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KV CRPF AVADI CHENNAI 65 SCIENCE CLASS 7 HOLIDAY HOME WORK 24-12-2015 I. Fill up :- 1. Souring of milk is a _______________ change Ans :- Chemical 2. When carbondioxide is passed through line water it turns milky due to the formation of _________________. Ans :- Calcium Carbonate 3. Changes in which new substances are formed are called _____________ change. Ans :- Chemical 4. The chemical name of baking soda is __________________ Ans :- Sodium hydrogen carbonate. 25-12-2015 II. Choose the correct answer :- 1. Which of the following is not a chemical change a) burning of coal b) digestion of food c) melting of ice d) rusting of iron Ans :- Melting of ice. 2. Anaerobic bacteria digest animal waste and produce biogas (change - A). The biogas is then burnt as fuel (change - B). The following statement pertain to these changes choose the correct one. a) Process - A is a chemical change b) Process - B is a chemical change c) Both process A and B are chemical changes d) Non of these processes is a chemical change Ans :- Both process A and B are chemical changes 3. The layer of rust is actually deposit of a) Iron (III) oxide b) Mud c) Water d) oxygen Ans :- Iron (III) oxide 4. The process of depositing a layer of zinc on iron is called. a) crystallisation b) galvanisation c) rusting d) melting Ans :- Galvanisation. 26-12-2015 III. Question and answer :- 1. Explain why rusting of iron object is faster in coastal areas than in desert. And :- Coastal areas contains many salts. The salt water makes rust formation faster. 2. How would you show that setting of curd is a chemical change? Ans :- Conversion of milk into curd is a permanent and irreversible lead to produce new substance with different composition and properties. 27-12-2015 IV. Fill in the blanks :- 1. In addition to the rock particles the soil contain _____________ Ans:- Mineral, organic matter, air and water. 2. The water holding capacity is the highest in _____ Ans:- loamy soil 3. Clayey and loamy soil are suitable for cereals like ______________ Ans :- Wheat and grams 4. Each layer of soil is called a ____________ Ans :- horizon 5. The mixture of rock particles and humus is called _________ Ans :- Soil 28-12-2015 V. Answer the following :- 1. List two difference between clayey soil sandy soil. Ans :Clayey Soil 1. It has good water holding - It Sandy Soil has poor water holding capacity 2. It has less percolation rate of water 2. capacity - It has more percolation rate of water Explain how soil pollution could be prerented. Ans :Prerention of soil pollution 3. 1. Recycle waste 2. Dispose off sewage property 3. Use organic manure What is humus? Ans :- Dark colored partially decayed organic matter rich in nutrient. It makes soil porous. 4. Explain how soil is formed. Ans :- Big and heavy rocke broken into smaller pieces by action of wind and climate - Small particles get decomposed on exposure to air. - Decomposed Vegetable and animals mix with soil 29-12-2015 VI. Fill int the blanks :- 1. In cockroaches, air enters the body through ____________ Ans :- Spiracles. 2. What are stomata? Ans : - Stomata are tiny pores presention the surface of leaf. 3. During heavy exercise, leg gets cramp due to ________ Ans :- Lactic acid 4. What is aerobic Respiration? Ans :- Repiration occurs in the presence of oxygen - harge amount of energy is released - Food molecules are brokendown into water and carbondioxide. 30-12-15 1. Name the organs of breathing in fish. Ans:- Gills. 2. What is anaerobic respiration. Ans:- It occurs in the absence of oxygen - Small amount of energy is released. - Food molecular are broken down into ethyl alcohol and carbondioxide 31-12-15 1. Why do we offers sneez when we inhale a lot of dust - laden air? Ans :- We sneez to get rid of anwanted particles lid dust from our body. It allows only clean and dust free air 2. Name the skeletal structure surrounding the chest cavity. Ans :- Rib cage. 1-1-16 1. Name the muscular floor of the chest cavity. Ans :- Diaphragm 2. Which procen of respiration releases more energy. Ans :- Aerobic respiration 2-1-16 1. Write the similarities between aerobic and anaerobic respiration? Ans :- Both aerobic and anaerobic respiration produce energy and give out cabondioxide. 2. Which of the follosing does not have lungs for breathing ? (a) lizard (b) froq Ans :- Fish END (c) fish (d) fox