Topic 3 Thermal Physics: Quiz 2 Modelling a Gas

Question 1

The graph shows the distribution of speeds for the molecules of a gas at a particular temperature.
Which statement is correct?

Accepted Answer

D The peak value of the graph would move to the right if the temperature is increased.

Answer

A All the molecules have the same kinetic energy.

Answer

B The commonest value of speed is also the average speed.

Answer

C The graph shows that the molecules of a gas are widely spaced apart.

Question 2

A gas is enclosed inside a cylinder which is fitted with a frictionless piston.
Initially, the gas has a volume V1 and is in equilibrium with an external pressure p. The gas is then heated slowly so that it expands, pushing the piston back until the volume of the gas has increased to V2.
How much work is done by the gas during this expansion?

Accepted Answer

A p(V2 –V1)

Answer

B 1/2.p(V2 –V1)

Answer

C p(V2 +V1)

Answer

D 1/2.p(V2 +V1)

Question 3

If the Universe was such that the speed of the molecules in a substance increased with temperature but at any particular temperature the speed of all the molecules in a substance was the same, which process would not occur?

Accepted Answer

C evaporation

Answer

A boiling

Answer

B condensation

Answer

D melting

Question 4

Which process does  not  require energy to be supplied?

Accepted Answer

C freezing

Answer

A boiling

Answer

B evaporation

Answer

D melting

Question 5

A gas is enclosed in a container of fixed volume. It gains heat energy from an external source. 
What happens to the molecules of the gas?

Accepted Answer

B They move faster inside the container.

Answer

A They expand.

Answer

C They move further apart.

Answer

D They vibrate with greater frequency.

Question 6

A hot liquid is allowed to cool. The graph shows the cooling curve. 
In which part of the curve is latent heat released?

Accepted Answer

B QR

Answer

A PQ

Answer

C RS

Answer

D ST

Question 7

The	molar mass of magnesium	 is 24 g. 12 g	of magnesium contains the same number of particles as:

Accepted Answer

A. 6	 g of	 carbon-12.

Answer

B. 12 g of carbon-12.

Answer

C. 24 g of carbon-12.

Answer

D. 6.02 × 10^23 g of carbon-12.

Question 8

A fixed mass  of an ideal gas is	at temperature T.	 The	 pressure is doubled and the volume is halved.		
What is the temperature after these changes?

Accepted Answer

B T

Answer

A. T/2

Answer

C 2T

Answer

D 4T

Question 9

Ice at –10 °C is heated at a constant rate until it is water at +10 °C.
Which graph shows how the temperature changes with time?

Accepted Answer

C

Answer

A

Answer

B

Answer

D

Question 10

Which of the following is NOT an ideal gas assumption?

Accepted Answer

C Molecules exert forces on each other even when not in contact

Answer

A Molecules move with a range of speeds

Answer

B The volume of the molecules is negligible compared with the volume of the gas itself

Answer

D The collisions of the molecules with each other and the container walls are elastic.

Question 11

At regular intervals along a railway line there is a gap between the rail sections. 
What is the reason for the gap between the rail sections?

Accepted Answer

A to allow for expansion of the rail sections during hot weather

Answer

B to allow for vibrations of the rail sections as the train passes over them

Answer

C to allow rain water to drain from the rail sections

Answer

D to keep the wheels of the train and carriages on the rail sections

Question 12

Ice is taken from a freezer and left in a room. The ice melts and eventually the water reaches room temperature. 
Which energy transfers take place?

Accepted Answer

C

Answer

A

Answer

B

Answer

D

Question 13

Some air is trapped inside a small balloon. The average kinetic energy of the air molecules in the balloon is increased. 
What remains the same?

Accepted Answer

B the mass of the air in the balloon

Answer

A the density of the air in the balloon

Answer

C the temperature of the air in the balloon

Answer

D the volume of the air in the balloon

Question 14

A clinical thermometer is designed to respond quickly to a change in temperature and to have a high sensitivity.
Which design features should the clinical thermometer have?

Accepted Answer

C Bulb: thin glass; Bore: narrow

Answer

A Bulb: thick glass; Bore: narrow

Answer

B Bulb: thick glass; Bore: wide

Answer

D Bulb: thin glass; Bore: wide

Question 15

The energy required to change liquid water into water vapour at the same temperature is called latent heat of vaporisation.
What does this energy do?

Accepted Answer

A increases the average separation of the water molecules

Answer

B increases the average speed of the water molecules

Answer

C raises the temperature of the air near the water

Answer

D splits the water molecules into their separate atoms

Question 16

A 2  kW kettle containing boiling water is placed on a balance. It is left there and continues to boil for 5 minutes. The balance reading changes by 0.2   kg. 
What does this information give as a value for the specific latent heat of vaporisation of water?