This hydrogen chloride gas gets combined with the moisture in the environment to form hydrochloric acid, which is toxic and can cause problems to the human body. (c) they do not conduct heat or electricity (d) polyester and cotton. It is not a polyester synthetic fibre, while dacron, terene and terylene are polyester synthetic fibres that are manufactured from petroleum products. Three properties of synthetic fabrics are as follows: (a) Melamine (b) Polythene (c) PVC (d) Nylon. 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 (d) they can coloured by adding pigments. Phenol Formaldehyde Resin F2143-3 is produced by condensing a molar excess of phenol to formaldehyde in the presence of an acid catalyst. 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. The correct statement should be: Plastics are used to cover electrical cables because _____________. Therefore, thermoplastics are not used for making saucepan handles. It is a monomer (small molecule) unit, while polyester, cotton and nylon are polymers (larger molecules made up of smaller monomer units). (b) silicon, sodium bicarbonate, limestone (b) Hydrogen chloride gas is given off when PVC is burnt. Choose the thermoplastics and thermosetting plastics from the following: Melamine, Polythene, Bakelite, Polyvinyl chloride. What is the sweater most likely made of? (c) Dusters made of nylon or other synthetic materials are good for use in the kitchen. (a) synthetic fibres and plastics. It is used to make floor tiles, kitchenware and fire resistant fabrics. Types of Polymerisation 1. giving reasons. Give scientific reasons for the following: Phenol Formaldehyde Resin Powder Heat Resistance for Brake Pads Product description . Explanation: Thermosetting plastics when moulded once can not be softened by heating. 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(c) Polymers are large molecules made by joining many small molecules. They can be moulded into different shapes again and again. Which of the following statements is true for rayon? (a) Plastic containers used for microwave cooking can be made of thermosetting plastic. They absorb water and do not catch fire easily. (a) rayon It is used to make electrical switches and handles of utensils. 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. These solutions for Man Made Materials are extremely popular among Class 8 students for Science Man Made Materials Solutions come handy for quickly completing your homework and preparing for exams. 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. Even though biodegradable plastics have been developed by scientists, they are costly and are not used on a large scale. Choose the thermoplastic and thermosetting plastic from the following: Melamine, PVC, polythene, nylon, Bakelite. Thermoplastic type material can be recycled and reusable, while the runner or material waste for thermosetting plastic type cannot. As plugs and sockets may get heated up while they are being used, Bakelite, a thermosetting plastic, is used for making them. All Active Science Solutions for class Class 8 Science are prepared by experts and are 100% accurate. (a) Thermosetting plastics remain hard on reheating and can sustain high temperatures. Even if they catch fire, they do not stick to the body of the person who is holding it. All questions and answers from the Active Science Book of Class 8 Science Chapter 3 are provided here for you for free. (d) Thermoplastics are easy to mould and they can regain their shape. Thus, the sweater was not pure wool, but it was made of synthetic acrylic fibre. (d) True Thermoplastic is a type of a polymer which can be easily melted by providing heat in order to recycle the material. (d) Polyester fibres are obtained from petroleum products. Polymers are large molecules formed by the linkage of smaller molecules called monomers. For example, cotton is a naturally occurring polymer that is made up of glucose as monomer units. 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. Melamine and Bakelite are thermosetting plastics. (f) two fabrics made from petroleum products. Linear polymers and a combination of linear and cross-linked polymers come under thermoplastics. It is used in electric switches, plugs, handles of pressure cooker and tea kettle, radio and TV cabinets, etc Bakelite, Melamine, etc are some examples of it. (a) Polymers are small molecules made by stringing together several monomers. (c) silicon, sodium carbonate, calcium carbonate synthetic fibers and plastics; class-8; Share It On Facebook Twitter Email. (a) they become soft on cooling They are produced by the combination of synthetic fibres and natural fibres. Some common thermoplastics are polythene, polystyrene, polyvinyls, etc. (c) It is a naturally occurring fibre obtained from wood. 3. 2. 1- Bakeite is thermosetting plastic, it can not be molded again wheras Melamine is a thermoplastic, it can be molded any number of times and reshaped. The correct statement should be: (c) polythene They absorb less water and they dry easily. For example, polycot is obtained by blending cotton with polyester. Polythene, polystyrene, PVC, melamine and formica are plastics. Which of the following is a thermosetting plastic? 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. It is a polymer (synthetic fibre) made up of small chemical molecules called esters. As plugs and sockets may get heated up while they are being used, Bakelite, a thermosetting plastic, is used for making them. Recycling of Plastic. Anu bought a sweater which was not very expensive. (a) melamine Bakelite is used for making electrical switches whereas melamine is used for floor tiles. It resembles wool but does not shrink or wrinkle. Thermoplastic: Plastics that can be deformed easily upon heating and can be bent easily. Without any doubt, that quality as well makes melamine a perfect material for decorative objects. Bakelite® molding compounds are engineering thermosets (ETS) not engineering thermoplastics (ETP). (d) they become soft again and again on reheating. (e) Blended fabrics are made by the combination of natural and synthetic fibres. Making electric fittings such as electric switches, Making plugs and sockets. (e) fabrics made by the combination of natural and synthetic fibres (d) synthetic fibres and thermoplastics. In 1927 the Bakelite patent expired. Ans: Thermosetting plastics are kind of plastic which once moulded cannot moulded again by heating. (a) polyester and nylon. You will also love the ad-free experience on Meritnation’s Active Science Solutions. Synthetic condensation polymers have a wide array of household, industrial, commercial, and medical uses … Rayon, which is obtained from cellulose, is a synthetic fibre. 3- Bakelite is a synthetic plastic and Melamine is … 40) State two uses of melamine ? View NCERT Solutions for all chapters of Class 8, FREE Downloadable NCERT Solutions.Works without internet. The correct statement should be: (a) It resembles wool in appearance. We provide a total manufacturing solution that covers planning, molding, decorating and processing. It is a blended fabric, but rayon, nylon and acrylic are not. Plastics are not biodegradable and take thousands of years to degenerate. The word polymer is coined from two Greek words poly means many and mer means unit. Dusters made of cotton (natural fibre) are good for use in kitchen. (c) Bakelite is used to make plugs and sockets. Acrylic is a synthetic fibre, which is light, soft and warm. It is a blended fabric, but rayon, nylon and acrylic are not. The correct statement should be: (c) cashmere ... Few examples of thermosetting plastics are phenolic resins, epoxy resins, amino resins, melamine, Bakelite. Polythene and PVC are examples of thermoplastic. Define the following: 3. MCQ Questions for Class 8 Science with Answers Soln: Answer is (a) Melamine. Explanation: (a) the process by which glass is cooled and made tougher Soln: Answer is (b) Rayon. Usually, the material is thermoplastic type if the product material is plastic; the material is thermosetting type if the product is Bakelite and melamine. They dry quickly and do not require ironing. (d) polyester and cotton 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. 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. Ans: Two uses of Bakelite is. The correct statement should be: Acrylic is a synthetic fibre that can be used instead of wool. (d) acrylic. 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