In the following video, scientist, songwriter, and all-around Renaissance man, Mark Rosengarten explains how simple phase change diagrams are made and how to read them.
Study the heating curve above. A heating curve shows how the temperature of a substance changes as it is heated. Generally, a heating curve starts with the substance in the solid state and continues until the substance reaches the gaseous state. Notice that as heat is added to the solid, the temperature rises (A). As the solid begins to melt, the temperature becomes constant (B). During a phase change, all of the energy added to the substance is used to change the phase of the substance. This results in no temperature change. Once all of the substance has changed from the solid to the liquid state, the temperature begins to rise again (C). As the temperature of the liquid rises, the boiling point is approached. Once it is reached, the substance begins to change phases, this time from the liquid to the gaseous state. During this phase change, all of the energy added to the substance is used to change the phase of the substance. This results in no temperature change (D). After all of the liquid has turned to gas, the temperature of the gas begins to increase (E).
The following song by Mark Rosengarten describes the physical changes and the molecular characteristics of water as it undergoes phase changes from solid to liquid to gas, and what happens to temperature as the change progresses.
Self-Assessment and Practice
Match each term to the correct letter from the diagram above.
2. liquid and gas
3. solid and liquid
Click here for the answers.
1.C, 2.D, 3.B, 4.A, 5.E