Topic 3 - Particle Model of Matter

Question 1

A student investigated how the temperature of a lump of ice varied as the ice was heated.
The student recorded the temperature until the ice melted and then the water produced boiled.
The figure below shows the student’s results.
The power output of the heater was constant.

The specific heat capacity of ice is less than the specific heat capacity of water.
Explain how the figure above shows this. (2 marks)

Answer 1

• the gradient for ice is steeper than the gradient for water
• which means that less energy is needed to increase the temperature by a fixed amount

Question 2

A student investigated how the temperature of a lump of ice varied as the ice was heated.
The student recorded the temperature until the ice melted and then the water produced boiled.
The figure below shows the student’s results.
The power output of the heater was constant.

The specific latent heat of fusion of ice is less than the specific latent heat of vaporisation of
water.
Explain how the figure above shows this. (2 marks)

Answer 2

• water took more time to vaporise than the ice took to melt
• which means that less energy is needed to change the state from solid to liquid (than from liquid to vapour)

Question 3

When the volume of gas in the syringe increased, the pressure on the inside walls of the syringe decreased.
Explain why. (3 marks)

Answer 3

• there are less frequent collisions between the particles and the walls of the syringe
• (causing) a lower (average) force on the walls of the syringe
• (and) pressure is the total force per unit area

Question 4

The temperature of the helium in the balloon was increased.
The mass and volume of helium in the balloon remained constant.
Explain why the pressure exerted by the helium inside the balloon would increase. (4 marks)

Answer 4

• particles would have a higher (mean) kinetic energy
• (so) increased number of collisions with the walls of the balloon per second
• greater forces exerted in collisions (between particles and balloon walls)
• greater force exerted on same area

Question 5

A person is using a bicycle pump to inflate a tyre.
The internal energy of the air increases as the tyre is inflated.
Explain why. (2 marks)

Answer 5

• work is done on the air (in the tyre)
• so the temperature (of the air) increases