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You’re In Hot Water

In this simple demonstration, students make predictions and then observe the transitions between liquid and gas states of matter.

Using water is a simple way to show the three states of matter, and also the easiest to show the transitions between each state.

At room temperature, water is in its liquid state. It can easily be converted to gas state by heating it up as its boiling point is only 100 degrees Celsius. It can also be frozen readily because its freezing point is below or at 0 degrees Celsius to illustrate the solid phase. 


  • Describe the properties of a solid, a liquid, and a gas.

  • Describe the transitions between different states of matter.


  • Per Demo or Class:
    beaker, or a heat resistant container to boil water in
    hot plate
    lid or cover for container
    gloves for holding the container with boiling water if there is no handle

Key Questions

  • What is the name for the change of states occurring in this demonstration?
  • Why do water droplets form when a lid is placed over boiling water?

What To Do

  1. Ensure the students are a safe distance away from the hotplate, and remind them not to touch the hotplate.
  2. Start boiling the water on the hotplate.
  3. While the water is being heated up, ask the students for their predictions on what you are trying to show them as a way of gauging their prior knowledge and understanding of matter.
  4. Once the water is boiling and bubbles are visible, ask the students what they notice. What is happening to the liquid water?
  5. Discuss their ideas and then bring up the idea students that the liquid water is becoming gas. You can prove it to them by holding the cover over the boiling water and then showing the children the water droplets that form. Explain to them that the water is becoming gas and then becoming liquid again when it loses some heat energy by being in contact with the cover’s surface. This is a great way to show that temperature plays a role in the change of states.
  6. Turn the heat off the hotplate once the water is boiling steadily.