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Infant Incubator Lesson 4

What happens when chemicals combine?

Student Sheet

Teacher Answers

Estimated class Time:

Two 40 minute class periods


What happens when chemicals combine?


  • 100 mL 30% Hydrogen Peroxide
  • 10 g Potassium Iodide 
  • Erlenmeyer Flask (250 mL or larger)
  • Water
  • Clear dish soap
  • Thermometer (Infrared is best)
  • Video recording device (phone, ipad, etc.)


Lesson Level Learning Objectives:

  • MS-PS1-2: Develop models before, during and after substances are combined. 
  • Asking questions about what happens when substances are combined. (Cause and Effect)


  • Students will observe a demonstration of a chemical reaction (elephant toothpaste) that has a temperature change, a production of gas, and a change in volume.
  • In small groups brainstorm related phenomena (Examples may include: coke and mentos, snake fireworks, baking soda and vinegar, shaking a soda, water rocket) and explain why it is related. 
  • Students write new questions on the post-it notes that they have about the phenomenon and discuss and post them on a DQB in the classroom.

What we Figured Out: 

  • When we combined the crystals and the water, it did not change. There was not a reaction. 
  • When we combined the crystal water and the unknown substance it changed.
  • It fizzed, bubbled and rose up.
  • It changed colors.
  • It got hot.

Questions we still have:

  • What are the substances that  were combined?
  • Why does it have all of those changes?
  • Why was the flask warm?
  • Why did it change colors?
  • How/why does it foam up?
  • Why did it react slowly?
  • Why did it stain skin?
  • Why didn’t it stain the glass?
  • Does temperature affect color?
  • Does the amount of substances used matter?
  • Is it foam or bubbles?
  • What is foam?
  • Does the foam/bubbles dissolve or evaporate?
  • Where did the liquids go?
  • How did the clear liquids become a yellow foam?
  • Why did the crystals in water become cold?
  • What would happen with more/less ingredients?


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