Here’s a fun Halloween twist on a classic science experiment for kids! Make your own Jack O’Lantern Lava Lamp. This is not a true lava lamp, but rather a chemical reaction. The bubbles given off by the reaction create a really cool lava lamp effect!

Turn your lava lamp into a Jack O’Lantern for a fun fall science experiment.

Jack O'Lantern Lava Lamp in a jar.

I highly recommend this lava lamp science experiment because:

  1. The materials are SO simple! Pick them up when you get groceries. And…
  2. You can repeat it over and over without making a mess or even having to refill the jar!

Supplies Needed for a Jack O’Lantern Lava Lamp:

  • Clean empty jar – we started with an 8 oz mason jar, but quickly upgraded to a large spaghetti sauce jar.
  • Red and yellow food coloring
  • Vegetable oil or baby oil
  • Alka Seltzer tablets
  • Black felt
  • Hot glue gun

Step 1: Cut a Jack O’Lantern mouth and eyes out of black felt. Glue them to your jar with hot glue.

(When you finish the experiment, you can actually peel the felt right off the jar if you want! You won’t be able to tell it was ever there.)

Step 2: Fill your jar about 1/3 full with water. Add red and yellow food coloring to make the water orange.

It will take MUCH more yellow food coloring than red. If you add equal amounts, it will look red.

Step 3: Fill the jar the rest of the way with oil – either vegetable oil or baby oil.

Baby oil costs quite a bit more than vegetable oil. We used some in our first jar because we had it on hand, but then switched to vegetable oil for our larger jar.

Step 4: Drop in an Alka Seltzer tablet! The bubbles created by the Alka Seltzer dissolving in the water will float up through the oil, making a lava lamp effect.

Jack O'Lantern Lava Lamp

This is so much fun to watch! As I mentioned earlier, after the bubbles die down, you can just drop in another Alka Seltzer tablet. We made it through at least 10 tablets without changing the water and oil.

The Science Behind the Lava Lamp

Alka Seltzer tablets contain sodium bicarbonate (baking soda), citric acid, and aspirin (a pain reliever). In the tablet, the baking soda and citric acid can’t react with each other. When you drop the tablets into water, the citric acid reacts with the baking soda to form sodium citrate (which neutralizes stomach acid when you drink it), water, and carbon dioxide bubbles. We’re just interested in the carbon dioxide bubbles because they form the cool lava lamp effect!

When you mix water and oil in your jar, the oil separates and rises to the top. Oil and water won’t mix since water is made up of polar molecules, or molecules that have uneven electrical charges, and oil is made up of non-polar molecules. Oil is also less dense than water, so the water sinks to the bottom and the oil ends up on top.

When you drop an Alka Seltzer into your lava lamp, it won’t react with the oil. It drops down to the water level and begins to bubble. The carbon dioxide bubbles rise up through the oil because they are lighter (less dense) than both water and oil, and they take some of the colored water along with them. Once the bubbles pop at the top, the colored water drops back down again.

So cool! We love science!

Need more Fall Science and STEM ideas?

Here’s a collection of The Best Fall STEM Activities for Kids.

Jack O'Lantern Lava Lamp

4 Comments

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  1. Rosemary Oct 5, 2020

    How long does the lava lamp last after the seltzer is added to it please?
    Thank you

    Reply
    1. Sarah Oct 5, 2020

      One tablet lasts just about a minute or so. But you can add more tablets to keep it going!

      Reply
    2. Brenda Carpenter Oct 7, 2020

      Can I use Canola oil in place of vegetable oil?

      Reply
      1. Sarah Oct 8, 2020

        I haven't tried it, but I would think that would work just fine!

        Reply
      2. Sarah Oct 13, 2020

        Can you use Polident instead of Alka Seltzer?

        Reply
        1. Nancy Oct 20, 2020

          Ok to use dental cleanser fizzies instead of alkaline seltzer

          Reply
          1. Sarah Oct 21, 2020

            That would probably work! I would try it first before doing it with a group or class!

            Reply

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