Latent Heat of Fusion

Q.

Differentiate between-

Melting point and freezing point.

Q.

Find the amount of heat in calories required to convert 10g of ice at –10°C to water at 10°C

[C of ice = 0.5 cal/g°C, C of water = 4.2J/g°C = 1 cal/g°C, L of ice = 80cal/g]

1. 95 J

2. 950 calories

3. 100 J

4. 1000 calories

Q.

Why do mixtures never possess a fixed melting point or a fixed boiling point? Give reason.

Q.

A solids changes to a liquid on heating. Why?

Q.

What happens when ice is melted?

Q.

The meaning of the following statement is:

The specific heat capacity of copper is 0.4 J g^{-1 o}C^-1.

1. This means 0.4 J of heat energy is required to melt 1 g of copper

2. This means 0.4 J of heat energy is required to raise the temperature of 1 g of copper by 1^o C

3. This means 0.4 J of heat energy is required to raise the temperature of any mass of copper by 1^o C

4. This means 0.4 J of heat energy is required to raise the temperature of 1 g of copper by 10^o C

Q.

Why is latent heat hidden?

Q.

A block of ice at -$10{}^{\circ }C$ is slowly heated and converted to steam at $100{}^{\circ }C$. Which of the following curves represents the phenomenon correctly?

1. 

2. 

3. 

4. 

Q. Identify the correct value for the latent heat of fusion of ice.

1. 150 kJ/kg
2. 220 kJ/kg
3. 336 kJ/kg
4. 580 kJ/kg

Q.

Is latent heat positive or negative?

Q.

The process of changing gas to a liquid by cooling, is called ____________.

Q.

How much heat is needed to melt $15kg$ of ice at $0^{°}C$?

Q.

Explain the factors affecting

(a) melting point

(b) boiling point

(c) evaporation

Q.

Can latent heat become zero?

Q. Select the region in the graph that specifies latent heat of fusion.

1. 
2. 
3. 
4. 

Q.

What is difference between sensible heat and latent heat?

Q.

Which among the following expands on melting?

1. Lead

2. Wax

3. Ice

4. Copper

Q.

Define the latent heat of a substance.

Q. The graph shown in the figure represents change in the temperature of $5kg$ of a substance with time, as it absorbs heat at a constant rate of $42kJ$ $mi{n}^{-1}$. The latent heat of vapourization of the substance is:

1. $630kJk{g}^{-1}$
2. $126kJk{g}^{-1}$
3. $84kJk{g}^{-1}$
4. $12.6kJk{g}^{-1}$

Q.

How do the molecules jiggle when an object is heated?

Q. The graph shown in the figure represents change in the temperature of $5kg$ of a substance with time, as it absorbs heat at a constant rate of $42kJ$ $mi{n}^{-1}$. What would be the latent heat of vapourization of the substance?

1. $630kJk{g}^{-1}$
2. $126kJk{g}^{-1}$
3. $84kJk{g}^{-1}$
4. $12.6kJk{g}^{-1}$

Q. What is the specific latent heat of fusion of ice in CGS system?

1. $100$ calories per gram
2. $80$ calories per gram
3. $85$ calories per gram
4. $110$ calories per gram

Q.

Identify whether the statement is true or false:

The heat which can be seen easily is called latent heat.

1. True
2. False

Q.

An immersion heater of power $20W$ just keeps $200g$ of solid metal at its melting point. The heater is switched ON and temperature starts raising after $4min$, then the specific latent heat of fusion of the metal is ________.

1. $24J{g}^{-1}$

2. $24cal{g}^{-1}$

3. $24calk{g}^{-1}$

4. $24Jk{g}^{-1}$

Q.

What is meant by heat?

Q. When the ice in the frozen lake starts melting then the temperature of surrounding ___________. Complete the sentence

1. Increases
2. Decreases
3. Remains same
4. None

Q.

Latent heat comes into the picture only when there is a change of state.

1. True

2. False

Q.

When the solid changes into a liquid, there is no change in:

1. Temperature

2. Average kinetic energy of the molecules

3. Both A and B

4. Average distance between the molecules

Q.

What is specifc heat?

1. The amount of heat required to raise the temperature of 5kg of a substance by 1°C.

2. The amount of heat required to burn a substance.

3. The amount of heat that should be removed to reduce the temperature of 5kg of a substance by 1°C.

4. Amount of heat required to raise the temperature of unit mass of a substance by 1°C.

Q. Specific latent heat of ice by electrical method is given by the formula if $P=$ Power, $m$= mass and $t$=time

1. $Ptm$
2. $Pt/m$
3. $Pm/t$
4. $P/mt$