Science P6 MBS 2018 SA1 Q21

Four identical pots made of different materials, W, X, Y and Z, were filled with the same amount of water and placed over a flame. The temperature of the water was measured until they started boiling.The results are shown in the graph below.Arrange the materials W, X, Y and Z in the correct order from the best conductor of heat at the top, to the poorest conductor of heat at the bottom.