Latent Heat of Vaporization

Q.

What is the relationship between Boiling point and Vapour pressure ?

Q.

What is the value of latent heat of vapourisation of water?

Q.

Why is alcohol used as a thermometric liquid in certain situations? Give two reasons.

Q.

Why there is no change in temperature during the melting of a solid?

Q.

What is the temperature of boiling water?

1. $212°F$

2. $273K$

3. $99°C$

4. $120°F$

Q.

Why do we feel comfortable while sitting under a moving fan in summer?

Q.

Which of the following causes more severe burns?

1. Steam

2. Boiling water

3. Steam and boiling water.

4. Cold water

Q.

Why are we able to sip hot tea faster from saucer rather than from a cup?

Q. During summer, water kept in an earthen pot becomes cool because of which phenomenon?

Q.

The process due to which a liquid changes into a gaseous state at a constant temperature by releasing heat energy is known as boiling or vaporisation.

1. True

2. False

Q.

Explain the role of latent heat in the change of state of a substance.

Q.

In the determination of boiling of water, it is advised to put the bulb of the thermometer above water rather than in water. Why?

Q.

The latent heat of vaporization of a substance is always greater than its latent heat of sublimation.

1. Greater than its latent heat of fusion

2. Greater than its latent heat of sublimation

Q.

Define absolute temperature.

Q.

The latent heat of vaporization of steam is more than that of the boiling water. Explain

Q.

A substance is in the form of a solid at 0 °C. The amount of heat added to this substance and the temperature of the substance are plotted on the graph.

Fig, 11.9 Amount of heat (in Joule)

If the specific heat capacity of the solid substance is 500 J/kg °C, find from the graph; the specific Latent heat of fusion of the substance in the liquid state.

1. 30000 J kg^-1

2. 50000 J kg^-1

3. 20000 J kg^-1

4. 40000 J kg^-1

Q.

Steam burns are more painful than the boils formed with boiling water because

1. Water at 100°C has 2268 J of heat more than Steam contains at 100°C

2. Steam at 100°C has 2268 J of heat more than water contains at 100°C

3. Steam has more heat capacity than water

4. Water has more heat capacity than Steam

Q.

What do you understand by the term solidification point or freezing point of a liquid?

Q. When the SVP(saturation vapour pressure) equals the atmospheric pressure, the process is called ?

1. Boiling
2. sublimation
3. Vaporization
4. Evaporation

Q.

The molar heat capacity of water at constant pressure P is $75{\mathrm{JK}}^{-1}{\mathrm{mol}}^{-1}$. When $1.0\mathrm{kJ}$of heat is supplied to $100\mathrm{g}$ of water which is free to expand, the increase in temperature of the water is:

Q.

State True or False:

Thermal expansion occurs only in gases.

1. True

2. False

Q.

$40g$ of ice at $-10°\mathrm{C}$ is heated by a heater of power $250\mathrm{W}$, such that water formed from it, attains the temperature equal to the boiling point of water. For how long is the heater switched on? [S.H.C. of ice$=2{\mathrm{Jg}}^{-1}{\mathrm{C}}^{-1}$; Sp. latent heat of ice$=340{\mathrm{Jg}}^{-1}$]

Q. A substance changes from its solid state to the liquid state when heat is supplied to it. Name the process.

Q. Question 4
During summer, water kept in an earthen pot becomes cool because of the phenomenon of
(a) diffusion
(b) transpiration
(c) osmosis
(d) evaporation

Q.

List some effects of heat on matter?

Q.

Boiling water causes more severe burn than water vapour at 100 degree celcius.

1. Steam

2. Boiling water

Q.

Calculate the amount of ice which is required to cool 150 g of water contained in a vessel of mass 100 g at 30°C, such that the final temperature of the mixture is 5^oC. Take specific heat capacity of material of vessel as 0.4 J g^{-1 o}C^-1 ; specific latent heat of fusion of ice = 336 J g^-1 ; specific heat capacity of water = 4.2 J g^-1 °C^-1.

1. 34.35 g

2. 55.65 g

3. 46.92 g

4. 56.52 g

Q.

Define latent heat of vaporization.

Q.

Increase in humidity is one of the factor which increases the rate of evaporation.

1. True

2. False

Q. Steam causes more severe burns than boiling water at the same temperature