Advertisements
Advertisements
Question
Why do we feel much comfortable when we sit under a moving fan especially when our body is sweating?
Solution
The reason is that sweat from our body evaporates faster under a moving fan due to rapid movement of air and so a cooling sensation is caused which makes us more comfortable.
APPEARS IN
RELATED QUESTIONS
Explain the following:
The heat supplied to a substance during it change of state, does not cause any rise in its temperature.
A molten metal of mass 150 g is kept at its melting point 800℃. When it is allowed to freeze at the same temperature, it gives out 75,000 J of heat energy.
- What is the specific latent heat of the metal?
- If the specific heat capacity of metal is 200 J kg-1 K-1, how much additional heat energy will the metal give out in cooling to -50℃?
A refrigerator converts 100g of water at 20℃ to ice at – 10℃ in 73.5 min. Calculate the average rate of heat extraction in watt. The specific heat capacity of water is 4.2 J kg-1 K-1, specific latent heat of ice is 336 J g-1 and the specific heat capacity of ice is 2.1 J kg-1 K-1.
Answer the following:
Explain the role of latent heat in the change of state of a substance.
Explain the meaning of the term latent heat. State its S. I. unit.
When 1 g of ice at 0 °C melts to form 1 g of water at 0 °C then, is the latent heat absorbed by the ice or given out by it?
Give one consequence of the high specific latent heat of fusion of ice.
Define the term ‘specific latent heat of fusion’ of a substance.
The specific latent heat of vaporisation of steam is 2260 J/g. Comment on this.
Explain the meaning of greenhouse effect.
1 kg of water is contained in a 1.25 kW kettle. Assuming specific heat capacity of water = 4.2 J/g °C and specific latent heat of vaporization = 2260 J/g, calculate:
(i) the time taken for the temperature of water to rise from 25°C to its boiling point,
(ii) the mass of water which evaporates per minute from the boiling water.
During reheating, ice is converted to water at a temperature of 0 °C.
Write scientific reason.
Even if boiling water is constantly heated, its temperature does not rise.
Define specific latent heat capacity
Specific latent heat L = ______.
Calculate the amount of heat required to convert 200g of ice at 0°C into the water at 0°C Specific latent heat of fusion of ice = 336 Jg-1
Calculate the total amount of heat energy required to melt 200 g of ice at 0°C to water at 100°C. (Specific latent heat of ice = 336 Jg-1, specific heat capacity of water = 4.2 Jg-1 °C-1)
The amount of heat energy required to melt a given mass of a substance at its melting point without any rise in its temperature is called as the ______.