The graph depicting the energy change during the conversion of ice into steam is known as a heating curve or a phase diagram. It shows how the energy supplied to a substance affects its temperature and state.
Let's break down the different regions of the graph:
Solid Ice (Low Temperature, Increasing Energy): Initially, the substance is in the solid state (ice) at a low temperature. As heat is applied, the temperature of the ice rises steadily, and the energy absorbed causes the ice particles to vibrate faster.
Melting Point (Constant Temperature): Once the ice reaches its melting point (0 degrees Celsius or 32 degrees Fahrenheit at standard pressure), the temperature remains constant even though heat continues to be added. This period is known as the latent heat of fusion region. The energy supplied is used to break the intermolecular bonds holding the ice molecules together, allowing them to transition from a solid to a liquid state. As a result, the temperature remains steady until all the ice has melted.
Liquid Water (Increasing Temperature, Increasing Energy): Once all the ice has melted, the temperature starts to rise again as the energy supplied continues to increase the kinetic energy of the liquid water molecules. The temperature increase is gradual and follows the familiar linear relationship.
Boiling Point (Constant Temperature): As the temperature reaches the boiling point (100 degrees Celsius or 212 degrees Fahrenheit at standard pressure), it remains constant again. This period is known as the latent heat of vaporization region. The energy supplied is used to break the intermolecular bonds between water molecules, converting the liquid water into water vapor (steam). The temperature remains constant until all the liquid has vaporized.
Gaseous Steam (Increasing Temperature, Increasing Energy): Once all the liquid has vaporized into steam, the temperature starts to rise again as the energy supplied increases the kinetic energy of the steam molecules.
The heating curve demonstrates the energy changes and temperature plateaus associated with the phase transitions from ice to water (melting) and from water to steam (vaporization).