What is "dissolve?" That word has lots of meanings, but when we talk about liquids, and use the word "dissolve," it means "to become liquid." There are some substances that are solid or "hard" that will turn to liquid and mix in with liquid when they are put into a container of liquid.

We have here some sugar cubes, marbles, salt, nails, soil, coins, and powdered soap. We have 7 small jars that have water in them. We will put sugar cubes into one jar, marbles into another jar, and so on, until each solid thing we have is in a jar of water. Each jar needs to be stirred or shaken (sometimes shaking a jar of liquid is messy, so we'll put lids on the ones we shake), then let them stand a few minutes to see if the stuff in the water will dissolve or not. It would be a good idea to keep track of the time it takes each solid to dissolve.

It is fun to watch sugar cubes dissolve, isn't it? They sort of change shape, and get smaller and smaller, then they are gone. Where did they go? They dissolved. They turned into liquid, and if the liquid were stirred, the sugar would be mixed with the water.

Did the nails dissolve? It's a good thing they didn't, because if nails could dissolve in water, our houses would fall apart when it rained!

Let's make a list of things that dissolve in cool water, and another list of things that do not.

We can try it again with warm or hot water, and by keeping track of the time, we can list things according to how fast they dissolved. That way, it is easy to tell which
temperature of water is best for dissolving things.

Different liquids can be tried, and different kinds of solid things. If we try to dissolve solids in alcohol or gasoline, we must do it with adult supervision, outside, and be very careful that the alcohol or gasoline do not get heated. Alcohol and gasoline burn, and can be VERY DANGEROUS.