Specific Latent Heat

As we mentioned phase change from last post, today we are going to talk about the measurement of thermal energy that takes for a substance to undergo phase change -- specific latent heat.

Take the example from last time, if an ice cube has been dropped into a container of water, its temperature will not change for awhile once it reaches zero degree Celsius. However, we know that heat is constantly transferring between water and ice, so where did all the thermal energy go? The answer is changing phase!

As we all know, ice melts once its temperature reaches zero. When it starts to melt, the thermal energy from the water starts to break down the hydrogen bonds between molecules in the ice. By doing so, ice could change its phase and become water. The amount of thermal energy for ice to change phase can be calculated by using specific latent heat. Specific latent heat is the amount of heat required for 1 kg of material to change phase, which represented by the letter L. The relationship between required thermal energy (L) and latent heat is shown in the following equation:

Q = m (L)

Something interesting that we learned today is that liquid takes more thermal energy than solid to change phase. However, I still have the following questions: does latent heat of a substance change if it has been put into a metal container and a wood container? If ice is cold enough, can it turn water that has the same amount as it into ice? What is the phase after gas?