In this module, you will learn:

  • The changes of states of water
  • melting, freezing, boiling, condensation and evaporation.

Resources to help you:

  • Textbook: page 73, 74, 75, 76 and 77
  • Notebook: page 30 and 31

Watch the video

See how matter changes its states.

Source: https://www.youtube.com/watch?v=CMUmQRgJAo0

You can change the speed to 0.75x to make it easier to listen.

We see water in all 3 states in our everyday life.

Credit:@Wandeaw via Twenty20

The changes of states of water

Water like all matter can exists in all 3 states of matter; solid, liquid and gas. In this module, we will look at how water changes between these states.


The changes of states we will be looking at are:

  • Melting
  • Freezing
  • Evaporation or Boiling
  • Condensation

Melting

Melting is a process where solid water, ice, is changed into liquid water.


Ice has a melting point of 0° C.

This means if the temperature around the ice is higher than 0° C, the ice will start to melt.

Water Melting in a glass

Credit: @tolstnev via Envato Elements

Water freezing in a glass

Credit: @CameraMotor via Envato Elements

Freezing

Freezing is the process where liquid water is changed into solid water, ice.


Water has a freezing point of 0° C.

This means if the temperature around water is lower than 0° C, it will start to become a solid and freeze into ice.

Evaporation and Boiling

Both evaporation and boiling involves the process of the changes of liquid water into gaseous water, steam or water vapour.

However, there are some differences between them.

Gaseous water in the form of steam from a hot cup of coffee

Credit: @Taden via Envato elements

The differences between evaporation and boiling

Evaporation

Source: https://www.youtube.com/watch?v=-hu3Qn4828k


  1. Evaporation happens on the surface of the liquid.
  2. Evaporation occurs at all temperature below the boiling point of water (100° C).
  3. The temperature of the process of evaporation is not constant.
  4. Evaporation is a slow process.
  5. No bubbles are formed in evaporation.

Boiling

Credit: @Christian_Fletcher via Envato elements


  1. Boiling happens throughout the whole liquid.
  2. Boiling occurs at the boiling point of water only (100° C).
  3. The temperature of the boiling process stays constant.
  4. Boiling is a fast process.
  5. Bubbles are formed in boiling.

A bottle of cold water with condensation droplets of water outside.

Credit: @gcpics via Envato elements

Condensation

Condensation is a process where gaseous water in the form of steam or water vapour is changed into liquid water.


Condensation is also important in the formation of clouds.

Source: https://www.youtube.com/watch?v=dnL5LPil77M

Ready for the next module?

In the next module, we will look at solute, solvent and solution.

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