Since the temperature changes in a continuous way, there is meaning to the values in the intervals between the points. Therefore, the points are joined by a smooth curve.

1 2 3 4 5 130 140 150 T (°C)
t (min)

Graph of data points.

Normally on the vertical axis we would start at 0 degrees and have evenly-spaced marks at 10 degree intervals. However, the curve would look almost flat if we did that and we would not be able to see the drop in temperature very easily.