We put a small bit of water in an aluminium can. As it boiled it turned the water into a gas state which pushed out the air in the can. When the can was turned upside down in the cold water the gas quickly cooled and condensed back to a liquid pulling in the metal as it did so. A cool experiment! We write a procedure for doing this experiment and then an explanation of what was happening to cause the can to implode. We also watched a video of the same concept on a bigger scale.
We also looked again at how when atoms are heated they 'shake' more violently. We were able to see this in action when we dropped some food colouring into both cold water and hot water. The food colouring spread more quickly through the hot water as the atoms were more active.
Because atoms shake more when heated they need more space to move so they spread out. The more they are heated the more they spread out. They spread out so much that solids can no longer remain as a solid so they turn to a liquid. If you keep heating them they spread out more and the liquid becomes a gas. If you keep heating them then you will get plasma. When you boil water the bubbles that rise are actually the H20 turning into a gas as it is heated. They start at the bottom of the jug because that is closest to the heat.
So we have seen that heat affects density, but we also looked today at how different things have different densities just because of the way they are structured. We looked at how salt water is more dense than fresh water. This gave us lots to think about in terms of things like boats, swimming, survival in deep water, and free diving. Could you dive deeper in fresh water as it is less dense that salt water?
I showed them this photo of me in the dead sea in Israel to help explain differences in water density because of salt content.
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