The melting point of Lauric acid is about 45° Celsius. The freezing point is about 45° Celsius. They are the same because they involve phase changes between the same two phases (liquid and solid). The only difference is that heat is being added to reach the melting point, and heat is being removed to reach the freezing point. So they are the same, only in different directions. I determined the freezing and melting points, because on the graphs, the line plateaued at about 45° Celsius. This means that during that time period (roughly one and a half minutes) the Lauric acid was changing states of matter.
On the heating curve, when the substance is in either state of matter, (liquid of solid) the kinetic energy, or temperature of the Lauric acid is increasing. This is because the substance is heating up and the molecules that it is composed are beginning to move faster. The potential energy is at a constant because the substance is not changing phases of matter during this time. This is similar for the cooling curve, only instead of increasing, the kinetic energy (temperature) is decreasing, because as heat is being taken away, the molecules are slowing down. The amount of potential energy is increasing when the Lauric acid is melting, and decreasing when it is freezing. There is more potential energy in a liquid than in a solid, so as it is changing phases of matter, the potential energy is also changing.
Enrichment: The actual melting/ freezing point of Lauric acid is 43.2° Celsius. My results were slightly off because I was only calculating the temperature every fifteen seconds. If i were to record it every second, then the data may have been more accurate. My percent error was 4.17%.
Lauric acid is used to help scientists learn the molar mass of unknown substances. They mix the unknown substance with the Lauric acid and calculate the temperature at which the mixture freezes. The chemical formula is C12.
Source: http://en.wikipedia.org/wiki/Lauric_acid
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