ELEPHANT TOOTHPASTE

Always make your TOOTHPASTE under adult supervision!!!

THIS IS NOT REAL TOOTHPASTE, SO DON’T USE IT ON YOUR TEETH!!!

Materials

• One bottle (200 mL) of hydrogen peroxide (either 6 or 9%) – available in all pharmacies

• Packet or a bag of fast action yeast (one packet or tbsp per reaction)

• Dish soap (any type)

• 1L bottle (if you use smaller or larger bottles, you should adjust the amount of hydrogen peroxide)

• A small measuring jug/cup

• A thermometer (don’t worry if you don’t have one)

• Food colouring (any colours you like!)

• A4 paper or a paper bag plus colouring pens/pencils to make your label

• A tray or plastic box to contain the reaction (you can do it in the sink otherwise)

Procedure

Phase one

AN ADULT SHOULD MEASURE AND POUR THE HYDROGEN PEROXIDE

1. Add 50-60 mL of hydrogen peroxide from the measuring jug and a few squirts of soap to the bottle. Give a good shake for 30 seconds.

2. If you want to, make a label for your toothpaste.

Phase two

3. Wash the measuring jug.

4. Add in one packet/one tbsp of yeast to the jug.

5. Pour some water from the hot tap into a separate cup.

6. Use a thermometer to measure the temperature of the water. It needs to be 40-45^oC to wake up the yeast. If you don’t have a thermometer, get an adult to do this part!

Let your hot tap run for 10 seconds. You should feel the water get hot, but not scalding. If you can keep your wrist in the running water comfortably, then you have the right temperature. This is about the same temperature you would use to proof yeast for baking or warm a baby’s bottle. If you can’t keep your hand/wrist in the water, it’s too hot. If it is too hot, mix about 80 mL of hot and top up with about 20 mL of cold. See this link: https://food52.com/blog/12880-get-the-right-water-temperature-for-yeast-without-a-thermometer

7. Once the water is at the right temperature, fill the jug with the yeast up to about 100 mL. Give a really good stir for 30-60 seconds.

8. Make sure you have no lumps in your yeast solution.

9. Add food colouring to the bottle and give it a good shake for 20 seconds. If you want your toothpaste to have stripes, pour the different colours down the sides of the bottle (hold the bottle at an angle) and don’t shake it!

Phase three

10. Place the bottle inside the box.

11. Stand away from the bottle and add the yeast solution to it as quickly as you can.

12. You should now have your toothpaste!

13. When you want to clean-up, everything you have used can be washed down the sink.

How It Works

Hydrogen peroxide is made up of two different elements: two atoms of hydrogen + two atoms of oxygen (H₂O₂).

Hydrogen peroxide naturally breaks down over time. When this happens, it forms oxygen (O₂) and water (H₂O):

Hydrogen peroxide --> Water + Oxygen

[2 H₂O₂(aq) --> 2 H₂O(l) + O₂(g)]

This happens very slowly.

Imagine the hydrogen peroxide is like a giant rock you are pushing uphill, so you can let it roll down the other side and break into small pieces to form the oxygen and water.

To get the hydrogen peroxide to breakdown into smaller pieces, you need a lot of energy and time to get to the top of the hill.

When we add the yeast solution to the hydrogen peroxide, it increases the speed at which it breaks down.

This means the yeast is acting as a catalyst. Don’t worry if you don’t know that word! All it means is that it speeds the reaction up, to produce water and oxygen much faster than before.

When we add the yeast, we get a shortcut around the hill the rock is being pushed up.

This means we don’t have to push it so far up the hill and we can make the rock break into smaller pieces with less energy and time.

Without the yeast, the toothpaste would still come out of the bottle, but very very slowly.

The more hydrogen peroxide you use, the faster the toothpaste should come out of the bottle.

Why don’t you try the experiment again, but use different amounts of hydrogen peroxide to see what happens?

Useful links

If you want to share a picture of your label or elephant’s toothpaste you can upload them here: https://1drv.ms/u/s!AkBgddt1EMAwga9uH5ewjidUIFYdhA?e=zTG1k0

If you want to know more about catalysts: https://kids.kiddle.co/Catalysis

Our next video will also use yeast. If you want to do some reading about yeast this is a good place to start: https://kids.britannica.com/kids/article/yeast/442746

Ice Cream In a bag!

Always make your ice cream under adult supervision!!!

Materials

2 tbsp sugar (or sugar substitute)

300 mL milk (or milk substitute)

300 mL whipping cream (or substitute*)

1/2 teaspoon flavouring (any flavour!)

Colouring (any colour!)

1 zipper‐top bag

1 large Tupperware box

Ice

Thermometer

2 tbsp sodium chloride (NaCl) as table salt or rock salt

Measuring cups and spoons

Decorations

* https://www.healthline.com/nutrition/heavy‐cream‐substitutes

Procedure

Phase one

1. Add sugar, milk, cream, flavour and colouring to zipper bag. Seal the bag securely. Give a

good shake for 30 seconds.

Phase two

2. Smash up some ice – be careful!

3. Half‐fill the box with ice.

4. Use a thermometer to measure and record the temperature of the ice in the box.

5. Add salt to the box of ice. Give a good shake for 30 seconds.

6. Check the temperature of the box of ice again.

Phase three

7. Place the sealed bag inside the box of ice and salt. Seal the box securely.

8. Shake the box from side to side.

9. !!!!!!!It's best to hold it by the top seal or to have gloves or a cloth between the box and

your hands because the box will be cold enough to damage your skin.!!!!!!!

10. Continue to rock the box for 8‐10 minutes or until the contents of the bag have solidified

into ice cream.

11. Remove the bag, open it, serve the contents into a bowl. Decorate with whatever you want!

12. Open the box and use the thermometer to measure and record the temperature of the

ice/salt mixture.

How It Works

Ice has to absorb energy to melt, changing the phase of water from a solid to a liquid. When you use

ice to cool the ingredients for ice cream, the energy is absorbed from the ingredients and from the

outside environment.

When you add salt, it lowers the freezing point of the ice, so even more energy has to be absorbed

from the environment for the ice to melt. This makes the ice colder than it was before, which is how

your ice cream freezes.

The reason it is better to use rock salt is because the larger salt crystals take more time to dissolve in

the water around the ice, which allows for more even cooling of the ice cream.

Also, the more particles there are, the greater the disruption and the greater the impact on

properties like freezing point depression.

Why don’t you try this experiment with different types of salt and, also, different amounts of salt to

find the perfect recipe!