posted by Gina
Age Range: 5 and up.
This is a nifty (dare we say groovy?) experiment that kept Larry the Cat amused for several hours today – ensuring its success with your kiddo.
You Will Need:
- An empty bottle – those schmancy designer water bottles work well (as do empty – erm – adult bottles, as pictured above), but any empty, clear bottle will work just fine
- Food coloring
- Alka-Seltzer tablets
1. Fill the bottle between a-little-over-half to 2/3 full of oil.
2. Fill the bottle the rest of the way with water, leaving an inch or so on top.
Watching the water settle is fascinating on its own.
3. Add 10 or so drops of food coloring.
You’ll see the drops travel through the oil and settle into the water, coloring the water but not the oil. Neat!
4. Drop in a piece of Alka-Seltzer … and watch the magic.
Continue to drop in Alka-Seltzer as the bubbles die down to keep the Lamp moving.
- Waiting for the oil and water to really settle makes the Lava Lamp effect work way better. However, rushing the process will give you some interesting effects:
- Breaking the Alka-Seltzer into smaller piece – four to five a tablet – will keep your Lamp from getting cloudy.
Why does this work?
It’s all about density. What is density? Imagine you have two items that are the same size, but have different weights. The one that weighs more is more dense – meaning it has more matter packed into it. Those “Will this float?” experiments we’ve all done are merely exercises in determining which objects are more dense than water.
When you first mix the water and the oil, the water sinks to the bottom and the oil floats on top. That’s because water is more dense than oil.
The Alka-Seltzer contains contains citric acid and sodium bicarbonate (baking soda). Those two ingredients react in the water, making a fizz – tiny bubbles of gas. This gas is less dense than the oil, so bubbles of the now-colored water is carried with the gas through the oil. Amazing!
Curriculum Connection: Science!
- Here are some more fun kitchen experiments with density – including making vinaigrette and layered drinks.