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Salt Water Density Experiment

This super easy science experiment will help children understand the term “density” and why it’s so easy to float in the ocean compared to the river or lake!

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Will it sink or float?

Children are never too young to learn big words! This fun experiment allows children to explore the concept of ‘density’ and how different solutions affect objects differently. Grab a few clear glasses, grapes, salt, sugar and sparkling water to see how the different liquids affect the grapes! Continue the conversation with how easy it is to float in the ocean versus a pool or a lake.

📚 Books to explore: What Floats, What Sinks by Jennifer Boothroyd is a great book for young kiddos to begin to understand density and more scientific terms!

🌊 Did you know? The Dead Sea is one of the saltiest bodies of water on Earth, with almost 10 times more salt than ordinary seawater!

💦 Keep the learning going!  What other liquids can you experiment with? Vinegar, rainwater, milk, juice, honey water...the possibilities are endless! Do these different liquids have different effects on the grapes?


For this activity you will need:



4 clear glasses

½ cup table salt

½ cup sugar

Sparkling water

Sticky notes or tape


Learning Outcomes




Measuring length, weight, capacity, temperature, time and money


Using conventional units of measurement


Step 1:

Pour the sugar into one glass. Fill almost to the top with water and stir.

Step 2:

Pour the salt into one glass. Fill almost to the top with water and stir.

Step 3:

Fill one glass with sparkling water.

Step 4:

Fill the remaining glass with plain water as your “controlled variable” liquid.

Step 5:

Label each glass with sticky notes or tape.

Step 6:

Place a grape in each glass to see what happens! How does each glass compare to the “controlled variable”?

⬆️ For older preschoolers:  Introduce scientific terms like “controlled variable”, “mass”, “volume” etc. Encourage them to use these in other experiments!

⬇️ For younger toddlers: Younger kiddos may not be interested in the “why” behind the reason for the floating “fish” that’s ok! Having them visually see the difference between the liquids can be just as exciting visually!

Playful Questions

Does the salt in the ocean help the fish float?

Have you ever floated in an ocean or pool? Was it easy?

If we add more grapes to each glass will they also float/sink?

What will happen if we add more sugar or more salt to their respective glasses?

What happens if we mix all the substances together? Will the grapes float or sink?

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