clear plastic cups
dixie cups
oil
water
alka seltzer
food color
Concept: When Alka Selzer and water mix it casues a chemical reaction that makes a gas. The gas moves slower through the oil than the water (density) causing the lava lamp effect.
Procedure: Pre pour 1/4 of clear plastic cup with oil. Have students pour Dixie cup of water into oil. Have student observe how the oil and water react to one another (don't mix). Ask student whic one is heavier. The one on top (oil) or the one that sank (water) to the bottom. Add 4-5 drops of food coloring. Observe. Explain that the food coloring is coated in oil. Therefore, it stays suspended in the middle since ild and water don't mix, until is is coated with enough oild to make it heavy enough to sink. Let student drop in an Alk Selzter tablet. Observe from the side of the glass. Watch as the Alka Seltzer forms bubbles of gas that move slowly throug the water.
Extension: Use salt instead of Alka Seltzer. Try different temperatures of water. Use two different colors of food coloring to learn color mixing.
Application to the Real World: A real lava lamp works due to a process called convection. As the wax heats up, it expands, causing less density. This makes it less dense then its surronding liquid causing it to float. When the wax reaches the top of the lamp, away from its heat source, it cools down. This causes the wax to contract and become more dense than its surrounding liquid leading it to sink and the cycle then repeats.
