The first image is the classic heating curve. You will notice there are five distinct areas to the graph. A graph based on real data is unlikely to look this smooth, but the shape should be the same.

We have plotted the energy that has been transferred to the ice (through the pathway heating by particles) on the x-axis. If the object was heated up by plugging it into an electric heater, or by putting it on top of a Bunsen burner, then the energy will increase linearly with time. Therefore, you will get the same shape graph if you had plotted time along the x-axis. This is the second graph.

It is usually easy to heat up an object in a school science lab at a reasonably constant rate (using a heater or a Bunsen burner). You can cool an object too, but this is usually not at a constant rate, because an object will cool more rapidly at the start when the temperature difference is greatest. The third graph shows a cooling curve.