Endothermic & Exothermic Reaction Examinations

Using Household Items to Help Kids Explore Endothermic and Exothermic Reactions

Ideas or Inquiries

Learning about the properties of heat through chemical reactions doesn’t have to need a huge laboratory and scary ingredients! Testing the concepts of endothermic and exothermic reactions can be as simple as finding supplies in your kitchen and medicine cabinet.

Vocabulary

Reaction, hydrogen, vinegar, baking soda, CO₂, H₂O, O₂, H₂O₂, exothermic, endothermic

Supplies

• Hydrogen peroxide 3% (the kind you buy in the drugstore)
• Yeast
• Baking soda
• Vinegar
• Tiny scoops & spoons (about ¼-ish teaspoon) – if you have them. Otherwise, adult help in measuring might be needed
• Pipettes 

Directions

1. For each child, put a small scoop of baking soda in one hand, yeast in the other.
2. Using a pipette, put a couple drops of vinegar in the hand with the baking soda, and a couple drops of the 3% HP in the hand with the yeast. (ONLY use the 3% in this activity, any stronger percentage could irritate the skin of our littles!)
3. Ask the child about the different sensations (Baking soda & vinegar will be cold; HP and yeast will be warm).
   • Baking soda & vinegar is an Exothermic reaction
     • “Exothermic” means that it releases heat – it feels warm.
   • HP & yeast is an Endothermic reaction
     • “Endothermic” means that it absorbs the heat from its surroundings – feels cold.

What’s happening? What are the take-aways?

Yeast & HP:

When hydrogen peroxide breaks down, it turns into oxygen (O₂) and water (H₂O). Normally this breakdown happens very slowly. But the reaction could be done faster by adding a catalyst. Yeast is an organism that contains a special chemical called catalase that can act as a catalyst to help break down hydrogen peroxide. Catalase is present in almost all living things that are exposed to oxygen, and it helps them break down naturally occurring hydrogen peroxide. 

This means that if you mix yeast with hydrogen peroxide, the hydrogen peroxide will rapidly break down into water and oxygen gas. 

Baking Soda & Vinegar:

Baking soda and vinegar react chemically because one is a base and the other is an acid. Baking soda is a basic compound called sodium bicarbonate. Vinegar is a diluted solution that contains acetic acid. 

The baking soda and vinegar reaction is actually two separate reactions:

• The first reaction is the acid-base reaction. When vinegar and baking soda are first mixed together, hydrogen ions in the vinegar react with the sodium and bicarbonate ions in the baking soda. The result of this initial reaction is two new chemicals: carbonic acid and sodium acetate. 
• The second reaction is a decomposition reaction. The carbonic acid formed as a result of the first reaction immediately begins to decompose into water and carbon dioxide gas (CO₂). Just like carbon dioxide bubbles in a carbonated drink, the carbon dioxide (that formed as the carbonic acid decomposed) rises to the top of the mixture. This creates the bubbles and foam you see when you mix baking soda and vinegar.