Sink or Float: A Preschool Science Experiment

Preschool science experiments are a joy. I’ve never met a child who doesn’t enjoy experiments…there’s something about moving things around and often getting a bit messy that awakens curiosity, excitement, and wonder.

Well, it’s been a few months since we did this, but Peanut really enjoyed a common preschool science experiment called “Sink or Float.” It’s about as simple as it sounds!

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Here’s what we did:

I gathered some materials that sink and float such as: a coin, a plastic medicine cup, a twig, two rocks, and a lemon. There ended up being 3 items that floated and 3 items that sank. I suggest you look for items that are made out of different materials such as wood, plastic, food items, metal and nature items. We’re lucky to live near a volcano, so one of the rocks was pumice, and so it floated!



I also prepared 2 labels, one which said “sinks” and one that said “floats.” You’ll also need a rag or cloth handy. We also used a magnifying glass for careful observations of each of the objects. Here’s the setup:

Preschool Experiment Setup

To present this to Peanut, I invited him to the carpet and had him fill up a large, glass bowl. Then, I demonstrated placing one of the items that sank in the bowl and noticing how it sank. I said, “It sinks”. Then I placed it under the label “sinks”. We noticed how it started with the “ssss” sound. Then, it was Peanut’s turn. He figured out very quickly which label was which and also enjoyed looking at each of the items with a magnifying glass. He LOVED how one of the rocks floated and the other sank…and observing the holes in the pumice.

Preschool Experiment with Magnifying Glass

A few days later, he had gathered a whole collection of rocks ready, saying “Mama, these are for my school.” I guess we’ll have some rock study coming up soon. Luckily we just got a National Geographic book about rocks from Grandma and Grandpa. What a lucky boy!

So, that’s how you can do a simple experiment with your preschooler.

Here’s Peanut in action:

Looking for an extension?




We repeated this experiment with salt water and fresh water while studying the ocean. The salt water meant that some things floated that would usually sink in fresh water. We had luck with a slice of carrot which floated in the salt water, but not in the fresh water. I think it really takes a lot of salt to make much of a difference. In any case, we enjoyed learning about fresh water and salt water.

Hope you enjoyed it!

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