Fun Sink or Float Science Activity for Kids

This Sink or Float science activity is fun for little kids. There is scientific explanation as to why things float or sink. But for the kids it is first important to get familiarised and experience the sinking and floating of different objects of different shapes & sizes. Yes a pine needle will float, a wood log will float but a coin will sink, a grape will sink, why?

Well whether an object sinks or floats depends on its density and buoyancy.

Density is all about molecules. Every object is made of molecules, some have tightly packed molecules. Others have molecules that are packed more loosely. Objects with tightly packed molecules are denser and hence sink. Objects with more loosely packed molecules are less dense and float e.g. plastic.

Now for buoyancy, have you ever wondered how a huge ship made of metal floats and does not sink? Years ago, Archimedes, a Greek Mathematician was taking a bath. When he got into water, a certain amount of water got displaced and overflowed over the rim of the tub. Eureka! He came up with The Archimedes principle, that explains buoyancy. According to it, if the weight of the object being placed in the water is less that the weight of the water displaced, the object will float. This is known as buoyancy.

Now for the fun part of the activity.

Age: 3+

You will need:
A large container full of clear water
Objects that your kids would like to experiment with. My kids chose a magnet, coin, metal tortoise, metal spoon, a cherry, grape, plastic toy, a plastic bowl, metal bowl, a pine cone, a flower, a leaf.

Step 1: Place a container full of water on a table.

Step 2: Put all the objects you want to experiment with next to it.

Step 3: Ask the kids to guess which object will float and which will sink. You can even maintain a score to see who guessed better at the end.

Step 4: Now go for it, object by object and hear the kids shout with excitement. “Float!” “Sink!”
Note: Here are the objects from our list that floated:

sonu image
Here are the objects that sank:

Benefits: It is so wonderful for kids to understand floating and sinking as a concept. Next time they hit a swimming pool, teach them to float and they will make the connection.

Hope you enjoyed today’s summer science activity. Check here for more fun summer activities.

Comments (1)

Heidi Hisrich Posted on Jul 02, 2015

I love density experiments! Have you tried the Bubbling Bottle (lava lamp) or density layers? You can check out for some fun experiments you may not have tried out yet. Sounds like we have some similar interests:)


Charu Chhitwal

Charu Chhitwal, Founder KetchupMoms has daring tastebuds, a love for travel and an owl for her soul. It’s little wonder then that she loves to write and share her tips and tricks on traveling, food,

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