There’s a reason you’ve never seen a witch on Food Network: they’re horrible chefs! Every last one of them. They intentionally put disgusting things in their recipes. This experiment will guide you through a classic witch recipe that includes items that you probably already have at home, but never once thought belonged in the same vessel. Witches also tend to be pretty messy in the kitchen, so be prepared for some clean up!

3% Hydrogen peroxide - 125 ml

Clear, empty bottle - 500 ml

Liquid dish soap - 1 tbsp

Warm water - 3 tbsp

Dry yeast - 1 packet (1 tbsp)

Measuring spoon - 1 tbsp

Small bowl

Mixing spoon

Baking sheet

Liquid measuring cup

Small funnel

Food colouring - 10 drops (optional)

3. Using a funnel, add the hydrogen peroxide, dish soap, and food colouring to the water bottle and gently swirl to combine. Be sure not to mix too vigorously as to avoid making bubbles.

Prep time: 10 min

Active time: 5 min

Observation time: 5 min

1. Add the warm water and dry yeast to a small bowl and mix until dissolved. Do not use the measuring spoon to mix.

2. Set the yeast mixture aside for 5 minutes. If after 5 minutes, the yeast mixture has begun to foam, you can proceed to the next step. If there are no bubbles forming, discard this mixture and try again with fresh yeast.

5. Quickly pour the yeast solution into the hydrogen peroxide solution and remove the funnel.

1. Why is it important to use warm water and not hot water?

2. Why do you need to check that the yeast bubbles before adding it to the hydrogen peroxide mixture?

3. Why does the reaction get warm?

When the yeast mixture is added to the hydrogen peroxide solution, the bottle quickly fills with foam and overflows. By placing your hand over the foam, you can feel the heat coming off of it.

If your reaction did not foam, make sure that your yeast is not expired and that you are using warm – not hot – water.

All chemicals are made of building blocks, called atoms, that are bound together by chemical bonds. The chemical structure of water (H2O) is very similar to that of hydrogen peroxide (H2O2). The only difference between the two is that hydrogen peroxide has an extra atom of oxygen weakly bound to it.

Yeast is a living organism. It’s a type of fungus, like mushrooms, and contains an enzyme called catalase. Enzymes are proteins in living things that help to speed up chemical reactions. When catalase is mixed with hydrogen peroxide, it

breaks the bond between the weakly attached oxygen atom and the remainder of the hydrogen peroxide molecule, and rearranges the 3 remaining atoms. This produces oxygen gas and water. As oxygen gas is released, it is trapped by the dish soap, creating bubbles.

oxygen

Yeast isn’t the only living organism that has catalase in it – so do you! Hydrogen peroxide is an unwanted byproduct of chemical reactions that happen in humans. It can spontaneously break down into reactive molecules called hydroxide radicals which can damage DNA in healthy cells and tissues. Catalase in human liver cells works to prevent DNA damage by converting hydrogen peroxide to water and oxygen gas to prevent the formation of hydroxide radicals and keep you healthy.

There are several things that you can change in the materials and procedure above that can have a dramatic effect on the outcome of this reaction. Try one of the following options and compare your results to what you observed following the experiment as written above.

1. Increase the concentration of hydrogen peroxide to 35% and replace yeast with potassium iodide (you can find this at most health food stores or pharmacies). How do the amount of foam produced and the rate of the reaction change? ***
2. Change the size of the opening at the top of the reaction vessel. If you use a cup or bowl with a wider opening, how does the outcome differ compared to using a water bottle with a smaller opening?

*** Make sure that you are wearing gloves and appropriate eye protection as hydrogen peroxide can be irritating to the skin and eyes at any concentration, but more so at higher concentrations. Adult supervision is recommended for younger learners.