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Heating and cooling curves

# Heating and cooling curves

## Explainer Video

Tutor: Aimee LeBrun

# 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

### Which two state changes are looked at in a cooling curve?

Beta

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