There are lots of great hands-on ways to explore chemistry with kids. (I cover them in these posts: States of Matter, Mixtures, Reactions.) Some of our favorites are Slime, Milk Fireworks and Oil and Water.)

Slime

Slime is all the rage of “mad science” parties everywhere, so it’s likely your child will make it many times throughout their childhood. There are TONS of recipes and variations if you search online. Here’s one that works for us:

1. Pour ¼ cup of glue into a plastic cup.
2. Pour ¼ cup of water into glue. Add 4 drops food coloring. Mix well.
3. Sprinkle in ¼ teaspoon of baking soda. (Optional: glitter.) Mix well.
4. Add 1½ teaspoons of saline solution. Stir FAST to combine.
5. When it starts to pull away from the sides of the cup, put just a few drops of saline solution on your hands and rub them together, then pick up the slime and knead it for a little while.
6. Once it’s solidified into a nice not-sticky slime, play with it.
7. When you’re done playing with it, put it in a Baggie to store for later.

Materials notes, with affiliate links: For the glue, we do 20 or 30 batches in one day for all our kids, so I buy a gallon of Elmer’s clear glue. You could also use their Color Changing Glue, Glitter Glue, or Metallic Glue or just their regular everyday school glue for a pastel slime. The contact lens saline solution MUST contain boric acid and sodium borate. Brands we’ve used: Renu Fresh, and Bausch + Lomb Sensitive Eyes.

What’s happening, kids’ version: Glue is made up of long strings of molecules that slip and slide past each other easily. When we mix in the saline  solution, chemicals in there tangle up those strings into this gooey mess.

What’s happening, for adults: The glue contains polyvinyl acetate, a strong and flexible polymer made up of long, repeating, identical strands of molecules. These strands slide past each other easily, making it easy to pour glue. The saline solution has sodium borate and boric acid. When it’s added to glue, the borate ions mix with the glue and connect the long strands together, cross-linking the protein molecules and borate ions so they can no longer easily slide past each other. They tangle and mix together

Some children LOVE slime and want to ply with it for hours. Some enjoy making it but then never touch it again. I don’t love the environmental impact of slime (it’s basically a big hunk of plastic goo) so we make small batches. I also hesitate to use glitter, since it’s little pieces of plastic. We generally avoid it in our class, but this is one project where I use just a little. I have not tried biodegradable glitter here, because it will degrade over a few weeks in this moist environment, I think.