Solids, Liquids & Gases

Activities to try

1. 1

   Test the state bench: pour, seal, observe, sort

   Why it works: A material's state is decided by how the material itself behaves (does it keep its own shape, take a container's shape, or fill all the space), not by whether it pours or how it looks. Sand pours but is a solid because each grain keeps its shape.

   1. Take each mystery substance and pour or place it into jars of different shapes; observe and record what happens.
   2. Note which items keep the same shape in every jar (e.g. a wooden block) and which pool flat and take each jar's shape (e.g. water); then observe a gas swelling to fill a whole sealed jar (shown via a simulation/animation or a pre-prepared safe sealed demonstration — not a real coloured gas released in class), and see in the simulation that an open container would let the gas escape.
   3. For the water, pour the same amount into several differently-shaped containers; confirm the shape changes while the amount stays the same.
   4. Drop each tested item into a solid / liquid / gas bin and attach a short behaviour tag stating WHY (e.g. 'keeps its own shape', 'takes the jar's shape and lies flat', 'fills the whole space').
   5. Test sand deliberately: pour it (it pours a bit like a liquid, but it heaps into a sloping pile instead of lying flat like water), then look closely at a single grain — note that each grain is hard and keeps its own shape, so classify sand as a solid because the GRAINS keep shape even though the pile pours.
2. 2

   Steam vs the white cloud

   Why it works: True water vapour (steam) is an invisible gas; the visible white cloud above a kettle is tiny condensed liquid droplets, not the gas itself. 'I can see it, so that's the gas' is the belief to correct.

   1. With an adult handling the kettle safely, watch a boiling kettle and look for the small CLEAR gap right at the spout before the white cloud begins.
   2. Before any reveal, predict which part is the actual gas (the real steam) and explain why.
   3. Watch an adult hold a cold plate or spoon in the plume: observe droplets of liquid water forming on it.
   4. State in your own words: the invisible part near the spout is the gas (water vapour); the white cloud higher up is tiny liquid droplets that have cooled and condensed.
3. 3

   Gas is real stuff

   Why it works: Gases are real matter: they take up space and have mass, even though they are usually invisible. An 'empty' sealed bottle is actually full of air.

   1. Trap air by sealing a bag or squeezing a capped bottle; feel the resistance and note the gas takes up space.
   2. Blow bubbles or feel a puff of air on your hand to sense that the invisible gas is really there.
   3. Compare a ball pumped up hard (e.g. a football inflated with a pump) with the same ball when soft. If a sensitive balance is available, weigh it both ways: the hard-pumped ball should weigh slightly more because extra air has been squeezed in. Discuss whether the gas has mass. (A balloon blown up by mouth is not a good test: the air inside is barely squeezed, so a classroom balance will show little or no difference.)
   4. Answer: can you see the air in this room? Is it still a gas even though it's invisible?