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Q. 6. Name any two appliances which are based on the application of heating effect of electric current. 1

Ans. The heating effect of current is utilised in the working of electrical heating appliances such as electric iron, electric oven.

Q. 7. When magnesium ribbon burns in air or oxygen a product is formed. State the type of chemical reaction and name the product formed in the reaction. Write balanced chemical equation of this reaction. 2

Ans. When a magnesium ribbon is heated, it burns in air with dazzling white flame to form a white powder called magnesium oxide.

It is an example of a combination reaction because two elements magnesium and oxygen are combining to form a single compound magnesium oxide.

Q. 8. State Mendeleev’s periodic law. Write two achievements of Mendeleev’s periodic table. 2

Ans. See Q.4 and Q.5 (S.A.T), Chapter 5. [Page 50

Q. 9. A student sitting at the back of a class is not able to see what is written on the blackboard. He however, sees it clearly when sitting on the front seat at an approximate distance of 1·5 m from the blackboard. Draw ray diagrams to illustrate the image formation of the blackboard writing by his eye-lens when he is seated at the (i) back seat (ii) front seat. 2

Ans. See Q.11, Sample Paper I. [Page 3.

Q.10. Give reasons for the following. 2
(i) The sun appears reddish at sunrise or sunset.
(ii) The sky appears dark instead of blue to an astronaut.

Ans. (i) The Sun at the time of sunrise and sunset is more near the horizon, and near the horizon most of the blue light of shorter wavelengths is scattered away by the particles and gases of the atmosphere. Light from the Sun near the horizon passes through thick layers of air and larger distance in the Earth’s atmosphere before reaching our eyes. Therefore, the light that reaches our eyes is of longer wavelength that gives rise to the reddish appearance of the sun.
(ii) The sky appears dark instead of blue to an astronaut because there is no atmosphere containing air in the outer space to scatter sunlight.

Science 2009 Question Papers Class X
Delhi		Outside Delhi		Compartment Delhi		Outside Delhi		Foreign
	Set 1 (PDF)		Set 1 (PDF)		Set 1		Set 1		Set 1 (PDF)
					Set 2		Set 2
					Set 3		Set 3