Science 2008 CBSE [ Delhi ] Set I
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What happens chemically when quick lime is added to water?Marks:1
On adding water to quick lime, slaked lime is formed with evolution of heat. The reaction takes place as follows:
How will you test for the gas which is liberated when hydrochloric acid reacts with an active metal?Marks:1
Active metal gives hydrogen gas on treating with hydrochloric acid.
On bringing the burning splinter near the mouth of the test tube from where gas is evolving, if the splinter starts burning with pop sound then it indicates the presence of hydrogen gas.
From amongst the metals sodium, calcium, aluminium, copper and magnesium, name the metal
(i) which reacts with water only on boiling, and
(ii) another which does not react even with steam. 1/2,1/2Marks:1
(i) Magnesium (Mg)
(ii) Copper (Cu)
Copy this figure in your answer book and show the direction of the light ray after reflection:
The reflected ray become parallel to principal axis:
To an astronaut why does the sky appear dark instead of blue?Marks:1
In space, scattering of light does not take place as there is no atmosphere there, hence to an astronaut sky appears dark.
The refractive index of light is 2.42. What is the meaning of this statement in relation to speed of light?Marks:1
It means that speed of light in air is 2.42 times the speed of light in the given medium.
How is the increase in demand for energy affecting our environment adversely?Marks:1
Increase in demand for energy affects our environment as more and more fossil fuels are being used to meet the increasing energy requirements. This causes increase in environmental pollution.
Name the largest cell present in the human body.Marks:1
What process in plants is known as transpiration?Marks:1
The process of loss of water in the form of water vapours through stomata is called transpiration.
List any two differences between pollination and fertilisation.Marks:2
1. It involves transfer of pollens from anther to stigma in a flower.
1. It involves fusion of male and female gametes.
2. It occurs in plants only.
2. It occurs in plants as well as in animals.