Thermal Physics 3

A solid substance is placed in a boiling tube and heated steadily. The temperature - time graph of the substance is as shown below. At which labelled point would the substance be a mixture of liquid and gas?

• A

• B

• C

• D

During the process of melting,

• the melting substance gains thermal energy and therefore increase its temperature.

• the melting substance changes from a liquid to a solid.

• there is no transfer of thermal energy and therefore the temperature of the substance remains constant.

• the intermolecular forces between the molecules of the substance becomes weaker.

When steel increases its temperature,

• the size of the molecules increases.

• the mass of the molecules increases.

• the molecules vibrate at higher speed.

• the density of each molecules decreases.

Which of the following statements is/are correct?

(1) Heat is defined as the energy which is transferred from one place to another due to a temperature difference between them.

(2) Heat will flow from one body of higher energy level to another of lower energy level.

(3) When an object has higher temperature, its internal energy is higher than another object of lower temperature.

• (1)

• (1) and (3)

• (2)

• (2) and (3)

What is the meaning of 400 J/(kg ^oC)?

• 400 J of energy is needed to raise the temperature of an object.

• 400 J of energy is needed to raise the temperature of an object by 1 ^oC.

• 400 J of energy is needed to raise 1 kg of an object by 1 ^oC.

• 400 J of energy is needed to raise the mass of an object by 1 kg.

A 2 kg copper object is heated from 30 ^oC to 35 ^oC. How much increase in thermal energy is required, given that the specific heat capacity of copper is 400 J/(kg ^oC)?

• 40 J

• 160 J

• 1000 J

• 4000 J

4000 J of energy is used to heat up a 5 kg copper block from an initial temperature of 20 ^oC. What is the final temperature of the copper block, given that the specific heat capacity of copper is 400 J/(kg ^oC)?

• 22 ^oC

• 25 ^oC

• 30 ^oC

• 40 ^oC

In an experiment to find the specific heat capacity of copper, a 5 kg block of copper is being heated by a heater rated "240 V, 5 A" for a period of 3 minutes. Given that the temperature of the copper block increases from 20 ^oC to 120 ^oC and assuming that there is no heat is lost to the surrounding, what is the specific heat capacity of copper?

• 380 J/(kg ^oC)

• 400 J/(kg ^oC)

• 432 J/(kg ^oC)

• 453 J/(kg ^oC)

How much thermal energy is required to melt 2 kg of ice completely at 0 ^oC? (Specific latent heat of fusion of ice = 336 000 J kg^-1)

• 0 J

• 168 000 J

• 336 000 J

• 672 000 J

The specific latent heat of fusion of ice = 336 000 J kg-1. What is the meaning of 336 000 J kg-1?

• 336 000 J of energy is needed to raise the temperature of an object.

• 336 000 J of energy is needed to raise the temperature of an object by 1 ^oC.

• 336 000 J of energy is needed to melt 1 kg of ice to 1 kg of water at its melting point.

• 336 000 J of energy is needed to heat 1 kg of ice to 1 kg of steam at its boiling point.