Do you think rayon when burnt will stick to the body like other synthetic fibres? All plastics have one common property−what is it? Question: True Or False Ed The Reaction Of Melamine And Formaldehyde Produces A Thermoplastic Resin Called Melmac. The four properties of plastics are: 1. 5) HDPE is a tough plastic used for making toys. ... when ice melts, covalent bonds within water molecules are breaking-- true or false. Rayon is obtained by chemical treatment of wood pulp. Which of the following is not a common property of plastics? To understand the chapter in a better and easy way students are advised to solve NCERT exemplar Class 8 Science Chapter 3 synthetic fibres and plastics. Answer: (A) Both assertion and reason are true and the reason is the correct explanation of assertion. (a) polythene Hence plastic does not form rust. (iv) Most of the plastics are biodegradable. HIPS ? The molecular structures of synthetic fibres and plastics have one common feature. Bakelite is a thermosetting phenol formaldehyde resin. Properties: PET or Polyethylene tetra thalate is lightweight and it is used in making kitchen containers. Unscramble the jumbled words given below, related to synthetic materials. Rohit took with him some nylon ropes when he was going for rock climbing. 3) Polyesters are used to make bottles, utensils and wires as they are light weight and elastic. 3) Plastics are inert to air and water. branched. b. Polyester. Ankit was learning how to cook. Acrylic, polyethylene and polystyrene are thermoplastic. Rayon, a synthetic fibre, is also called artificial silk. 6. Name one thermosetting plastic which is a good insulator and is used to make plugs and switches. Why are plastic bottles commonly used to store chemicals in a chemistry laboratory? Polystyrene without plasticizers is amorphous transparent and brittle a true or from PHYS 1015 at University of South Africa. In the first part, the students will learn about synthetic fibres, its types and characteristics. 17. (d) all of these True (e) False The correct statement should be: Acrylic is a synthetic fibre that can be used instead of wool. In option b) there is cotton which is from a plant source. False. Natural materials that are used to manufacture human-made materials are known as raw materials. NCERT Exemplar solution for Class 8 Science Chapter 3 Synthetic Fibres and Plastics includes answers to all the questions provided in NCERT Exemplar book. Properties: (a) bakelite They are non-corrosive, therefore we can store chemicals in them safely. (iii) The first fully synthetic fibre was Nylon. Polypropylene is suitable for use with foodstuffs, potable and ultra pure waters, as well as within the pharmaceutical and chemical industries. Hence it is advised to avoid the use of plastic as far as possible. exothermic. The uses of polyester are as follows: FALSE; HDPE is a tough plastic used for making toys. It is also used to insulate the hollow walls of the refrigerator. Cotton fibre is almost pure cellulose that grows in a protective capsule around the seeds of cotton plants. Properties: Which of the following is a source of rayon? 8. (i) A polymer is a chain of many small units joined together which are called monomers. once they are moulded and harden on cooling, they cannot be softened again. Define a thermosetting plastic and give examples. a. PVC. Bakelite is a thermosetting plastic and is used for making electrical switches, handles of various utensils, etc. But clay is not a polymer because polymers are made up of monomer units while clay is not made up of monomer units. Give two examples each of natural and synthetic fibres. (a) rayon Page No 45: They do not absorb sweat or water and they stick to the body, which makes them uncomfortable to wear in hot humid conditions. Bakelite and polythene are both plastics. Examples of synthetic fibres: Match items in List A with the items of list B. Repeat the same activity with threads of wool, polyester, silk and nylon. 1) Nylon fibre is very strong and elastic. 2. PVC is a thermoplastic. 23. Plastics cause soil pollution and air pollution on burning. Explain how this strengthening occurs. Why? Answer: False. Plastics are very useful materials. They are non-corrosive and therefore plastic bottles are used in chemical laboratories to store chemicals. All plastics are made of long chain molecules called __________. 3. (i) A polymer is a chain of many small units joined together which are called ______. List three steps you can take to reduce the danger that plastics pose to the environment. Highly filled thermoplastic circuit board (LuVo Board / Heger Board) Manufacturing process: extrusion . Nylon is a thermoplastic silky material that can be melt-processed into fibers, films, or shapes. (b) cotton (d) The properties and uses of bakelite are as follows: True or false? ... Answer: False. 1) Nylon Lady prefers acrylic blanket over wool blankets because acrylic blankets are cheap, light in weight, more durable and are available in a variety of colours and designs. Answer 26. (b) PVC Like polypropylene, polyethylene is a _______________ thermoplastic polymer, which means it becomes pliable and moldable above a specific temperature and can be remolded multiple times. The most common source for the synthetic fibres is petroleum. Automotive Technology: A Systems … Uses: The following three steps can be taken to reduce the danger that plastics pose to the environment: Burning of plastic releases toxic gases which pollutes the air. Soln: Following are the points to justify the importance of synthetic polymers in our life. (v) A plastic used for making crockery is ______. softening and hardening can be repeated again and again. Examples are cellulose, polythene etc. Can you tell why he selected nylon ropes instead of ropes made of cotton or jute? 2. His father strictly told him not to wear nylon clothes in the kitchen. (a) Bakelite (b) Melamine (c) PVC (d) All of these. Polythene is a thermoplastic polymer consisting of long hydrocarbon chains. (b) cotton (c) The properties and uses of teflon are as follows: 26. Teflon is used to make non-stick pans. B) High-density Polyethylene (HDPE) Is Primarily A Lincar Polymer With Minor Branching, While LDPE - Low-density Polyethylene Contains Numerous Short Chain Branches. It is a blended fabric, but rayon, nylon and acrylic are not. Burning cotton smells like burning paper, whereas burning wool smells like burning hair. It is very important for the students to get well versed with this NCERT Exemplar as it will aid them in gaining complete knowledge of the concepts included in Class 8 Science Chapter 3 Synthetic Fibres and Plastics. PVC (polyvinyl chloride) is a thermoplastic and is used for making toys, chappals, etc. Therefore, they can cause severe burn injuries. A polymer is a chain of many small units joined together which are called monomers. Bakelite, a thermosetting plastic, is used to make plugs and switches. Thermosetting plastics are bad conductors of heat and electricity. What name is given to natural materials that are used to manufacture human-made materials? Which of these can you use as a substitute for glass in windows? The assertion is true but the reason is false. 16. Answer . Rayon is obtained by chemical treatment of wood pulp. Polypropylene is also crystalline and thermoplastic but is harder than polyethylene. Plastic bags contaminate food because of the poisonous dyes associated with them. 3. Plastic is a synthetic material made from a wide range of organic polymers such as polyethylene, PVC, nylon etc., that can be moulded into shape while soft, and then set into a rigid or slightly elastic form. Answer: True. Plastic is used for making a large variety of articles of daily use and these articles are very attractive. (b) polythene Polythene is a thermoplastic polymer consisting of long hydrocarbon chains. What is the significance of the prefix 'poly' in 'polyester'? 4. 1. 1) They are easier to dye in various colours. You will also love the ad-free experience on Meritnation’s Living Science 2019 2020 Solutions. Take a cotton thread of about 60 cm length. Can you write the major difference between these two types of plastics? Question 4. (b) polythene (a) rayon They cannot be decomposed by the microorganisms in the soil. (ii) Synthetic fibres do not melt on heating. Cotton smells like burning paper because both cotton and paper are extracted from plants and constitute mainly cellulose, whereas burning wool smells like burning hair because both wool and hair are extracted from animals and both have sulphur in them. These solutions for Synthetic Fibres And Plastics are extremely popular among Class 8 students for Science Synthetic Fibres And Plastics Solutions come handy for quickly completing your homework and preparing for exams. Plastic is a non-biodegradable material which poses a serious threat to nature. (c) nylon Question 27. Thermoplastic polymers can be repeatedly heated and moulded into any desired shape. Plastics are insoluble in water. 5. They do not allow electricity to pass through, which is why they are used to make plugs and switches. Write the importance of synthetic polymers in our life. Which of the following represents the correct match for items in Column A with those in Column B. 20. Plastic is a bad conductor of electricity. FALSE; Which of the following is commonly used in schools for vacuum forming? What is the difference? Why is it called artificial silk? It is used to make electrical goods, combs, fountain pens, buttons, plugs and switches. Its molecules may consist of from 50,000 to 200,000 monomers. an alcohol and carboxylic acid react to form an ester in this kind of reaction. (v) A plastic used for making crockery is melamine. 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. Synthetic fibres catch fire very easily. … 8. 13. (c) formica Clay is a 'plastic' material. Rayon is cheaper than silk and can be woven like silk. Despite being very useful it is advised to restrict the use of plastic. It is used for the packaging of delicate materials like electronic items. Bake lite is poor conductor of electricity. Nylons are man-made polymer fibres. 4) Plastics easily melt on heating and therefore they can be moulded into different shapes. 1. 4. (a) rayon (c) inflammable Cords of electrical appliances and cables also have plastic coating. Which synthetic fibre is also called artificial silk? Which of the following is a thermoplastic? ? 24. True. It is very easy to make moulds from plastic hence it is available in all possible shapes and sizes. Moreover, burning of plastics releases poisonous fumes, which causes air pollution. Therefore, these type of clothes are not suitable in a kitchen. Polyethylene, one of the most widely produced plastic in the world, is a thermoplastic polymer that has a variable crystalline structure. Disposing of plastic waste is the biggest problem we face to regret the use of plastics. They can be easily washed at home. Plastics It is used to store food item, water, milk, pickles, dry food, etc. 2) Polyester. Wool is obtained from sheep and certain other animals. Question 15. 3. Uses: The fibres are then spun into yarns and woven into clothes. 29. Why then is there concern today about their increasing use? This is because teflon is a very slippery material. 6. False. Thermoplastic polymers can be repeatedly heated and moulded into any desired shape. Question 26. Recycling of plastic is more costly than its manufacturing. 19. 2. (b) The properties and uses of polystyrene are as follows: To form rust it should react with water and oxygen. 3) Epoxy resin is a thermoplastic? c. HIPS. The terms thermoplastic and thermoset stand for how a material is or can be processed under a changed temperature. 2) Clothes made from rayon are very comfortable in summer because they can absorb sweat from the body. Why is it so? Acrylic It is used for sweaters, tracksuits, linings for boots and gloves and In furnishing fabrics and carpets. Rayon is called artificial silk because it is produced from naturally occurring polymers and looks like silk. 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