Sink or Float - Easy Science for Kids

You might think sink or float experiments are just for small children, but you can do some great investigations with older children along the same theme.

Do you know how to make a lemon sink? Or can you make an object that sinks, float?

make a lemon float. Image shows a container filled with water. A whole lemon is floating at the top and the inside of a lemon is at the bottom.

Sink or float investigation for little ones

You’ll need

A large bowl of water

Objects to test (anything you like, but good to pick some solid and some hollow objects)

Instructions

Fill the bowl or container about ⅔ full of water.

Gently place the objects on the water; some objects will float when you gently put them on the water but sink when you drop them.

Can you predict which objects will float and which will sink?

Can you design a table for recording your results?

Another idea is to set up a pirate style sink or float experiment or a lego themed investigation is great fun too!

Young child dropping items into a transparent box of water

Why do some things float and some things sink?

Whether an object floats or sinks depends on its density. Density is how tightly packed the material inside an object is. Just because something is heavy does not mean it will sink. For example, ships are very heavy but not very dense, so they float.

Child's hands in water. Different objects are floating in the the water.

Something else to try is to make a boat from plasticine and use it to demonstrate how marbles or something similar sink on their own but hopefully float inside the boat.

More sink or float science experiments for kids

Make boats with recycled materials and test them to see if they sink or float. Try adding extra weight to investigate how much they can hold without sinking!

Make an egg float using salt. Adding salt to water increases the density of the water. If the water becomes denser than the egg, the egg will float!