Acrylic is a synthetic fibre that can be used instead of wool. This results in environmental pollution. 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Some examples are polythene, polyvinyl chloride (PVC), polystyrene, teflon, etc. (a) melamine (c) dacron, acrylic, terene, terylene (c) man-made materials and plastics. The plastics which gets deformed easily on heating and can be bent easily are called thermoplastics. It is a thermoplastic, while bakelite, melamine and formica are thermosetting plastics. The list of materials mentioned above can be classified as We have provided Synthetic Fibres and Plastics Class 8 Science MCQs Questions with Answers to help students understand the concept very well. These are used in the manufacturing of toys, combs and different types of containers. They are produced by the combination of synthetic fibres and natural fibres. These new plastics could be used to produce household products in … Rewrite the false ones correctly. Phenol Formaldehyde Resin Powder Heat Resistance for Brake Pads Product description . 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. Bakelite® molding compounds are formulated from one of four heat-cured, crosslinkable resin Are these statements true or false? (d) polyester. The correct statement should be: It is not a polyester synthetic fibre, while dacron, terene and terylene are polyester synthetic fibres that are manufactured from petroleum products. giving reasons. For example, Bakelite is a thermosetting plastic which is a poor conductor of heat and electricity. Thermoplastic is used for making combs, toys, buckets, mugs, etc. It is because of these advantages of polyester over cotton that polyester is blended with cotton to form polycot. It is a blended fabric, but rayon, nylon and acrylic are not. Explain the difference between thermoplastics and thermosetting plastics. Bakelite and melamine are examples of thermosetting plastic. (b) False Ans: Two uses of melamine is : Making floor-tiles Name the following: Examples are bakelite and melamine. This is the key to their strength, toughness and durability. Bakelite is a thermosetting plastic, it cannot be molded again whereas Melamine, being a thermoplastic, can be molded any number of times adn reshaped. Ans: Two uses of Bakelite is. Such plastics are called thermosetting plastic. (c) polythene They are also insulators of heat and electricity. (f) Polyester fibres like dacron and terene are made from petroleum products. 3- Bakelite is a synthetic plastic and Melamine is … Ans: Thermosetting plastics are kind of plastic which once moulded cannot moulded again by heating. It is a polymer (synthetic fibre) made up of small chemical molecules called esters. They can be moulded into different shapes again and again. Sort out these fabrics into different groups: rayon, nylon, jute, acrylic, terylene, wool, silk, polyester, terry cotton, cotton. Polyesters are wrinkle-free and do not require ironing. ended fabrics contain both synthetic and natural fibres. (c) silicon, sodium carbonate, calcium carbonate (e) False (c) large molecules made by joining many small molecules together Melamine is a thermoseting plastic which is resistant to fire and can tolerate heat better than other plastics. (a) Melamine (b) Polythene (c) PVC (d) Nylon. The decorative melamine board has a structure obtained by laminating a surface layer and a core layer. (c) It is a naturally occurring fibre obtained from wood. It is used to make floor tiles, kitchenware and fire resistant fabrics. (b) Thermoplastics are not used for making saucepan handles. The overuse of plastics leads to many problems like environmental pollution, health hazards, etc. The formation process of these two types of plastics also differs. (c) The odd one is acrylic. For example, polycot is obtained by blending cotton with polyester. (a) False Dusters made of cotton (natural fibre) are good for use in kitchen. MCQ Questions for Class 8 Science with Answers Blended fabrics contain both synthetic and natural fibres. Explain why, thermoplastics become soft on heating but thermosetting plastics do not become soft on heating. for example : Bakellite , melanin, Formaldehyde Thermoplastic Plastic are kind of plastic which can be moulded again and again by heating and easily reused.For example :PVS, Polysterine , nylon , polythine Plastics are used to cover electrical cables because _____________. Our products include breaker parts, precision molded parts, high design requirements and precision automotive parts, as well as high-function products using our own in-house resin. (b) teflon Once processed and cured, they are infusible and cannot be re-melted or dissolved. It is used to make electrical switches and handles of utensils. (d) cotton, jute, silk, rayon (b) they can be moulded into any shape For example, cotton is a naturally occurring polymer that is made up of glucose as monomer units. (c) they do not conduct heat or electricity. It is a synthetic fibre, while cotton, jute and silk are natural fibres. Recycling of Plastic. Thermoplastic type material can be recycled and reusable, while the runner or material waste for thermosetting plastic type cannot. The correct statement should be: 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. (d) Thermoplastics are easy to mould and they can regain their shape. 5. 39) Write two uses of Bakelite ? As plugs and sockets may get heated up while they are being used, Bakelite, a thermosetting plastic, is used for making them. Which of the following statements is true for rayon? Bakelite, or polyoxybenzylmethyleneglycolanhydride, is an early plastic. (a) they are light Plastics are bad conductors of heat and electricity (good insulators). (a) Polymers are small molecules made by stringing together several monomers. What is the sweater most likely made of? All questions and answers from the Active Science Book of Class 8 Science Chapter 3 are provided here for you for free. Plastic - Thermoplastic and thermosetting plastic | Bakelite | Melamine. (b) polyester and wool. (d) they become soft again and again on reheating. (e) The odd one is ester. Recycling of plastics is very costly. As plugs and sockets may get heated up while they are being used, Bakelite, a thermosetting plastic, is used for making them. Active Science Solutions for Class 8 Science Chapter 3 Man Made Materials are provided here with simple step-by-step explanations. (d) Polyester fibres are obtained from petroleum products. Give scientific reasons for the following: (c) they do not conduct heat or electricity These fibres have mixed properties of both the fibres involved in its production. ... Few examples of thermosetting plastics are phenolic resins, epoxy resins, amino resins, melamine, Bakelite. Sand (silicon dioxide (SiO2), sodium carbonate (Na2CO3) and calcium carbonate (CaCO3) are the three raw materials needed to make glass. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students. Choose the thermoplastics and thermosetting plastics from the following: Melamine, Polythene, Bakelite, Polyvinyl chloride. 3. Therefore, thermoplastics are not used for making saucepan handles. It is used to make electrical switches and handles of utensils. They are produced by the combination of. Which of the following is a polyester fibre? Students are advised to practice the NCERT MCQ Questions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics with Answers Pdf free download is available here. A thermoset material as the name implies can be heated only once because an irreversible reaction occurs so that the material remains solid in what ever form it is in when the reaction takes place. It resembles wool but does not shrink or wrinkle. For example, polythene and PVC are thermoplastics. Linear polymers and a combination of linear and cross-linked polymers come under thermoplastics. (d) acrylic. Polythene and PVC are examples of thermoplastic. (c) Polymers are large molecules made by joining many small molecules. (c) cashmere Nylon, rayon, acrylic, terene and polycot are synthetic fibres. (f) False 3. (b) Blended fabrics contain only synthetic fibres. Thermosetting plastics become soft only the first time; when they are reheated, they become hard (take firm shape). Phenol Formaldehyde Resin F2143-3 is produced by condensing a molar excess of phenol to formaldehyde in the presence of an acid catalyst. (c) Thermosetting plastics remain hard even at high temperatures. Types of Polymerisation 1. Melamine is a thermosetting plastic which is resistant to fire and can tolerate heat better than other plastics. It is a thermoplastic, while bakelite, melamine and formica are thermosetting plastics. In 1927 the Bakelite patent expired. (a) melamine  In the growing consumer market of the 1930s and after, Bakelite faced competition from other thermosetting resins such as urea formaldehyde and melamine formaldehyde and from new thermoplastic resins such as cellulose acetate, polyvinyl chloride, polymethyl methacrylate, and polystyrene. (c) they can be repeatedly remoulded into desired shapes Choose the thermoplastics and thermosetting plastics from the following: Melamine, Polythene, Bakelite, Polyvinyl chloride. Example: Bakelite, melamine, etc. (a) Annealing is the process by which glass is cooled and made tougher. (e) Blended fabrics are made by the combination of natural and synthetic fibres. (d) polyester and cotton. They absorb less water and they dry easily. (b) terylene (b) they become hard after heating Usually, the material is thermoplastic type if the product material is plastic; the material is thermosetting type if the product is Bakelite and melamine. Bakelite® molding compounds are engineering thermosets (ETS) not engineering thermoplastics (ETP). As wood contains huge amount of cellulose, rayon (synthetic fibre) is prepared chemically from wood pulp (cellulose). It is a monomer (small molecule) unit, while polyester, cotton and nylon are polymers (larger molecules made up of smaller monomer units). (b) polyester fibres and objects made of glass. Kerala Plus Two Chemistry Notes Chapter 15 Polymers. As saucepans are used for cooking, their handles should be able to sustain large amount of heat without melting. Thermosetting Plastic: Some plastics do not get deformed on heating, and cannot be re-molded into a new shape. (b) Hydrogen chloride gas is given off when PVC is burnt. Which of the following is a thermosetting plastic? 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. Blended fibres are fibres that are obtained by blending natural fibres with synthetic fibres. They are also insulators of heat and electricity. (a) Thermosetting plastics remain hard on reheating and can sustain high temperatures. 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