ALL ABOARD: WE’RE GATHERING STEAM
Today’s STEAM activity looks like a real ’70s lava lamp and teaches kids about the relative densities of oil and water. It’s also mesmerizing to look at!
- Small clear cup or jar
- Light coloured or clear oil
- Food colouring
- Effervescing antacid tablet (such as Alka-Seltzer)
- Fill your jar or cup about two-thirds’ full with oil.
- Add water until the liquid is about 1 inch from the top of the jar.
- Add 5 to 10 drops of food colouring.
- Break your antacid tablet into 4 pieces. Start dropping the pieces into the jar one at a time, watching the bubbles grow with each addition. The food colouring will eventually get mixed into the water by the turbulence from the bubbles.
- Enjoy watching the slow moving bubbles. Afters the bubbles stop, let the oil and water separate again and you can add another tablet and start the lava lamp show all over again!
*Note: You can repeat this experiment over and over using the same jar of oil and water. You do not have to dump and start again each time you want to do it. Just let the antacid tablet completely dissolve and all the bubbles stop, and then it’s ready to go again.
Remember: when you are finally ready to dump the lava lamp contents, don’t dump it down your drain! Please responsibly dispose of your oil, check your local waste disposal guidelines on how to properly discard oil.
This activity supports the development of the following STEAM skills:
Science: Oil and water don’t mix. Water is polar and oil is non-polar and hydrophobic, meaning it repels water. Oil is less dense than water, so when they are combined they immediately separate and their difference in densities makes the oil float on top of the water. You see this separation at the start of the experiment when you add water to the oil in the the jar, and also when you add the food coloring.
The food colouring is water soluble so it only mixes with the water and not the oil. When you add it to the jar, you will see it sink down below the oil and sit on top of the water until the bubbles from the antacid tablet mix it into the water.
As the effervescing antacid tablet dissolves in the water, it releases carbon dioxide bubbles. These bubbles are lighter than both liquids so they push from the bottom of the jar towards the top, taking blobs of water with them through the oil. The carbon dioxide bubbles break when they hit the surface, then the water falls back down to the bottom of the jar due to its heavier density.