When I was a kid, my grandparents kept years worth of yogurt containers. We made room-sized pyramids, and castles, and all sorts of stuff. It was one of the coolest things around.

At some point around 5th grade, I went to get a pot of leftover soup from the fridge and couldn’t get the lid off. My dad happened to be home, and explained how when gas (such as steam or air) is heated, it expands, and when cooled, the same volume contracts, reducing the pressure. The outside pressure then “pushes” on the lid, making it hard to open until you break the seal keeping that lower pressure inside the pot intact. Talk about a practical example of ideal gas law.

In fourth grade, my mom helped me make red cabbage juice to bring in for show and tell. It’s a natural litmus test – changes color depending on the ph of the liquid it’s added to.

I made a volcano this week with my 3-year-old as part of our letter of the week – V. Tiny glass vase, 9×9″ glass baking dish to catch it all, play dough to form the volcano, baking soda and vinegar plus a couple of drops of food coloring for the eruption, and his “what did you bring for the letter V” was a huge hit in his little one-day-a-week preschool class.

Kids will play with and learn from almost anything. Expensive toys aren’t really necessary, but an adult open to the curiosity and experimentation that comes with kid play can really enhance the experience.