21 May 2019
Latent Heat is the heat required for an object to change phase (melt,boil,freeze etc). In class, the melting of a cube of ice was discussed to explain latent heat, as well as the boiling of water.
The question asked in class was, what are the different temperature time graphs for the melting of ice on a metal lid vs on a plastic lid. The graph shapes were the same, but on the metal lid, the fusion of ice-water was faster since metal is a good conductor of electricity and gives heat faster to the ice to make it melt.
Fusion: When a substance changes from a solid to a liquid
When ice melts, it goes through 5 stages on a temperature time graph. The first is when the temperature of the ice increases when put on a metal surface, then when the ice turns to water, then the temperature of the water increases, then the water turns to steam, and then the phase is fully changed into steam.
Latent Heat Of Fusion: The energy required to transition one unit of a substance from solid to liquid
Latent Heat Of Vaporization: The energy required to transition one unit of a substance from liquid to vapor.
The equations to describe the different transformations and state changes are:
Q=mLf (for melting or freezing). where Q is heat required to change a sample, m is the mass of the sample, and Lf is the latent heat of fusion
Q = mLv (for vaporizing or condensing) where Q is heat required to change a sample, m is the mass of the sample, and Lf is the latent heat of vaporization
After Unit Reflection: In this unit, I demonstrated an understanding of latent heat and state transformations – such as the heat required to change states, and how the temperature changes as a piece of ice melts into water and then steam. This post also showed an understanding of energy transformations that took place as the states of the ice were changing. I also demonstrated an understanding of equations for latent heat of fusion and and latent heat of vaporization.
Energy E Blog 