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.
Figure 17 shows the student’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 Figure 17 shows this.
[2 marks]
ANSWER
The gradient is steeper for ice than water. So less energy is required to increase temperature by 1
ii- The specific latent heat of fusion of ice is less than the specific latent heat of vaporisation of water.
Explain how Figure 17 shows this.
[2 marks]
ANSWER
Water took a much longer time to vapourise than fusion of ice which means, it took more energy to go from liquid to gas than solid to liquid.
iii- A second student did the same investigation and recorded the temperature until the water produced boiled.
In the second student’s investigation more thermal energy was transferred to the surroundings.
Describe two ways the results of the experiment in Figure 17 would have been different.
[2 marks]
ANSWER
Gradients of lines will be less steeper for ice and water.
The horizontal lines will be longer as more energy required to change state
(Since more energy is wasted to the surrounding so it will take more time for temperature to increase of ice and water. And longer to change their states. As a result, the change in temperature is expected to be not linear.)
iv- When the water was boiling, 0.030 kg of water turned into steam.
The energy transferred to the water was 69 kJ.
Calculate the specific latent heat of vaporisation of water.
Give the unit.
[5 marks]
SOLUTION
Using the latent heat of vaporisation formula from equation sheet.
