Does this imply that it is a polymer? A synthetic fibre classified as polyester (8) 7. Our pots use genuine Bakelite handles to last the generations). MySQL Connector/NET 8.0 API Reference. Substance made up of large number of smaller molecules (7) 4. They are used for making cabinets of radio, television, telephone sets, water tanks, water pipes, electric switches, cups plates, dinner sets, etc. 18) What is nylon ? A type of fibre obtained naturally from cocoon (4) 6. This is why plastic bottles are commonly used to store chemicals in a chemistry laboratory. In the 1930s cast Bakelite, along with many other competing phenolic resins, enjoyed a vogue in colourful costume jewelry and novelties. Class â 8. Careless disposal of plastic bags, chokes, drains and blocks the soil. 22) What is PET ? 6. Note down the total weight required to break the thread. The burning plastic releases lots of poisonous fumes into the atmosphere causing air pollution. However, rayon is regenerated from cellulose and it doesn’t melt on burning, rather it flares up like paper and smells like it. Non-Biodegradable : A material which is not easily decomposed by natural processes is called non-biodegradable. It was crafted into rotary-dial telephones, radios, electric guitars, appliance parts, door knobs, bangles, and more. Fibres possess high tensile strength because the chains possess strong intermolecular forces such as hydrogen bonding. Cotton fibre is made of a natural polymer called cellulose. 4) Name the fibre obtained by the chemical treatment of wood pulp (or cellulose). Thatâs why synthetic fibres are become so popular. 20) What is polyester ? 2) It is harder than other plastics.Uses: It is used to make electrical goods, combs, fountain pens, buttons, plugs and switches. → It is widely used in various industries and for making a variety of household articles. Due to this, clothes made of synthetic fibres make us feel hot and uncomfortable during summer. 10. PVC (polyvinyl chloride) is a thermoplastic and is used for making toys, chappals, etc. Board â CBSE. 14)Which of the two is a thermosetting plastic: PVC or Bakelite ? Bakelite continues to be used for wire insulation, brake pads and related automotive components, and industrial electrical-related applications. 50) State the various ways in which we can avoid the use of plastics ? Synthetic fibres are also called ……….. or ………. Multiple Choice Questions Question. 1)It is a poor conductor of heat. (ii) Take a cotton carry-bag or a jute bag while going for shopping. (i) A material which does not get decomposed by natural processes. Non-biodegradable : Polythene bags, Aluminium cans, Toothbrush, Electric switch, Frying pan handle. A plastic used for making containers and carry bags (9) 3. Ans: Nylon is a synthetic fibre. State the important properties of nylon. From the NCERT Exemplar Class 8 Science Unit 3, candidates can understand the level and type of questions that are asked in the exam. The two example of non-biodegradable materials are: Plastic and Aluminium cans. 31) Explain why, frying pan handles are made of thermosetting plastics ? 1> This plastic which once set, does not become soft on heating and cannot be moulded a second time. Nowadays, Bakelite has been replaced by more modern plastics, and may be the first plastic to achieve vintage status. Clay is a mixture of compounds. Ans: Synthetic fibres catch fire very easily. Bakelite is still manufactured, however, and is used for pot handles and jewelry. Buckets made of iron get rusted but those made of plastic are not rusted. Bakelite can be used to make old telephones, desks, radios, billard balls, lamps and clocks and many other useful household items. Melamine is used for making floor tiles, kitchenware etc. Here we give Chapter 3 all solution of Class 8. c> Like synthetic fibres, plastic is also a POLYMER. Give three uses of polyester, and explain the reason for each use. Explain why the following are made of thermosetting plastics. Another name for this compound is artificial silk (5) Down 5. Required fields are marked *. 5. Assists in creating consistent equals(Object), toString(), hashCode(), and compareTo(Object) methods. It is also used to make jewelry articles and toys. d) Bakelite is a thermoplastics plastics. Ankit was learning how to cook. Here you get easy solutions of Lakhmir Singh and Manjit Kaur Science solution Chapter 3 . Why? This is because of the following two big disadvantages of plastics are: 47) What are the various ways to save the environment from excessive plastic wastes ? CBSE Science Class 8. There more than 100 questions with answers based on Class 8 Science Chapter 3 NCERT Textbook. (d) The properties and uses of bakelite are as follows:Properties: 1) It is a good electrical insulator. It is used for making gaskets, pump packings, valves, seals etc. Required fields are marked *. A synthetic fibre classified as polyester (8) 7. 3> Uses are : making plastic bottles, jars, combs, raincoats etc. (a) Plastic bowls(b) PVC(c) Polystyrene(d) NylonAnswer:(b). They melt on heating and stick to the body of the person wearing them which causes severe burn injuries. Ans: Plastic do not react with air and water. 5. For thousands of years, humans used stone to fashion tools. Answer: (D) Bakelite. Bakelite is a phenol-formaldehyde resin. Bakelite: Bakelite is phenol formaldehyde resin with monomer chemical formula of (C 6-H 6-O.C-H 2-O). It is used for making saucepan handles. For example, Bakelite is a thermosetting plastic which is a poor conductor of heat and electricity. Due to its excellent insulating properties it is used for making switches and other electrical appliances. b> if the plastic bags thrown carelessly, the animals will eat up along with the left over food and vegetables and that plastic wastes choke the respiratory systemÂ Â or lining in their stomach. Ans: Two uses of Bakelite is. 2) It is harder than other plastics. A type of fibre obtained naturally from cocoon (4) 6. Bakelite is a bad conductor of heat and it does not get soft on heating hence Bakelite is used to prepare handles of cooking utensils. Bakelite was used to make bowling balls, phonograph records, telephone housings, cookware, and billiard balls. Why is Bakelite used for making electrical switches? ... (polyvinyl chloride) is a thermoplastic and is used for making toys, chappals, etc. 2. Differentiate between thermoplastics and thermosetting plastics. 2> Examples are : polythene and polyvinyl chloride. 18. 6)Name the fibre used for making parachutes and rock climbing ropes. A polymer used â¦ NCERT Exemplar for Class 8 Science Chapter 3 Synthetic Polyvinyl chloride is used in furniture and clothing and has recently become famous for the construction for doors and windows. Acrylic fibre is made from a chemical called âacrylonitrileâ by the process of polymerisation. Learn more about the uses of polymers at vedantu.com. Ans: Thermosetting plastics are kind of plastic which once moulded cannot moulded again by heating. (i) A meterial which gets decomposed through natural processes, such as action of bacteria. It is used for making gaskets, pump packings, valves, seals etc. Ans: The four properties of plastics are:a) Plastics are poor conductors of heat and electricity. Answer â Saucepan handles are made of thermosetting plastics because thermosetting plastics are poor conductor of heat. View Answer. Prystal was a trade name used for a type of transparent Bakelite marketed by the American Catalin Corporation in a number of different colors. Frying pan handles are made with thermosetting plastics which are resistant to fire and can tolerate heat better than other plastics. A polymer used … 4. Science Class 8- Chapter 3- Synthetic Fibres and Plastics- NCERT Exercise Solutions (Question-Answer) ... Melamine, bakelite. "The Material of a Thousand Uses" Bakelite's properties make it suitable for several uses including a molding compound, binding agent, varnish, and protective coating. Ans: Examples of natural fibres: (a) Cotton (b) Silk Examples of synthetic fibres: (a) Nylon (b) Polyester. Synthetic fibres catch fire easily. Why are plastic bottles commonly used to store chemicals in a chemistry laboratory? MCQ Questions for Class 8 Science: Ch 3 Synthetic Fibres and Plastics. (iv) Dispose plastic properly and store separately in bin at home. 6. They last much longer than any other material. (d) The properties and uses of bakelite are as follows: Properties: 1) It is a good electrical insulator. 3, Give the characteristic properties and important uses of the following:a. polythene b. polystyrene c. Teflon d. Bakelite. The use of plastics can be reduced by using bags made ofâjuteâ-orâpaperâ- instead of polythene bags. Ans: Polyester is a type of synthetic fibre. The reason is clothes made of synthetic fibres do not sufficient pores for the sweat to come out, evaporate and cool our body. The uses of rayon are:a) It is used to make curtains, table clothes, blankets, bed sheets, carpets etc.b) It is used to make apparels such as jackets, suits, etc. Why do we use melamine for making kitchenware? It is used for making electrical switches, electric plugs and plug boards, etc. 17) State the characteristics of synthetic fibres. âWood pulpâ is dissolved in an alkaline solution (sodium hydroxide solution) to form a sticky liquid called âviscoseâ. 28) What are plastics ?Â Name five commonly used articles made of plastics ? The name of two synthetic fibres are: Rayon, Nylon. Bakelite is a synthetic plastic resin first produced over a century ago, and used in thousands of applications. Uses of Bakelite : (i) It is used for making electrical switches and plugs. It is used for making gaskets, pump packings, valves, seals etc. Bakelite:It is a very hard and tough plastic.It is a poor conductor of heat and electricity. All the 20 sets of online tests are free to use again and again. In the 1920s it was widely used in knobs, dials, circuitry panels, and even cabinets for radios, and it was also employed in the electrical systems of automobiles. Your email address will not be published. These phenolic and bakelite are of Grade A quality and come in a liquid-like appearance. ... Write two uses of Bakelite ? Class 8 Science Chapter 3 MCQ with complete explanation are given below. 5. Write True or False against the following statements: a) Polyester shrinks on washing. It can be explained as follows : both the two plastics are made up of long chain molecules called polumers. His father strictly told him not to wear nylon clothes in the kitchen. The fibres are crystalline in nature and have sharp melting points. Ans.Â The characteristics of synthetic fibre are:- LONG-ANSWER QUESTIONS: Answer in about 60 words. Making electric fittings such as electric switches, Making unbreakable kitchenware (cups, plates etc). Ans: Â The various ways that we can avoid the use of plastics. 9. Uses of Class org.apache.avro.io.parsing.Symbol.Sequence. Give two examples each of natural and synthetic fibres. We should reuse the plastic containers which come with jams, pickels, oil and other pacekd food. Raw materials used in the preparation of bakelite are :-phenol and formaldehyde. A few examples of this class are nylon-66, terylene and polyacrylonitrile. (a) Cotton(b) Nylon(c) Acrylic(d) PolycotAnswer:(a), Question 4.Out of the following, which is not a natural fibre ? They melt on heating and stick to the body of the person wearing them. TwoÂ example of thermosetting plastics are : Bekalite and melamine. List the important properties of nylon that make it a useful synthetic fibre. Dr. Paustenbach used the Bakelite® simulation study as an example of how dose reconstruction could be used to cast doubt about the toxicity of an asbestos product. Use again and again was not the only one are wrinkle resistant... ( polyvinyl chloride, plastics! Electric plugs/switches/plug boards are made of thermosetting plastics are given below, whereas burning smells. 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