CBSE Guess > Papers > Question Papers > Class X > 2009 > Science > Science

Q. 19. What is meant by renewable natural resources? 1

Ans. The sources of energy which are being produced continuously by nature and are inexhaustible are called renewable sources of energy. For example: Hydel energy, Wind energy, Solar energy, Biomass energy etc.

Q. 20. Write the name and functions of any two parts of the human hind brain. 2

Ans. Pons, Cerebellum and Medulla are the parts of hind brain

• The pons take part in regulating respiration.

• Cerebellum helps to maintain posture and balance of the body.

Q. 21. What is reproduction? What are its two types? Which one of the two confers new characteristics on the offsprings and how? 2.

Ans. The production of new organisms from the existing organisms of the same species is known as reproduction.
There are two main methods of reproduction:
(i) asexual reproduction
(ii) sexual reproduction
The sexual reproduction confers new characteristics on the offsprings because the offspring receives some genes from the mother and some from the father and the mix of genes of mother and father in various different combinations causes genetic variation.

Q. 22. In a solar cooker, the following arrangements are made. Write one function of each arrangement.
(a) The box is made of insulating material such as plastic or wood.
(b) The inner walls of the box are painted black.
(c) The box is covered with a transparent glass sheet.
(d) A plane mirror is hinged at an angle at the top of the box. 2

Ans. (a) The box is made of insulating material such as plastic or wood so that the heat absorbed by the cooker does not radiate out.
(b) The inner walls of the box are painted black because a black surface absorbs the maximum amount of heat from sunlight. It maximizes absorption of heat and minimises heat loss due to reflection.
(c) The box is covered with a transparent glass sheet because a glass sheet traps more and more heat rays of the sun and does not allow the heat to go back due to green house effect.
(d) A plane mirror is hinged at an angle at the top of the box so as to increase the area over which solar energy is collected, as the plane mirror reflects all the rays falling on its surface into the solar cooker
box.

Q. 23. Draw a schematic diagram of a biogas plant and label on it the following: (a) Digester (b) Gas tank 2

Ans.

Q. 24. What are biodegradable and non-biodegradable substances? Select two biodegradable pollutants from the following: 2
Agricultural waste, glass, plastic, sewage, DDT

Ans. Those materials which can be broken down to non-poisonous substances in nature in due course of time by the action of micro-organisms like certain bacteria, are called biodegradable substances.

Those materials which can not be broken down into non-poisonous or harmless substances in nature are called non-biodegradable substances. Two biodegradable pollutants are Agricultural waste and sewage.

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