It seems like magic to drop something in a jar of water, stir it around, and watch it disappear. Dissolving involves putting a solid into a liquid, causing it to pass into solution. During this process, the solid spreads out in between the water molecules, and the solid 'disappears.' Discover which solids dissolve in water and which ones stay solid.
Materials: Solids to dissolve - sugar, salt, rice, flour, candy, etc. Clear glass jars, some bowls with water (you can use hot and cold water if you want to compare the differences in the speed of dissolving), an empty bowl to dump dirty water into.
Set out your materials. You may want to set your supplies outside, or on a tray. Ask your children 'what dissolves in water.' You can either let them go for it, or help them test one item at a time, dumping out the dirty water each time. For older children, you can create a list of results, either way, this discovery is a great time to talk about making hypothesis. Even little ones get the idea of 'guessing' what's going to happen.
We started our discovery by melting ice in hot and cold water (this is technically melting, not dissolving) to show the idea that things disappear faster in hot water than cold water. After that, the kids became very methodical (for 4 year olds) about dissolving each solid and dumping the dirty water and getting fresh water. We did notice that the hot water dissolved things faster. A few of the items, such as the candy, we decided to leave overnight to see if they would completely dissolve.
We finished our discovery by putting baking soda with vinegar, just because it's fun.
I shared at: Taming the Goblin