Download Density Demonstration: Floating Egg

Density Demonstration: Floating Egg
Saturday Science Club
Density Demonstration: Floating Egg
Author: Robby Ferguson
Activitiy Description
The following experiment demonstrates the property of density on the molecular level by using the
buoyancy of an egg to compare the properties of saltwater and freshwater.
Goals/Objectives
• To understand what the property of density is
• To learn the relative difference between the density of saltwater and the density of freshwater
• To understand what makes an object float or sink in some liquid
Needed Supplies
• 2 raw eggs
• 2 bowls/containers
• 6-10 tbsp of table salt
• tap water
Experiment Steps
1. Fill both containers with tap water from the sink.
2. Add the table salt to one container of water and stir the mixture until all of the salt appears to
dissolve into the water.
3. Ask the students if they have ever tried to swim both in a swimming pool and in the ocean. Does
it seem easier to float in a swimming pool or in the ocean? It should be easier to float in the ocean.
4. Explain that the density of the water (in either a swimming pool or in the ocean) is the property
that allows someone to float.
5. Define density to basically be how compact an object is (i.e., the density of an object is its mass
divided by the volume of space that it takes up). All objects have some density.
6. Ask the students what they think will happen when an egg is placed in the freshwater and when
an egg is placed in the saltwater. Will they both float? Will they both sink? Will one sink and one
float?
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Density Demonstration: Floating Egg
Saturday Science Club
7. Have them gather around the two containers as the eggs are placed in the water. The egg should
sink in the freshwater container, and the egg should float in the saltwater container.
8. Explain why the freshwater (tap water) egg sinks and the saltwater egg floats. Ultimately, the
saltwater is more dense than the freshwater because of the added salt. Because the egg is more
dense than the tap water, it pushes away the water particles to make space for itself and sinks
down to the bottom of the container. However, because the other egg is not as dense as the
saltwater, the saltwater can hold the egg up, instead of letting the egg sink down to the bottom.
9. Relate these results to the question about humans floating in the ocean versus floating in a swimming pool. The salty ocean water is more dense than the water found in a swimming pool, so it
is easier for someone to float in an ocean than in the swimming pool.
10. Ask the students a more general question: why does anything float? An object will float in a
liquid if the object's own density is less than the liquid's density, and it will sink in a liquid if its
own density is greater than the liquid's density.
References and More Information
1. https://explorable.com/salt-water-egg-experiment
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