We will investigate thermodynamics, the study of heat transfer, in detail in Unit 6. However, we need to introduce some thermodynamics terminology here to understand how phase changes occur. We can define the specific heat of a substance as the energy it takes to raise 1 g of a substance by 1 degree Celsius. The unit used for heat is the joule (J), or kilojoule (kJ). We define heat of fusion as the energy or heat necessary to change a given amount of a substance (often one mole) from solid to liquid. Heat of fusion uses the unit of J or kJ. Heat of vaporization is the amount of heat needed to change a given amount of a substance (often one mole) from liquid to gas, with the unit of J or kJ.
Watch these three videos in order. Our first video uses the heating curve of water to define specific heat, heat of fusion, and heat of vaporization.
Source: Khan Academy, https://youtu.be/nRswZfgsh2c
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