We are on a role this Valentine’s Day with holiday themed science and STEM activities for kids. This week we have been working on quick and easy Valentine’s Day science activities you can do right in the kitchen. This water displacement experiment is the perfect example of how just a few simple supplies provide a cool learning experience for kids.


Valentines Water Displacement Science Experiment and STEM Activity


Get ready to add this simple water displacement experiment to your science lesson plans this season. If you want to learn what water displacement is and what it measures, let’s dig in!  While you’re at it, make sure to check out these other fun water experiments for kids.

Our science experiments and STEM activities are designed with you, the parent or teacher, in mind!  Easy to set up, quick to do, most activities will take only 15 to 30 minutes to complete and are heaps of fun!  Plus, our supplies lists usually contain only free or cheap materials you can source from home!

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I love simple science experiments and activities that go along with the upcoming holiday. Valentine’s day is one of the best holidays for themed science projects. We have tons of cool Valentines Day activities that are easy to try at home or in the classroom.

Valentines Day Chemistry

Science can be quick and fun with young kids. More and more I am realizing that you don’t need elaborate set ups to provide a great experience. As my son gets older we are venturing into science experiments over science activities.

CHECK OUT: Scientific Method For Kids

Often experiments and activities are used interchangeably, but there is a small difference. A science experiment usually tests a theory, has controlled elements, and some sort of measurable data.


When you put an object into water like our plastic love hearts below, it pushes water out of the way and takes the place of the water.  We say that water displacement has occurred.

Volume is a measure of the amount of space an object takes up. The cool thing is we can measure the volume of the objects we have placed in the water by measuring the water displacement.  If you measure the amount the water level increases in your container, you can find the volume of the water pushed out of the way.


We actually started this project as an activity. We had one cup with some water in it, not measured. I made a line with a marker, and we had a bowl of plastic hearts.

I had my son put the hearts into the water a few at a time. What did he notice? He discovered that the water rose above the line we marked. We made a new line. Pretty cool finding out that when we add an object to water it causes water to rise!

Valentines Day Water Displacement Science Experiment Activity Kids Holiday STEM


The purpose of the experiment is to see if the same amount of hearts and the same amount of liquid in different containers will rise the same amount. The parts that make this a good science experiment are the same amount of  water in each container and the same number of hearts for each container. What’s different? The shape of the containers!


  • 2 different size clear plastic containers {you can use more in varying sizes}
  • Package of red plastic hearts (for our Valentines theme)
  • 1 cup of water for each container
  • Plastic ruler
  • Sharpie

valentines Day water displacement set up and supplies used


STEP 1: Make sure to have your kids make a prediction of what will happen to the level of the water before starting the experiment.

STEP 2: Measure 1 cup of water into each container being used.

STEP 3: Mark a line on the container with a sharpie to show the current level of the water.

Use a ruler to measure and record the height of the water.

STEP 4: Place a bowl of plastic hearts (or other small objects) next to the containers. We only had one bag of these. So we did one container at a time and then dried off our hearts to start again.

STEP 5: Begin dropping hearts into the water. Try not to splash water out of the container as this will alter the results a bit.

Valentines Day Water Displacement Science with plastic hearts

STEP 6: Once all hearts have been added, mark a new line for the new level of water.

Use the ruler again to measure the change in levels from the starting mark to the ending mark. Record your measurements.

Valentines Water Displacement science tall bottle

STEP 7: Dry the hearts and start over again with the next container.

Valentines water displacement measuring difference in water level

Talk about what happened. Were the predictions correct? Why or why not? What was different or the same between the containers?

You can measure and compare the results of all the containers when your testing is complete. If you have an older child, you can set up a science experiment journal page to record your results and actually calculate the volume of water displacement.

Looking for easy science process information and free journal page? 

We have you covered…

—>>> FREE Science Process Pack

 Valentines Water Displacement science adding hearts to water

We tried not to splash! As we all know, it is fun to drop things in water and make them splash.

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Valentines Water Displacement Science Experiment



Click on the link or on the image below for our 14 Days of Valentine’s Day STEM Countdown!

Valentines Day STEM Activities