The correct statement should be: (d) they become soft again and again on reheating. (a) Annealing is the process by which glass is cooled and made tougher. As saucepans are used for cooking, their handles should be able to sustain large amount of heat without melting. Which of the following is a polyester fibre? (e) The odd one is ester. polymer, blended fibre. We have provided Synthetic Fibres and Plastics Class 8 Science MCQs Questions with Answers to help students understand the concept very well. Thermoset are useful in high temperature applications since they do not soften like a thermoplastic. (d) Thermoplastics are easy to mould and they can regain their shape. (a) Annealing is the process by which glass is cooled and made tougher. Dusters made of cotton (natural fibre) are good for use in kitchen. Choose the thermoplastic and thermosetting plastic from the following: Melamine, PVC, polythene, nylon, Bakelite. Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Nylon, rayon, acrylic, terene and polycot are synthetic fibres. These polymers possess intermolecular forces of attraction intermediate between elastomers and fibres. (a) sand, sodium bicarbonate, limestone When the small piece of fibre from the sweater was burnt by Anu, it smelled like burning plastic. (c) It is a naturally occurring fibre obtained from wood. (c) Polymers are large molecules made by joining many small molecules. The correct statement should be: Soln: Answer is (a) Melamine. These fibres have mixed properties of both the fibres involved in its production. Thermoplastic polymers These are the linear or slightly branched long chain molecules capable of repeatedly softening on heating and hardening on cooling. (a) rayon (b) False The plastics which when moulded once, cannot be softened by heating are called thermosetting plastics. (d) Polyester fibres are obtained from petroleum products. Bakelite is a very poor conductor of heat and electricity and it is used for making electrical switches. Chain Growth Polymerisation or Addition Polymerisation It involves formation of reactive intermediate such as free radical, a carbocation or a carbanion. Polycot, a blended fibre is made from Thermosetting plastics become soft only the first time; when they are reheated, they become hard (take firm shape). (b) they can be moulded into any shape (c) polythene 2. Synthetic condensation polymers have a wide array of household, industrial, commercial, and medical uses … (b) Hydrogen chloride gas is given off when PVC is burnt. The plastics which gets deformed easily on heating and can be bent easily are called thermoplastics. (d) True As wood contains huge amount of cellulose, rayon (synthetic fibre) is prepared chemically from wood pulp (cellulose). Three properties of synthetic fabrics are as follows: (c) man-made materials and plastics. Polythene, polystyrene, PVC, melamine and formica are plastics. (c) they do not conduct heat or electricity Plastics are used to cover electrical cables because _____________. The word polymer is coined from two Greek words poly means many and mer means unit. Thermoplastic: Plastics that can be deformed easily upon heating and can be bent easily. For example, polythene and PVC are thermoplastics. (d) they can coloured by adding pigments. They are also insulators of heat and electricity. (c) polyester and acrylic. (b) polyester fibres and objects made of glass. Are these statements true or false? We provide a total manufacturing solution that covers planning, molding, decorating and processing. When plastics are burnt, they release hydrogen chloride gas. We can sort the given fabrics into natural, synthetic and blended fibres as shown in the table below: Find the odd one out in the following. Once processed and cured, they are infusible and cannot be re-melted or dissolved. Plastics are not biodegradable and take thousands of years to degenerate. 3. It resembles wool but does not shrink or wrinkle. Ans: Two uses of Bakelite is. Bakelite is a thermosetting plastic which is a poor conductor of heat and electricity. MCQ Questions for Class 8 Science with Answers (d) cotton, jute, silk, rayon All questions and answers from the Active Science Book of Class 8 Science Chapter 3 are provided here for you for free. Without any doubt, that quality as well makes melamine a perfect material for decorative objects. Thermoplastic type material can be recycled and reusable, while the runner or material waste for thermosetting plastic type cannot. Plastic - Thermoplastic and thermosetting plastic | Bakelite | Melamine. (a) Thermosetting plastics remain hard on reheating and can sustain high temperatures. (c) The odd one is acrylic. Bakelite® molding compounds are engineering thermosets (ETS) not engineering thermoplastics (ETP). (a) synthetic fibres and plastics You will also love the ad-free experience on Meritnation’s Active Science Solutions. (e) False Linear polymers and a combination of linear and cross-linked polymers come under thermoplastics. Ans: Two uses of melamine is : Making floor-tiles 3. Soln: Answer is (b) Rayon. (f) Rayon, which is obtained from cellulose, is a natural fibre. It is a thermoplastic, while bakelite, melamine and formica are thermosetting plastics. (d) sand, sodium carbonate, calcium carbonate. They become soft only the first time; they become hard. It is a thermoplastic, while bakelite, melamine and formica are thermosetting plastics. Blended fabrics contain both synthetic and natural fibres. (e) Terylene, a synthetic fibre, can be used instead of wool. The key difference between thermoplastic and thermoset is that thermoplastic can be melted into any shape and re-used whereas thermosets have a permanent shape and cannot be recycled into new forms of plastic.. Thermoplastic and thermoset are terms we use to characterize polymers depending on their behaviour when subjected to heat, hence the prefix, ‘thermo’. As the containers used for microwave cooking should be able to sustain reheating without causing any damage to the food kept in them, these containers can be made of thermosetting plastics. One characteristic of thermosets is that ___________. (a) The odd one is teflon. These are used in the manufacturing of toys, combs and different types of containers. (c) large molecules made by joining many small molecules together Choose the thermoplastics and thermosetting plastics from the following: Melamine, Polythene, Bakelite, Polyvinyl chloride. They absorb less water and they dry easily. The overuse of plastics leads to many problems like environmental pollution, health hazards, etc. They absorb very less water. Rayon is prepared chemically from wood pulp (cellulose). Some examples are bakelite, melamine, formica, etc. Henry Ford made his own deadly version of Bakelite by mixing phenol, formaldehyde and defatted soybean meal which reacted to create a thermoplastic resin that could be molded under pressure to create durable nonstructural plastic parts, such as radio knobs, light switch pulls, distributor caps, body trim, etc. (a) they become soft on cooling High quality cp9000 Thermoplastic Resin Powder , Phenol Formaldehyde Novolac For Composite Material from China, China's leading Phenol Formaldehyde Resin product market, With strict quality control Phenol Formaldehyde Resin factories, Producing high quality cp9000 Thermoplastic Resin Powder , Phenol Formaldehyde Novolac For Composite Material products. Ans: Thermosetting plastics are kind of plastic which once moulded cannot moulded again by heating. (c) dacron, acrylic, terene, terylene It is used to make electrical switches and handles of utensils. This results in environmental pollution. Kerala Plus Two Chemistry Notes Chapter 15 Polymers. (e) Blended fabrics are made by the combination of natural and synthetic fibres. (c) cashmere (f) Polyester fibres like dacron and terene are made from petroleum products. It is used to make floor tiles, kitchenware and fire resistant fabrics. 5. Give two examples of thermosetting plastics. It is a monomer (small molecule) unit, while polyester, cotton and nylon are polymers (larger molecules made up of smaller monomer units). View NCERT Solutions for all chapters of Class 8, FREE Downloadable NCERT Solutions.Works without internet. For example, Bakelite is a thermosetting plastic which is a poor conductor of heat and electricity. (d) PVC. (d) All the statements are correct. (d) sand, sodium carbonate, calcium carbonate Which of the following is a thermosetting plastic? Such plastics are called thermosetting plastic. (b) terylene 1. ended fabrics contain both synthetic and natural fibres. Like bakelite and Perspex, the objects made of melamine can have polished and shiny surfaces which can be achieved by molding or treating objects with very fine abrasives. (b) Blended fabrics contain only synthetic fibres. Choose the thermoplastics and thermosetting plastics from the following: Melamine, Polythene, Bakelite, Polyvinyl chloride. Bakelite & Melamine Injection Molding Machine, Model: LCH-H80 toLCH-H500 ; LCH-V100 to LCH-V850, There are two types of injection features: the thermoplastic type and thermosetting plastic type. (a) bakelite, teflon, formica, melamine It is a thermoplastic, while bakelite, melamine and formica are thermosetting plastics. All Active Science Solutions for class Class 8 Science are prepared by experts and are 100% accurate. (b) Thermoplastics are not used for making saucepan handles. Acrylic is a synthetic fibre, which is light, soft and warm. (a) synthetic fibres and plastics. Plastic is a very generalized term for polymers that can mean either a thermosetting or a thermoplastic Plastic. (c) Dusters made of nylon or other synthetic materials are good for use in the kitchen. Rayon looks like silk. (a) the process by which glass is cooled and made tougher This is the key to their strength, toughness and durability. Therefore, thermoplastics are not used for making saucepan handles. Anu bought a sweater which was not very expensive. (b) It is obtained from wood containing large amount of cellulose. (a) melamine It is a polymer (synthetic fibre) made up of small chemical molecules called esters. Recycling of plastics is very costly. Define the following: 1 Answer +1 vote . (a) It resembles wool in appearance. Making electric fittings such as electric switches, Making plugs and sockets. Melamine is a thermoseting plastic which is resistant to fire and can tolerate heat better than other plastics. The correct statement should be: (b) polyester and wool. Ans: The full form of PVC is ‘ Polyvinyl chloride’ PVC is a thermoplastic. (c) Bakelite is used to make plugs and sockets. Polymers are large molecules formed by the linkage of smaller molecules called monomers. Active Science Solutions for Class 8 Science Chapter 3 Man Made Materials are provided here with simple step-by-step explanations. They cannot be moulded more than once as they take a firm shape once they are heated and cooled. polythene, polystyrene, nylon, PVC, rayon, terene, acrylic, formica, polycot, melamine Fuji Bakelite is a plastics manufacturer that offers a balance of technology and art. 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