Advertisements
Advertisements
Question
Answer the following:
Explain the role of latent heat in the change of state of a substance.
Solution
When a solid is heated, initially, its temperature increases. Here, the heat absorbed by the body (substance) is used in increasing the kinetic energy of the particles (atomic, molecules, etc.) of the body as well as for doing work against the forces of attraction between them. As the heating is continued, at a certain temperature (melting point), solid is converted into liquid. In this case, the amount of heat energy absorbed at constant temperature by unit mass of a solid to convert into liquid phase is called the specific latent heat of fusion.
When a liquid is converted into the gaseous phase (gaseous state), at the boiling point, the heat absorbed is used for breaking the bonds between the atoms or molecules. This heat is called the latent heat of vaporization. Some solids, under certain conditions, are directly transformed into the gaseous phase. Here, the heat is absorbed, but the temperature remains constant. The absorbed heat is used for breaking the bonds between atoms or molecules. This heat is called the latent heat of sublimation.
In general, latent heat is the heat absorbed or given out by a substance during a change of state at a constant temperature.
In transformations from liquid to solid, gas to liquid and gas to solid, latent heat is given out by the body (substance).
APPEARS IN
RELATED QUESTIONS
Which has more heat: 1 g ice at 0℃ or 1g water 0℃? Give reason.
- Which requires more heat: 1 g ice at 0℃ or 1 g water at 0℃ to raise its temperature to 10℃?
- Explain your answer in part (a).
The specific latent heat of fusion of water is ______.
Calculate the total amount of heat energy required to convert 100 g of ice at −10℃ completely into water at 100℃. Specific heat capacity of ice = 2.1 J g-1 K-1, specific heat capacity of water = 4.2 J g-1K-1, specific latent heat of ice = 336 J g-1.
When a liquid is getting converted into solid, the latent heat is ………………………………
Explain the meaning of the term latent heat. State its S. I. unit.
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.
Why does evaporation causes cooling and why is water used in hot water bottles?
What do you understand by the ‘latent heat of vaporization’ of a substance?
Derive an expression for the amount of heat given out or taken up, when its temperature falls or rises by t°C.
What observation you will record and how will you determine the specific latent heat of fusion of ice?
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.
When ice is converted into water : constant temperature : : before the water evaporates : _______
Write scientific reason.
Use a pressure cooker to cook food in cold air.
Give some practical applications of specific latent heat of ice.
2875 J of heat is required to melt 115 g of lead at its melting point. Calculate the specific latent heat capacity of fusion of lead.
20 g of ice at 0°C absorbs 10,920 J of heat energy to melt and change to water at 50°C. Calculate the specific latent heat of fusion of ice. Specific heat capacity of water is 4200 J kg-1 K-1.
