You’ll need

  • An empty drink bottle with a pop-top lid
  • White vinegar
  • 2 small funnels (optional)
  • Dishwashing detergent
  • A teaspoon of bicarbonate of soda (also called bicarb soda and sodium bicarbonate)

What to do

Warning!

This experiment can get messy! Do it somewhere you can make a mess, like a backyard or laundry. Vinegar can be tipped down the sink, but any unused bicarbonate of soda should be thrown in the bin.

  1. Gather your materials on a flat surface.
  2. Close the pop-top and unscrew the lid from the bottle.
  3. Carefully half-fill the bottle with vinegar. A funnel might help. Add a small squirt of detergent to the vinegar.
  4. Add the bicarbonate of soda to the bottle (you can use a dry funnel to help you do this).
  5. Quickly screw the lid on the bottle and give it a shake to mix everything together.
  6. Place the bottle on a flat surface. Stand back and, within a few seconds, a foamy fountain will shoot out of the bottle!

Questions to ask

Why do you add detergent to the bottle? What happens if you do the experiment again without adding detergent?

What happens if you add less bicarbonate of soda to the bottle?

What's happening

When sodium bicarbonate is mixed with vinegar, it makes a lot of carbon dioxide gas (also written by its chemical formula CO2). When detergent is added, the bubbling carbon dioxide gas makes lots of foam. Because the lid of the bottle is closed, the carbon dioxide gas is trapped inside the bottle. This builds up pressure inside the bottle until, eventually, the pop-top lid is pushed open and a spectacular column of white foam rushes out!

The chemical reaction between sodium bicarbonate and vinegar is a type of acid–carbonate reaction. The acetic acid in the vinegar reacts with the sodium bicarbonate to make sodium acetate (a type of salt), carbon dioxide gas and water.

Show Transcript

Rachel: Hi everyone, my name’s Rachel, I’m from the Questacon Science Squad and today we’re going to make a fountain of foam and a lot of mess.

(Camera pans to the table)

You need:

  • some vinegar
  • a pop-top bottle with the lid,
  • some bicarbonate of soda
  • a teaspoon and
  • some detergent.

Right, first thing you do is pour some vinegar into the bottle about half way. Whoops! Whoop, you need a, quite a still hand to do this.

(Rachel pours the vinegar into the pop-top bottle)

And next step, just a squeeze of detergent, like so.

(Rachel squeezes some detergent into the bottle)

And next, in with the bicarbonate of soda. OK get about a teaspoon’s worth and, hopefully your hands aren’t as shaky as mine, down through the top there.

(Rachel puts a spoonful of bi-carb soda into the bottle)

Screw the lid on and give it a really good shake.

(Rachel screws the lid on to the bottle, gives the bottle a shake as she puts it down the liquid spurts out the top and she SCREAMS!).

Fabulous!

If you want to find out how to make your own fountain of foam, you can visit our Questacon website. See you next time.

Did you know

Sodium bicarbonate is used in some fire extinguishers, known as dry chemical fire extinguishers. These are good for putting out small kitchen fires and electrical fires.