 The simplest way to break the hydrogen bond is by imposing some thermal energy, but it is expensive. We know that when we heat an object, we tend to increase its temperature, but that's not always the case. Sometimes you can apply heat to an object. That heat, that thermal energy goes into rearranging the molecular structure, which is otherwise known as a change of phase. This occurs for water when you change its phase from solid water, which is ice, to liquid water, and then also from liquid water to water vapour into its gas phase. Here we have a simple experiment that demonstrates the change of phase of water. We start out by placing a dish containing ice onto a burner and watching it with a thermal camera where the colour indicates the temperature. This purple-blackish colour is below zero Celsius and this white colour is above 100 Celsius. The ice is initially below zero Celsius, which we can see by its dark colour. As the dish of ice begins to warm, some of the water changes phase from solid to liquid and we can see the convective circulation of the liquid water and the temperature of this liquid water is increasing. Solid water, however, remains at zero Celsius, even though it is completely surrounded by much warmer liquid water. The size of the solid water decreases as the ice melts, but the temperature of the ice does not increase. That is, the heat that we are pumping into the ice is not changing its temperature, but it is leading to an internal rearrangement of the molecular structure and it's changing the phase of water from solid to liquid.