Topic Menu

Cyber-chess a chess instruction site

Specific Heat Capacity and Latent Heat Questions - GCSE standard

Q17.

(a) Andy investigated how the temperature of a lump of ice varied as the ice was heated.

He recorded the temperature until the ice melted and then the water produced boiled.

The sketch graph below shows Andy’s results.

The power output of the heater was constant.

(i) The specific heat capacity of ice is less than the specific heat capacity of water. Explain how the sketch graph shows this.

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

[2 marks]

(ii) The specific latent heat of fusion of ice is less than the specific latent heat of vaporisation of water.

Explain how the sketch graph shows this.

It took less time to melt the ice to water than it did to boil the water away to steam. As the output of energy was constant that means more enegy was required to change the state of solid to liquid than liquid to gas.

[2 marks]

(b) Nick did the same investigation and recorded the temperature until the water produced boiled.

In the Nick's investigation more thermal energy was transferred to the surroundings.

Describe two ways the results of Nick's experiment would differ from those shown in Andy's sketch graph.

Any two from:

ice/water would take more time to increase in temperature (gradients would be less steep)

ice/water would take more time to change state (horizontal lines would be longer)

the change in temperature with time would not be linear

[2 marks]

(c) When the water was boiling, 30 g of water turned into steam.

The energy transferred to the water was 69 kJ.

Calculate the specific latent heat of vaporisation of water.

30 g = 30 x 10-3 kg

69 kJ = 69 x 103 J

Energy = mass x specific latent heat of vapourisation

E = m l

l = E/m

l = 69 x 103/(30 x 10-3)

l = 2.3 x 106 J/kg

[5 marks]

(11 marks total)