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20 October 2014
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Gases, liquids and solids - lesson plan

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A can in a glass beaker

  1. To understand that gases are formed when liquids evaporate and that when a gas is cooled it condenses to form a liquid.
  2. To understand that gases move and flow more easily than liquids and in all directions.
  3. To understand that gases differ from solids and liquids in that they do not maintain their shape and volume but spread out to fill the space they are in.

National Curriculum

Sc3, 1e, 2b, 2d.


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Teaching activities


  1. Watch Learning Zone Class Clips - The behaviour of particles.
  2. Ask the children, as a class, to act as a solid, then a liquid, then a gas, reinforcing the movement and amount of energy the particles have.
  3. Display the word labels.
  4. Ask the children what happens when you heat a liquid. Demonstrate by boiling water in the kettle.
  5. Ask the children to explain what they see, using the displayed words. Where does the gas go?
  6. Boil the kettle again but this time near a cold window.
  7. Ask the children to feel the window (it is cold).
  8. Ask the children to watch the window to see what happens when the steam touches it and cools down (it condenses and becomes a liquid again).
  9. Watch the clip Learning Zone Class Clips - Particle Theory - liquid into gas.
  10. Ask the children to draw a picture representing the changes from a liquid to a gas (through heating) and from a gas to a liquid (condensing).


  1. Write these questions on the board: What shape does a gas have? How does it move?
  2. Explain to the children that as gases are often invisible, these questions are difficult to answer.
  3. Using the Bitesize gases, liquids and solids activity ask the children to sort the materials into solids, liquids or gases.
  4. Explain to children how to use the Heat and Cool controls. Arrange the children in pairs or groups, with a computer for each group. Ask them to work through the online activity, following the tasks that are written (and spoken) at the top of the screen.


  1. Give the groups key questions on the activity to answer in pairs: What happened when the liquid was heated? Where did the gas go? What happened when the lids were removed from the beakers? Where did the gas go then?
  2. Elicit the ideas that gases spread out when they move and do not keep their volume and that they take the shape of the whole container be it the room or the two beakers.
  3. Ask the children why, when the lid was on the beakers, did the liquid form in both beakers when it was cooled?
  4. Ask the children to draw particle pictures and label them with key facts about each state of matter.


Ask the children to complete the Bitesize gases, liquids and solids quiz.


Give the children a picture of a kettle of water boiling. Can they explain scientifically what happens to the water?

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