A Lesson on Density: Making a Lava Lamp

1. Fill a jar ½ filled with water.

2. Fill the jar to 2/3 filled with vegetable oil. Observe.

3. Add a few drops food coloring. Observe. Then mix and observe.

4. In teaspoon amounts add salt. Observe.

5. When salt has settled on bottom of jar, place a golf ball into the jar. Allow to sit for at least an hour. Observe.

Explanation: Oil is less dense than water so it will settle on top. Adding food coloring will initially show it settles on the oil mixing shows it won't mix with the oil but with the water. Salt is a solid and when it's place into the jar, the sugar will fall to the bottom of the jar because it's density is greater than both the oil and the water. When the salt falls it will take some oil to the bottom of the jar but because of oil's density, it will rise back above the water (thus the lava lamp affect). Setting the golf ball into the jar and allowing the entire mixture to sit for at least an hour allows time for the salt and water to mix, raising the density of the water and thus causing the golf ball to float in the salt water.