Simple Science Project For Kids: Float or Sink

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I love float or sink experiments. They have so much learning potential, are easy to set up, and offer different variations to sneak in STEM skills. The overall aim of this simple science project is to find out if objects float or sink. Kids love this because it is simple enough that they can do it independently and even draw conclusions by themselves. This helps them build confidence in their abilities as curious little explorers. 

simple science project float or sink

I can’t remember exactly when we started doing float or sink experiments with our oldest but I know we have done it a lot, in many different ways. At first we used her toys in the bathtub to see if they would swim or dive and eventually the proper vocabulary found its way. Developing scientific vocabulary in kids is such a great way to engage them in STEM. If they build this vocabulary around fun and hands-on experiences you are making it easier for them to better understand the concepts. Rather than explaining what float or sink actually means they are observing and testing for themselves and this simple science project is just perfect for that!

Simple Science Project For Kids: Float or Sink

There are many ways to do this project so first I will share different variations you can pick and choose from. Then I will give you an example of how we made our own simple science project and incorporated STEM learning with float or sink experiments. However you do it, remember that if you are combining young kids and water things are bound to get wet! Try to plan to do it outside or prepare a space that can get a bit wet so you are not worrying about this all the time. So here we go…

There are basically two ways to test if something floats or sinks:

  • Drop it in a bowl full of water
  • Place it in an empty bowl and fill the bowl with water

Questions you can ask to get your kids’ minds working:

  • What happens to an object when it floats/sinks?
  • Does it stay on the bottom?
  • Or does it stay at the top?
  • How can we find out if something floats or sinks?
  • For older kids: with your eyes closed, how would you find an object that floats/sinks?

Different ways of observing and working on STEM skills:

You can do a number of different things when you are engaging with your kids in this simple science project. From letting them discover and experiment by themselves, to guiding the activity a little. I always love to try a bit of both and observe my kid to see if she is up to being guided. Most of the time she will follow my lead but many times she just wants to do her own stuff, and that is totally fine too! So here is some inspiration if you are looking to guide the activity:

float or sink

Sorting and categorizing

This is a great STEM skill to practice. The obvious categories are float and sink but feel free to come up with more! Have two containers with the words float and sink and have them sort and categorize them either by testing first or by guessing and then adding water to see if they were right.

Testing, observing, and drawing conclusions

Have your kids test the different objects, observe and comment on what is happening. We discovered that green pine cones sink but brown ones float so it is not possible to say that pine cones in general float, which was my first thought! I love learning new things with my kid and showing her that I don’t know everything. I hope to foster a love for learning and a tolerance for making mistakes and not having all the answers right away.

Making hypotheses

Gather all the materials and have your kids make a hypothesis, a statement that needs to be proven. Set up an experiment to test the hypothesis and see what happens. 


We can use this simple science project to sneak in some counting practice. Find out how many objects float and how many sink, which category has more items? Use 10 objects and work on ten frames. Keep a tally board while you are testing. Give each kid a clipboard and paper and have them keep count (tally) as they test, this is true scientific research!

Develop scientific vocabulary

When doing projects like this one always remember to talk to your kids about what is happening. Use the scientific words and help them build their vocabulary through hands-on science projects like this one. Explore what it means to float or sink, use other catergories such as size, weight, shape, color or texture. Basically it is important that you talk with your kids about what you are observing.

science float or sink

I hope these ideas give you some inspiration to explore with your kids and create your own simple science project for testing whether things float or sink. If you still want some more guidance and want to know how we did it keep reading. My kid and I were entertained for over an hour! Feel free to do it like we did or find new ways that better adapt to you and your family.

Our Float Or Sink Simple Science Project


  • Natural materials
  • 2 bowls for sorting/categorizing
  • 1 large transparent container for testing/observing 
  • Paper and pens
  • Water
natural materials

Simple Science Project Steps

Here are the steps that we followed to experiment with natural materials and the concepts of float or sink:

1. Gather natural materials

This is one of my favorite pre-project activities! Go on a nature walk and collect some materials, be sure to collect a bunch of different things and explore as a family. 

2. Create a sorting station

Lay out your natural materials, take out the 2 bowls of sorting and label them. I used 2 different bowls and different colored paper for the label to make it easier to sort and categorize. Prepare a testing container full of water and let your kids go ahead and test the materials and then put them in the right category. Observe and talk about what is happening. Use scientific vocabulary.

3. A bit of play in between

It’s good to not go from one activity to the next but rather to let our kids explore a bit by themselves and go off topic a little bit. Sit back and just watch your kid play a bit, comment and observe with them.  

4. Involve the senses

Add different materials into the testing container and have your kid find different objects while they keep their eyes closed. See if your kid can find something that floats/sinks and use this time to ask some questions:

  • Where can you find different materials if they float or sink? 
  • Top or bottom of the container? 

5. Finish off by testing in a different way

Ask your kids to sort the objects again without testing them first. They should try to remember what floats and what sinks. Once the natural materials are sorted into both bowls ask them what they think will happen with the materials that sink/float? Then fill the bowls with water and find out if they got them right! 

simple science project

As I said before, feel free to do this float or sink experiment following these steps or create your own project using this information as inspiration. It is so simple and yet so entertaining for young kids and toddlers that I’m sure that once you discover it you will be doing it more than once!  

Summary of STEM Concepts and Skills for the Float or Sink Simple Science Project:

  • Sorting and categorizing 
  • Making hypotheses 
  • Testing
  • Observation 
  • Math/counting 
  • Developing scientific vocabulary 
    • Float/sink
    • Weight: Heavy/light
    • Size: Big/medium/small

If you’ve made it this far, congratulations! I know that was a long post for such a simple science project. But that is the beauty of this project, it has so much STEM learning potential! Hope to have inspired some float or sink moments at home with your kids. Check out this other lovely float or sink experiment if you want to go into the topic of density.

More Fun Activities and Games:

float or sink

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