minimise the use of plastic materials e.g. ii) Buy products without a little plastic packaging. Can you write a name of a “Natural polymer”? Cellulose is made up of a large number of glucose units. Burning of plastics and synthetic fabrics produces lots of poisonous gases causing air pollution. When we add hot water to a plastic bottle, it gets deformed. Bataan Peninsula State University in Balanga, Bataan Peninsula State University in Balanga • BSME 101, Cracking the Sat Biology E_M Su - The Princeton Review.pdf, Bataan Peninsula State University in Balanga • CEA 0223, Bataan Peninsula State University in Balanga • BSAR 13-00215, Bataan Peninsula State University in Balanga • BSME 5C, Bataan Peninsula State University in Balanga • NURSING 103, Bataan Peninsula State University in Balanga • CHEM MISC. Can you guess why? Bakelite definition, a brand name for any of a series of thermosetting plastics prepared by heating phenol or cresol with formaldehyde and ammonia under pressure: used for radio cabinets, telephone receivers, electric insulators, and molded plastic ware. There are some of the steps which contribute towards the reducing the use of plastic materials by us. Such as animals, trees, cotton, jute. Acrylic blankets are cheap, light in weight, more durable and are available in variety of colours and designs. Justify the statement. It resists fire and can tolerate heat better than other plastics. We can store various kinds of chemicals and other materials in plastic containers because they are non-reactive and does not react with water and air. Synthetic fibres possess unique characteristics which make them popular dress materials. Therefore, people always prefer to choose plastic instead of using metals. 8 Bakelite and Melamine are examples of. What Policies Can Help Students Affected by COVID-19? The term Bakelite is sometimes used in the resale market to indicate various types of early plastics, including Catalin and Faturan, which may be brightly colored, as well as items made of Bakelite material. Instead we can reuse them. 2) Bakelite is a poor conductor of heat and electricity so, it is used for making electric switches and handles of the utensils. Orientation of monomer units in a polymer molecule, A type of polymer wherein the side groups are arranged in an irregular or random, Monomers made of alkenes usually undergo addition polymerization due to their. Would you like to help him? The plastic material chokes the respiratory system of these animals, or forms a lining in their stomachs and can be the cause of their death. “As a responsible citizen remember the 4R principle”. Each small unit is actually a chemical substance. Why do people always prefer to choose plastic instead of using metals? This is actually a disadvantage of synthetic fibres. Answer. Such as animals, trees, cotton, jute. Class 8 Science Chapter 3 Important Questions are given below updated for new academic session 2020-21. The polybags carelessly thrown here and there are responsible for clogging the drains, too. Such as plastic. They are not corroded easily. Some important properties of bakelite are listed below. Example : Polyethene, Polyvinyl chloride (PVC) etc. Being lighter as compared to metals, plastics are used in cars, aircrafts and spacecrafts, too. A material which is not easily decomposed by natural processes is termed as non-biodegradable. These are called thermosetting plastics. Such as plastic. Answer: (c) 10. The coating on modern non- stick cookware and electric iron is of Orientation of monomer units in a polymer molecule A. Tacticity B. Graft C. Linear D. Monomer arrangement 11. If the clothes catch fire, it can be disastrous. Write down their some features. “Avoid the use of plastic as for as possible”. Check the below NCERT MCQ Questions for Class 12 Chemistry Chapter 15 Polymers with Answers Pdf free download. Try to minimise the use of plastic materials. The wool obtained from natural sources is quite expensive, whereas clothes made from acrylic are relatively cheap. Today if we think of storing a food item, water, milk, pickles, dry food, etc., plastic containers seem most convenient. Reducing the usage is a method of conservation of resources. It contributes sturdy structure to the plants. Polyester is another synthetic fibre. Why? Plastic causes environmental pollution. It remains crisp and is easy to wash. The fabric melts and sticks to the body of the person wearing it. Hence, “manufacturing synthetic fibres is actually helping conservation of forests”. Plastics are often made from petrochemicals like crude oil but can also be made from other materials. On the other hand, there are some plastics which when moulded once, cannot be softened by heating. The first human-made plastics were actually made using cellulose from plants. Explain the statement. For example, polyethene and polyvinyl chloride. ii) Synthetic fibres are light, wrinkled free and easy to maintain. Question 12. It can be quickly molded. Question 13. They can be easily washed at home. a) Nylon b) Rayon c) Melamine plastic d) Silk. Bakelite Structure. iii)Synthetic fibres are less expensive and readily available in the market. Tutorial for Learning C Programming: Is It Possible to Learn the Programming Language Online. The chemical formula of bakelite can be written as (C 6 H 6 O-CH 2 OH) n. What are the Desirable Properties of Bakelite? Important Questions and Extra questions are prepared to revise the chapter 3 of Class 8 Science. Although rayon is obtained from a natural source, wood pulp, yet it is a man-made fibre. 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