See what we did for other letters in the Alphabet in Simple Science.
D for Dissolve
Kool-Aid Packet, Water, and clear cups
This investigation was pretty simple. I set out three cups of water. Then we dissolved a little bit of Kool-Aid to one cup and the rest of the packet to the other. After making observations about differences in color, smell, and taste, I had him predict what would happen to the cup with most of the Kool-Aid in it if I added a lot more water. I then poured all the cups in a pitcher and added the remaining water left on the recipe (2 Qt, I think). We talked about the color changes. I poured off just a little bit into a cup, then I had him pour in the sugar. At first, all the sugar sat at the bottom. I asked if that sugar had dissolved yet. Then we stirred it all up and I asked him where the sugar went. Then I let him compare the Kool-Aid with sugar and without sugar.
For the most part, I just asked Xander what he noticed after I mixed the little bit of Kool-Aid in. I asked him where the powder went and if we could still see any of the powder. With the third cup, we discussed the changes in color and that some of the powder was still left because it had not all dissolved. After he tasted all three, I asked which he liked better and why. He said the dark one tasted pretty sour! When we made the big pitcher, I asked him where he thought the sugar went. We talked about how the sugar changed the liquid. I asked him which one he liked better and why he liked it better. Basically, through the whole conversation, I emphasized the idea that the powders dissolve into the water, but they do not disappear.
With older kids you could definitely talk about saturation point. You could also bring in temperature and investigate whether things dissolve better into hot liquids or cold liquids. If I had had time, I would have also liked to dissolve some salt in water, then boil the water off to prove that the salt didn't disappear.
Marshmallows, clear cups, various liquids
We put Sprite, orange juice, apple juice, lemon juice, hot water, and cold water in clear cups. Then we put two marshmallows in each and stirred. I asked Xander to tell me what he thought would happen to the marshmallows. We walked away for a while and came back to check on them. We found out that only the hot water dissolved the marshmallows. Then he ate ALL of the remaining marshmallows (including those in the lemon juice).
Before we added the marshmallows, I asked him what he thought would happen. Then as we were stirring, I asked him what he noticed and if he saw any of the marshmallows starting to dissolve. After we came back, I asked him to look in each one and see if any dissolved. When he found the one that did, I asked him what happened to the marshmallows. Did they disappear? Did they go away by magic? And we discussed that dissolving meant you sometimes couldn't see it anymore, but that it was still in there.