Heating and cooling curves
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Explainer Video
Summary
Heating and cooling curves
In a nutshell
Heating and cooling curves can be used to explain how energy changes during a change in state.
Heating and cooling curves
Definition
Heating and cooling curves show energy changes during a change in state. These diagrams show how temperature change stops for a period of time when a material changes state.
A flat line on a heating or cooling curve indicates the temperature doesn't change.
Heating curve
The graph shows the relationship between time and temperature when a substance is heated.
1. | When a substance is heated the temperature will rise. |
2. | During melting or boiling, energy is being used to weaken forces between particles rather than raise the temperature. The temperature is constant, this is represented by a flat line on the heating curve. |
3. | The flat line at the lower temperature represents the melting point of the solid and at the higher temperature represents the boiling point of the liquid. |
Cooling curve
Below is a graph showing the relationship between time and temperature when a substance is cooled.
1. | When a substance is cooled the temperature will fall. |
2. | During condensing and freezing, energy is given out as the forces between particles gets stronger. |
3. | Temperature will not fall during condensing and freezing until all of the substance has changed state. |
4. | The flat line at the lower temperature represents the melting point of the solid and at the higher temperature represents the boiling point of the liquid. |
Example
The temperature of a substance is decreasing, what type of curve should be used when considering the energy changes during a state change?
A cooling curve, the temperature is falling so condensation and freezing should be considered.
FAQs - Frequently Asked Questions
What do heating and cooling curves show?
Heating and cooling curves show the energy changes happening during state changes.
Which two state changes are looked at in a heating curve?
Melting and boiling are the two state changes that occur in a heating curve.
Which two state changes are looked at in a cooling curve?
Condensation and freezing are the two state changes that occur in a cooling curve.