DIY Lava Lamps

Activity 3: DIY Lava Lamps
Students will understand density, chemical reactions and simple circuits by creating a nifty take home, reusable lava lamp.

Set-up:
Every student will need two LED lights, two coin batteries, and a water bottle. Keep the water, vegetable oil and food coloring at a communal table so that you can track the amount each student is using. Electrical tape can be distributed to the tables to share.

Demo and discussion:
Although building lava lamps seems like a lighthearted and primarily fun activity, there is a lot of science behind the activity. First, you want to discuss with your students the concept of density. Simply stated, density is how compact the matter is in a particular substance. More compacted matter
That’s because Houston crams and compacts more people per square mile than Crosby or Liberty. On the other hand, New York City is the most populated city in our country as well as the most densely populated. That’s because Houston has a much larger area in which to spread out. When teaching chemical density, people often allude to a substance’s tendency to sink or float. This is technically incorrect. A much better analogy is whether a substance mixes with another substance or not. In the case of the lava lamps three different liquids are used – water, vegetable oil and food coloring. Oil is less dense than water so it does not mix with the water. Food coloring is denser than water, so it drops through the oil and settles in the water mixing with it. The chemical reaction is a result of dropping the Alka-Seltzer into the water. When Alka-Seltzer tablets are dissolved in water, bicarbonate forms (from the sodium bicarbonate), which in turn reacts with hydrogen (from citric acid) to form water and carbon dioxide gas. As the carbon dioxide gas bubbles float up towards the oil they get trapped in the denser oil and begin to sink back down. Eventually all the gas dissipates away and the reaction stops. To make the
We want to make sure that any subsequent groups that you serve are not shorted. Each student can have a pack of Alka-Seltzer, which is enough for eight reactions (each tablet needs to be quartered). Make sure they do not dump all eight sections into the lava lamp at once, and make sure they wait until the reaction is over before adding a new tablet.

Reflection:
Make sure the students take time to write in their scientific journals any observations they notice when conducting their experiments. You can prompt them by asking them to describe density, chemical reactions or simple circuits.

Clean-up:
Reset supplies before each new group