CBSE ADDA

   chapter 3 Synthetic Fibres and Plastics #Class_8_Science_mission A. Short answer type questions 1. Name a fibre that: (a) burns with a flame giving out smell like that of burning paper. (b) burns with a flame emitting smell of burning hair. (c) burns with a sooty flame leaving behind a black beady mass. Ans: a. cotton        b. wool           c. nylon 2. How thermoset is different from thermoplastic? Ans: Thermoset Plastics are hard and rigid. Example is Teflon, Bakelite and melamine. Thermoset plastic can be moulded to any shape only once and cannot be remoulded. Thermoplastics are soft and flexible though they are not elastic like rubber. 3. Why are plastics called polymers? Plastics are called polymers as they are made up of many small units which joined together. A substance having a single unit (molecule) structure is called a monomer (mono means single; mer means a unit). A substance made up of many (poly) units joining together is known as a polymer. 4. Wh

 chapter 3 Synthetic Fibres and Plastics #Class_8_Science_mission A. Multiple choice questions. 1. Which of these is thermoplastic in nature? (a) Teflon (b) Rayon (c) Bakelite (d) Polythene 2. To make a pan non-stick, we should get it coated with (a) Bakelite (b) Teflon (c) Rayon (d) Polythene 3. Poly wool fibre is (a) Natural (b) Synthetic (c) Monomer (d) Blended 4. The plastic that cannot be molten or moulded on giving it a shape is (a) Thermoplastic (b) Polyurethane (c) Thermoset (d) Acrylic 5. Raw material for rayon comes from (a) Cellulose (b) Coal (c) Petroleum (d) Animal bones Ans:     1. d       2. b       3. b       4. c       5. c B. Match the following: Column A Answer Column B 1. Rayon 2. Teflon 3. Acrylic 4. Polycot 5. Polyurethane 6. Polystyrene 1. c       2. d       3. e       4. f        5. b       6. a a. Thermocol b. Mattresses c. Dress material d. Non-stick cookware li

Science mission class 8 solutions chapter 1  Chapter 01 Crop production and Management Questions answer Part 03 B. Long answer type questions. 1. How and why did humans start practicing agriculture? Ans: Man was basically a food gatherer. At times when the weather got rough, he and his family had to eat stale food or had to go without food. This made him to change his habit to domesticating animals and growing plants along his dwelling units. This was the beginning of farming by man. 2. How do we separate healthy seeds from a mixture of seeds? Ans: Healthy seeds are separated from the mixture of seeds by following : a. Manually by seeing the physical condition of the seed, damaged seeds are often broken or damaged in other ways. B. by soaking them in water, damaged seeds are not able for germination process after soaking them. 3. What is intercropping? Name a few crops cultivated as intercrops. Ans: Planting a leguminous crop in between two major crops in a field such as planting of

Science Mission Part 02 Questions answer Class 08 Book Chapter 01 Crop production and Management Theoretical Questions A. Short answer type questions. 1. Differentiate between the following: i. Compost and green manure Compost: Compost is the decomposed plant and animal waste which may include waste food, excreta, dried leaves and other organic matter. It is made in a compost pit using microbes. Green Manure: The green leguminous plants with their root nodules is ploughed along with the soil. The green plants and the root nodules left in the soil decompose to form green manure. ii. Compost and fertilizers Compost is a manure prepared by a biological decomposition of organic waste. It takes longer period to absorbed by plants. It is lack of nitrogen, Phosphorous and potash Fertilizer is manure prepared in factories from chemicals (mineral). It is easily absorbed by soil. It is rich in nitrogen, Phosphorous and potash iii. Pesticides and weedicides Pesticides are substances that are mea

 SChand Publication Book Science Mission Question Answer Part 01 Chapter 01 Crop production and Management Class 08 Chapter 01 Crop production and Management A. Multiple choice questions. 1. To control and destroy pests, we use   (a) Fertilizers (b) Grazing animals (c) Pesticides (d) Weedicides 2. Weeds are (a) Microbes (b) Unwanted herbs  (c) Insects (d) Fungal pests 3. Rabi crops include (a) Wheat (b) Paddy(c) Corn (maize)(d) Melons 4. Raising both, plant crop and livestock in farm is (a) Mixed farming (b) Intercropping (c) Mixed cropping  (d) Rotation of crops 5. Bins, silos and granaries are used to store  (a) Vegetables (b) Grains (c) Fruits  (d) Bulbs (onion) Ans: 1. c           2. b       3. a       4. a      5. b B. Match the following. Column 'A' Ans Column 'B' 1. Maize crop 2. Wheat crop 3. Trifolium crop 4. Blue-green alga 5. Nitrification 6. Denitrification 1. c 2. b 3. e 4. f 5. a

 Chater 04- Metals and Non Metals Question answer Part 02 Science Mission Book Class 8 Theoretical Questions Answer     JSUNIL TUTORIAL A . Short answer type questions. 1. Give reasons for the following: (a) Phosphorus is stored under water. Ans: Phosphorous is highly reactive with oxygen and catches fire when exposed to air so it is stored in water. (b) Sodium metal is stored under kerosene. Ans:  Sodium combines very quickly with the oxygen in the air and water even at a low temperature; hence it is stored in kerosene. (c) Graphite is used in dry cells. Ans:  Graphite used as electrodes in cells and batteries because it is good conductor of electricity and it does not react with other chemicals. (d) Electric wires are made from aluminium and copper. Ans:  This is because aluminium and copper are ductile and good conductor. (e) Soft iron nail kept in the solution of copper sulphate gets coated with copper. Ans:  Iron from the nails displaces copper from the copper sulphate solution, t