Gather your students or audience around a large, flat table so the experiment can be seen by everyone watching.
Fill a regular, tall drinking glass or a graduated cylinder to two-thirds with warm tap water.
Ask your watching audience what they think will happen if you placed a regular egg into the water. Encourage your viewers to raise their hands if they think the egg will float.
Carefully lower the egg into the water. Remove your hands so your audience can observe the egg, which will sink in this condition, though not necessarily to the bottom of the glass.
Remove the egg from the water and place to one side. Add three tablespoons of salt and stir it into the water until the salt is completely dissolved.
Ask your audience for their hypothesis before repeating the egg-lowering process. Observe as the egg floats on the water's surface. Explain that this is occurring because the salt water is denser than regular tap water.