This spring and summer we have looked at states of matter. We looked at solids here, liquids here and here and gases here and previously also here. This is only a part of the story so to speak. We have also conducted several experiments on the transformation between one state of matter and another. We looked at how boiling water transforms the liquid water into gas (water vapour). Warming the water adds energy to the water molecules allowing some of them to break free and become gas. This transformation is called vaporisation.
This past winter daughter also decided an experiment of her own on the conversion of solid to liquid and back. This was her very first own experiment that she decided on, planned and executed. I just took pictures. The substance she chose was snow, that was abundant at that time. She brought some in the house in a metal cup and wanted to melt it in front of our wood burning oven. We watched (intermittently) as it melted into slush and then into liquid. Now solids become liquids if sufficient heat or pressure is applied. We used heat in the form of a wood burning oven and the transformation is called melting. Then we took it outside to freeze again. The air temperature was somewhere around -14C, so it froze fairly quickly. What happened was that the energy we added into the matter to change it from solid to liquid (heat) followed the laws of thermodynamics. Heat always transfers from hot to cold, so the heat that allowed the water to remain liquid moved to the colder air removing the energy turning the liquid water back to solid ice. We got some beautifully pink ice due to some of her other experiments with the same cup. This is a very easy experiment done anywhere where there is snow in winter. And if you don’t have an oven, then it will melt in room temperature. It will just take longer. If you live somewhere where there is no snow, then using the freezer will work. In that case the starting point will just be water. Pop some in a cup and put into the freezer and wait. When it is frozen, bring it back to room temperature and let it melt.
We did the similar experiment with water and milk. We put a small amount of both in plastic bottles and put them in the freezer and let freeze. The milk froze first. It was frozen solid before the water even started to freeze. There was less of it, but also milk has some solids in it, so that helps too. Then we brought them inside and let melt. In the image below on the right it is also possible to note that the air inside the bottle is more dense now that it is cold than when it is at room temperature causing the sides of the bottles to cave in a bit.
We also did an experiment with chocolate, much to the dismay of my daughter who just wanted to eat it. We made a compromise. I cut out just a little bit of the chocolate and we melted it just a bit. We melted it by putting a larger cup in the bottom and filling it with boiling water. Then we put a glass in the boiling water and the chocolate in it. The (then nearly) boiling water started to melt the chocolate quite quickly. After a bit was melted daughter ate the rest. But we saw that heat turns a solid chocolate into liquid. This was a familiar concept as I have often told her not to hold chocolate in her hand as the temperature of her hand will melt it.
If you try these experiments at home and your child asks questions, please let me know what types of questions they ask in the comment section so I can further develop these instructions. If you have questions about these experiments or instructions, leave me a comment and I will answer and also improve these instructions. Also, please remember like and share if you find this useful.
Updated 9pm 18th of July: Added the missing links in the beginning
Copyright text and images: Satu Korhonen. You are free to try these experiments out, use them in your teaching. But instead of copying the text or images, link back to this page.