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Why Does The Egg Float
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Density Paradox

Science Area:  Chemistry
Concept:  Density

Floating Egg

 

Materials:

2 Uncooked Eggs

2 Clear Glasses

Salt – About 10 tablespoons

A Spoon

 

 

Safety Considerations:

Be careful not to spill water on the floor.

Be careful not get salt in your eyes.

 

Discrepancy:

Students will not expect the egg to float.

 

Procedures:

 

Before Students See You:

1.  Fill two glasses half way with water.

2.  Add 10 tablespoons of salt to one, but not the other.

 

When students are present:

3.  Have the students predict what will happen when you drop the eggs in the container.

4.  Place an egg in the glass with water only.                                                                                      

5.  Discuss your observations

6.  Place an egg in the glass with the salt water.

7.  Observe and discuss the results. 

 

Questions:

1.  What did you expect to have happen?

2.  Why do you think happened?

3.  Does salt have weight? 

4.  Why did the weight change in the salt water?

5.  Did adding mass increase or decrease the density of the water?

 

 

Explanation:

 

In the first trial the egg will sink because it is more dense than the water.  When salt is added to the water it increases its density, making it more dense than the water.  You can really jazz this one up if you add a third glass and pour salt water on the bottom and then very carefully funnel regular water on top of the salt water.  When the egg is placed into the glass it will float in the middle between the salt water and regular water.