The next concept was a tough one. To teach my daughter that solids can turn into liquids if you add heat. This was an overview of our conversation:
Myself: "What season just finished, when it was really cold?"
Myself: "What was on the ground in the winter?"
Daughter: "Snow. Lots of snow."
M: "What happened to the snow?"
D: "It melted."
M: "How did it melt?"
D: "Cause the sun came out and melted it. It got hot."
M: "Ah, so the heat from the sun melted the snow? What did it turn it into?"
D: "Water. There were lots of puddles."
After this conversation, I told her that when things got hot, they changed from a solid to a liquid. Together we started on our project. My daughter ripped the paper off of the crayons that I gave her (*NOTE* The cheaper crayons are harder to peel - it also helps to did the crayon in water) and while she did that, I cut the crayons into small pieces (not shaved).
M: "So how do we turn these crayons into a liquid?"
D: "They have to get hot. The microwave?"
M: "That wouldn't be hot enough. Something bigger maybe?"
D: "The oven! Let's put them in the oven!"
We put the small pieces into a muffin tin and put them in the oven (230F) for 15 minutes. In the end, this was a really cool learning activity and we had so much fun together! She coloured with her crayons for days and even took them to school to show her teachers and friends!
There are many different activities that you can use to teach your child the difference between solid and liquid. I think my favourite is a simple recipe for Goop. It is a solid, but turns to a liquid when you touch it. The recipe is simply:
Food coloring (optional)
Add the food colouring to the water, then add one part cornstarch to one part coloured water.
Getting more into the science behind the change, simple ice cubes are probably the best way to teach heat and change.