Phase Change

Q.

What is the boiling point of milk?

Q.

Describe various effects of heat on matter.

Q. When ice melts into water at $0^{\circ }\text{C}$, its volume will

1. remain the same
2. increase significantly
3. decrease
4. increase slightly

Q.

The diagram below shows the change of phases of a substance on a temperature-time graph on heating the substances at a constant rate.

(a) What do the parts AB, BC, CD and DE represent?

(b) What is the melting point of the substance?

(c) What is the boiling point of the substance?

Q. The phenomenon of a liquid changing into vapour at a temperature below its boiling point, is called:

1. Condensation
2. Sublimation
3. Boiling
4. Evaporation

Q. During the phase change of a pure substance, the temperature of the substance ______.

1. increases abruptly
2. decreases linearly
3. remains constant
4. decreases abruptly

Q.

For a pure substance, boiling point and condensation point are the same.

1. True

2. False

Q.

Can the Latent heat be negative?

Q.

The latent heat of fusion of solid water at $0^{\circ }$ is $80cal/g$. How much heat is required to convert $4g$ of ice at $0^{\circ }$C to water at $0^{\circ }$C ?

1. $20cal$

2. $160cal$

3. $80cal$

4. $320cal$

Q.

State four effects which heat energy can bring about in matter.

Q.

Why does temperature remain the same during melting till all the ice has changed to water ?

Q.

Assertion (A) : Ethanoic acid is also known as glacial acetic acid.

Reason (R) : The melting point of pure ethanoic acid is 290 K and hence it often freezes during winters in cold climates.

1. Both (A) and (R) are true and (R) is correct explanation of the assertion.

2. Both (A) and (R) are true but (R) is not the correct explanation of the assertion.

3. (A) is true but (R) is false

4. (A) is false but (R) is true.

Q.

1 kg of ice at $0^{o}C$ is heated at a constant rate and its temperature is recorded after every 30 s till steam is formed at ${100}^{o}C$. Draw a temperature-time graph to represent the change of phases.

Q.

(a) What do you understand by the change of phase of a substance?

(b) Is there any change in temperature during the change of phase?

(c) Does the substance absorb or liberate any heat energy during the change of phase?

Q.

How is the volume of water affected when it boils at ${100}^{o}C$ ?

Q.

What happens to the kinetic energy of the particles of a solid when heat is supplied to the solid at its melting point.

1. The kinetic energy of the particles remains constant

2. The kinetic energy of the particles decreases

3. The kinetic energy of the particles increases

4. None of these

Q.

In which of the three physical states, the constituent particle have maximum kinetic energy?

Q.

The specific latent heat of fusion of lead is 5.9 kcalkg^-1. A block of lead at its melting point needs 177 kcal of heat for complete melting. What is the mass of the lead?

1. 60 kg

2. 30 kg

3. 35 kg

4. 6 kg

Q.

What is the normal freezing point?

Q.

How would you perform an activity to find out the effect of a change in temperature?

Q.

Which among these contract on melting?

1. Lead

2. Wax

3. Ice

4. Iron

Q.

The process of conversion of liquid to vapour at any temperature is called:

1. Evaporation

2. Sublimation

3. Condensation

4. Boiling

Q. The constant temperature at which solid changes to a liquid is called as ___ point.

1. boiling
2. melting
3. freezing
4. vaporization

Q.

Why are vegetables cooked with difficulty at a hill station?

1. Boiling point increases as we go up on hilly areas
2. Boiling point increases because atmospheric pressure is low
3. There is no change in boiling point
4. Boiling point decreases as we go up on hilly areas

Q.

In a closed container of constant volume, the pressure of water exhibits an interesting dependence on temperature -

The point D (273.16 K, 0.006 atm) is called the triple point, Tp, of water, where all there phases coexist. What is the observed phase change when the temperature is increased from -10⁰C to +10⁰C, while maintaining a constant pressure of 0.006 atm?

1. Solid → Liquid

2. Liquid → Gas

3. Solid → Gas

4. Gas → Liquid

Q.

A screw gauge with a least count of 0.01 mm is used to measure the diameter of a lead shot. The reading on the pitch scale is found to be 1 mm and the reading on the head scale is 40 divisions. If the screw gauge has a zero error of – 0.05 mm, what is the surface area of the lead shot?

Q. Calculate the amount of heat required to convert 1.00 kg of ice at $-{10}^{\circ }$C into steam at ${100}^{\circ }$C at normal pressure. $(S_{ice}=2100Jk{g}^{-1}{K}^{-1},$
$S_{water}=4200Jk{g}^{-1}{K}^{-1},$
$L_{f,ice}=3.36\times {10}^{5}Jk{g}^{-1}$,
$L_{v,water}=2.25\times {10}^{6}Jk{g}^{-1})$

1. $6.03\times {10}^{6}J$

2. $3.03\times {10}^{6}J$

3. $4.03\times {10}^{6}J$

4. $5.03\times {10}^{6}J$

Q. A lump of ice (0.1 kg) at $-{10}^{\circ }$C is put in 0.15 kg of water at ${20}^{\circ }$C. How much water will be found in the mixture when it has reached thermal equilibrium?
$(C_{ice}=0.5kcalk{g}^{-1}{k}^{-1},L_{ice}=80kcalk{g}^{-1})$

1. 181.25 g
2. 210 g
3. 150 g
4. 31.25 g

Q.

Draw a graph by plotting temperature versus time for ice.

Q.

A vessel of negligible heat capacity contains 40 g of ice in it at 0⁰C. A metal of mass 50 g at 50⁰C is placed into the ice to melt it. The final temperature of the contents of the vessel is 10⁰C. Find the specific capacity of the metal.

(Specific latent heat of fusion of ice = 336 J/g and Specific heat capacity of water = 4.2 J/g⁰C)

1. 756 kJ/kgºC

2. 756 J/gºC

3. 7.56 J/gºC

4. 7.56 kJ/gºC