Density- Floating and Sinking Eggs (Audrey Benson)

Author

Audrey Benson

Principle(s) Illustrated

• Eggs

• Density

• Mass

• Volume

• Concentration

• Buoyancy

• Water

Standards

• DCI: PS1: Matter and Its Interactions

• DCI : Motion and Stability: Forces and Interactions

• CCC: Structure and Function

• CCC: Cause and Effect

• SEP1: Asking questions and defining problems

Questioning Script

Prior knowledge & experience:

Students should have a background in the interactions of matter. They may have even heard the word density before.

Root question:

Why does one egg sink, one egg float, and one egg hover?

Target response:

The solutions that the eggs are floating in are different. The sinking egg is in regular water. The floating egg is in concentrated salt water. The hovering egg is in a mixture of fresh water and salt water. The egg floats when the solution is more dense than the egg. The egg sinks when the solution is less dense than the egg. The hovering egg is at neutral buoyancy, so its density matches that of the solution (or it is resting on top of a layered solution).

Common Misconceptions:

Students may think that the eggs are different. They usually assume that the eggs are hard boiled.

Materials & Procedures:

• Eggs

• Water

• Measuring cup

• Beakers

• Table salt

• Soup spoon

1. Prepare a very salty solution. It will take a long time for the salt to dissolve, so keep stirring! Heating up the water helps. When the salt has dissolved, place an egg into the water. It should float.

2. Put another egg into plain water. It should sink.

3. Make a third solution that makes the egg hover. One way to do this is to layer the water. Fill the beaker halfway with salty water, then insert a spoon along the side of the beaker and gently pour the fresh water onto the salt water. After you have layered the water, insert the egg. It should float on top of the salt water layer.

Photographs and Movies

Floating Egg Experiment Video

References

Salty Science: Floating Eggs in Water