Salt Water Density Experiment

Do grapes sink or float?

Grapes can do both.

Whether a grape sinks or floats depends on its density relative to the water it’s in.

An object’s buoyancy is determined by its density compared with the density of the surrounding water.

Density of water can be changed by adding salt.

Let’s try this experiment to learn about the property of salt water density.

two grapes sink in one glass of water, another two grapes float in a glass of water

Do Grapes Sink Or Float? | Salt Water Density Experiment

Prep Time: 20 minutes
Additional Time: 30 minutes
Total Time: 50 minutes

This science experiment demonstrate the property of salt water density.


  • some grapes
  • 2 clear glasses
  • tap water
  • salt
  • stirrer


  • adult supervision


  1. Fill the two glasses with tap water.
  2. Put a few grapes into one of the glasses. The grapes should sink.
  3. In the other glass, add generous amount of salt and stir.
  4. Keep adding salt until no more salt can dissolve. The solution is now saturated.
  5. Put the remaining grapes into the saturated salt solution. The grapes in this glass should float.

Did you try this project?

Follow us on Pinterest and share a photo!

2 clear glasses of water, one with 2 floating grapes, the other 2 sinking grapes.


Have you ever wondered why some objects sink in water while others float? It has to do with the density of the object.

Density of an object is the amount of substance (mass) within the volume occupied by the object. If two objects occupy the same volume (i.e. same size), the one with more substance is denser than the one with less substance.

An object’s buoyancy is determined by its density compared with the density of the surrounding water.

If an object is denser than the water, it sinks. On the other hand, if an object is less dense than the water surrounding it, it floats.

Grapes are denser than freshwater. That’s why they sink to the bottom when you put them in a glass of tap water.

Adding salt to the water increases the mass of the water without changing the volume too much. So the water becomes denser.  When you add enough salt, the water can become denser than the grapes. Therefore, grapes can float in the saturated salt water.

What floats in salt water?

Grapes are not the only objects that can flow in salt water. Many objects can float easily in the ocean because it contains salt water. The Dead Sea is famous for its extremely high density salt water and people can easily float in it without much effort.

Woman reads a book while floating In the Waters of Dead Sea is a salt water density experiment preschool

Similar Posts