Here is a sealed tub of ice. Soon it will be a puddle of water inside the tub. Will it then weigh more, less, or exactly the same?
Hands up your guess.
Today's words: state means solid, liquid or gas. Mass is how much material there is, read on the balance, and a bigger mass reads heavier. Particles are the tiny pieces the material is made of.
When ice melts, does the amount of material change, or just its shape?
Each group has a sealed tub of ice and a set of scales. If the class shares one balance, we weigh each tub at the front bench together.
Before you weigh, say your prediction out loud to your group: after melting, will the tub read more, less or exactly the same?
- Weigh your sealed tub now.
- Write the reading on your Investigation Journal page.
- Leave the tub somewhere warm to melt while we work.
- At the end, weigh it again and write that reading too.
Watch the sealed clear bag with a little warm water trapped inside. The warm water turns into an invisible gas (water vapour). On the cold side of the bag it turns back into tiny droplets you can see. It is the same water, still trapped in the bag.
We cannot see the tiny particles, so let's look at them on the screen. Warm the material up and cool it down, and watch what the particles do in a solid, a liquid and a gas.
Notice: the particles never change or disappear. Only the way they move changes.
What are the particles doing?
On your Investigation Journal page, write the mass before and the mass after (copy them from the front bench if the class shared one balance), and one sentence about what actually changed when the ice melted.
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