Generally, you choose some convenient number for each small division of the graph to represent. Usually, 1, 2, 5, 10, and multiples of 10 times those are considered "convenient."
Here, it might do to use 5 units for each small division, so that 180 is 36 small divisions. If you have 10 small divisions per inch of your graph, then your graph will be about 4 inches high (if you start from zero).
Since the range of your graph is from 112 to 180, about 70 units, you could actually use 1 unit for each small division. Again, if you are using 10 divisions per inch, your graph will be about 7 inches high, so will fit nicely on a page. In this case, the lower edge will start at 110, not zero.
Since this is a temperature plot, you expect the curve to be exponential, with a lower limit of room temperature. Thus, you may want to use a graph with a range that includes room temperature at the low end. That will affect your choice of vertical scale somewhat.
