5 What type of graph would you suggest they use and why? 6 Draw the graph that Freda and Paul would have drawn.
Freda and Paul’s teacher then asked them to comment on the shape of the graph they had just drawn.
7 List as many things as possible about the shape of the graph you have just drawn.
Freda and Paul noted that on their graph there were horizontal parts at 0 °C and another at 100 °C.
8 Can you suggest what the heat energy being supplied by the Bunsen burner is being used for at these two temperatures?
After discussion, Freda and Paul spoke to their teacher about their findings. She explained to them that what they observed was a type of heat called latent heat. Latent heat is heat that causes a change of state and not a change in temperature.
When heat is applied by the Bunsen burner, the temperature usually rises. However, when heat causes a change in state (solid to liquid or liquid to gas) and not a change in temperature it is latent heat. It is the heat needed to turn a solid to a liquid and a liquid to a gas.
The word ‘latent’ comes from Latin latēns, meaning ‘lying hidden’. ‘Latent’
Freda and Paul wanted to carry out the investigation again using another substance in order to see if this hypothesis held true for all substances.
9 How would Freda and Paul make sure that this was a fair comparison with the results they got for water?
Freda and Paul’s teacher suggested that they use a substance called lauric acid. This is a solid at room temperature. Here are the results collected by Freda and Paul for the lauric acid:
