Chemistry

Gilla:		Dela:

Video

Materials

• Sand
• 1 tray with raised edge
• 1 small bowl - It should hold about 1 dl (1/2 cup) but not much more.
• Red and yellow food color
• Vinegar
• Baking soda (or baking powder)
• Liquid dish soap
• 1 teaspoon measuring spoon (5 mL)
• 1 tablespoon measuring spoon (15 mL)

Explanation

When baking soda and vinegar come in contact with each other, a chemical reaction takes place where carbon dioxide is formed. The carbon dioxide, which is a gas, is trapped as bubbles in the dish soap and wells out of the volcano.

Common household vinegar, also called distilled white vinegar, consists of about 5 % acetic acid and the rest is water.

Baking soda is also known as bicarbonate of soda. Both are household names for sodium bicarbonate.

If you use baking powder, it is not pure baking soda. It consists of about 30 % baking soda, 40 % some acid (for example cream of tartar) and 30 % some moisture absorbing substance (for example corn starch).

When sodium bicarbonate and acetic acid mix they react and form sodium acetate, water and carbon dioxide. If you use baking powder it also reacts with itself when it comes into contact with water - bicarbonate and the baking powder's own acid react and form a salt (which one depends on the acid) as well as carbon dioxide.

The carbon dioxide is trapped in the dish soap and soap bubbles full of carbon dioxide are formed. The foam also contains the other products of the chemical reactions.

Baking soda and baking powder are both used in baking as leavening agents - substances that make the bread or cake fluffy by adding bubbles of carbon dioxide. Baking soda needs some other acidic ingredient to react with, but baking powder has its own acid.

Experiment

You can turn this demonstration into an experiment. This will make it a better science project. To do that, try answering one of the following questions. The answer to the question will be your hypothesis. Then test the hypothesis by doing the experiment.

• What happens if you use more baking soda (or baking powder)?
• What happens if you use more vinegar?
• What happens if you use more dish soap?
• What can you add to the mix to make the lava thicker and more like real lava?

Variation

If you don't have access to sand, you can make a volcano out of paper shaped like a cone, with the crater bowl standing on something inside the cone so that it reaches the right height. You can also make the volcano from papier-mâché, salt dough or modeling clay.

It is also possible to replace the baking soda (or baking powder) and vinegar with 120 ml (1/2 cup) hydrogen peroxide 6 % and 7.5 ml (1/2 tablespoon) dry yeast. The hydrogen peroxide is poured into a drinking glass that is "baked in" inside the volcano, and then the dry yeast is added while stirring quickly. The gas that's captured by the dish soap is in this case not carbon dioxide, but oxygen.

Gilla:		Dela: