A great demo that leads to lots of discussion!

Your students will LOVE this chemical reaction! Pair it up with some excellent discussion AND an introduction to the periodic table and states of matter, and you have a great way to catch their interest!

Activity: Elephant Toothpaste

(there are many recipes for this on-line - I use Steve Spangler's kid friendly recipe so that the ingredients are easy to find and students can touch it!)

Materials:

• hydrogen peroxide (regular strength - one bottle is enough for a demonstration with 2 200 mL sized graduated cylinders or 2 tall bottles)
• yeast (I buy the packets and use one section of the 3 pack)
• warm water (make sure it isn't cold or hot - warm is best)
• Dawn dish soap (any really bubbly dish soap is fine)
• food colouring
• spoon, 2 graduated cylinders (250 mL size) or tall bottles, beaker for preparing the yeast
• large flat tub that will hold the run-off
• poster of the periodic table (not necessary but kids love it)

Safety Notes:

Safety goggles should be worn during the demonstration in case of accidental splashes and to set a good example for future experiments! Plus, they look COOL! Also, hydrogen peroxide is labelled as poisonous so you need to remind students not to taste the toothpaste or the hydrogen peroxide (another good reason to wear the safety goggles!). The food colouring will permanently stain clothing, so I make sure to warn them to move carefully with the toothpaste on their finger if they touch it and not put it on their clothes or the other students clothes. They will need to wash their hands with soap and water if they touch the toothpaste.

Lesson Plan:

1. Set the Stage: Activate Prior Knowledge by asking students questions like:

• Have you ever heard of elephant toothpaste? What is it?
• I usually show the video clip of Steve Spangler on Ellen making elephant toothpaste - it can easily be found on youtube. We then discuss - why do you think that happens?
• I then tell the students that we will be making a student friendly-version of elephant toothpaste that they can easily make at home too!

2. Prepare for and conduct the experiments

• Set up a table with the materials on it and invite the students to come closer to watch!
• Discuss each ingredient, and focus on the state of matter it is in and what it is made up of. I usually start with the hydrogen peroxide. I ask the following questions:
  • Does anyone know what hydrogen peroxide is commonly used for? (put on cuts to disinfect them)
  • Is it a solid, liquid, or gas? (liquid)
  • Why do you think it makes bubbles when it goes on your skin? (answers will vary)
  • Do you know what the chemical name of water is? (H2O - hydrogens (2 of them) and one oxygen). So hydrogen peroxide is H2O2 - write on the board - so the extra oxygen acts as the disinfectant and makes oxygen gas (O2) in the bubbles.
• Pour the packet of yeast into a small beaker.
  • Ask: what is yeast? (answers will vary)
  • What is yeast used for? (it is a microscopic fungus that converts sugar into alcohol and carbon dioxide - it is used to make bread rise)
  • Is it a solid, liquid, or gas? (solid - small spheres)
• Add warm water to the yeast - like about 2 tablespoons or enough to make the yeast thick and soupy but not too watery (don't put in water that is cold or hot - warm is best). Stir it up and students may start to smell a bread-like smell! Set it aside (it needs a few minutes to react)
• Set up the 2 graduated cylinders in a tub that will hold the elephant toothpaste when it comes out over the tops of the cylinders. Pour hydrogen peroxide in to about half of the graduated cylinders. Then add some food colouring - 1 or 2 drops is lots per cylinder. Then add a squirt of dish soap.
  • Ask: What do you think the dish soap will do? (it will capture the bubbles of oxygen gas that will be released once the yeast and the hydrogen peroxide react)
• Get the students ready to watch! Put on your safety goggles to model good safe science, and pour half of the yeast into each graduated cylinder! Watch the eruptions!
• Discuss what happened - see the link here from Questacon for the how to video and explanation of the reaction - https://www.questacon.edu.au/outreach/programs/science-circus/videos/elephants-toothpaste
• In grade 6, students don't really need a detailed explanation - I focus on the states of matter involved and the formation of a gas, which will happen in future experiments and leads into the learning that will happen about properties of air and gases in the flight unit for grade 6.

Extensions:

• This lesson leads into the Solid, Liquid, or Gas activities in the next section.