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Matter In Our Surroundings
Define the term energy. Give some examples of bodies possessing some energy.
The energy of a body is measured by it's capacity to do certain amount of work. A body does work, implies more energy has been expended.
Some examples of bodies possesing energy are:
(i) When a fast moving cricket ball hits a stationary wicket, it throws away the wicket. The moving ball possesses energy and hence does work on the wicket.
(ii) A hammer raised through a certain height possesses energy. When it falls on a nail placed on a piece of wood, it drives the nail into the wood.
(iii) When a child winds a toy car and place it on the floor, the toy car begins to move. On winding the toy car gains energy and does work in moving against the force of friction.
In the examples given above, different means of doing work is acquired by the object. Hence, these objects are said to posses energy.
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Give reason for the following observations.
We can get the smell of perfume sitting several metres away.
What is the physical state of water at
a) 25°C
b)00C
c)1000C
What is the physical state of water at
0°C
What is the physical state of water at
100°C
Give two reasons to justify
Water at room temperature is a liquid.
Give two reasons to justify
An iron almirah is a solid at room temperature.
Why is ice at 273K more effective in cooling than water at the same temperature ?
What produces more severe burns, boiling water or steam ?
8. Name A, B, C, D, E and F in the following diagram showing state change :
Both boiling and evaporation convert a liquid into vapour. What is the difference between the two process
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