Science in the Park - Exothermic Reactions

This week - we are focusing on exothermic reactions!  These are reactions that produce heat that the kids can feel!

"Elephant Toothpaste" Experiment

This experiment is called "elephant toothpaste" because the foam that is made is supposed to look like toothpaste that would work for an elephant.
Materials:
Yeast
Warm water
Dish detergent
Food Coloring
Plastic water bottle
Hydrogen Peroxide (3% from the grocery store is fine)
Tin trays (to control the mess!)

How to:
Dissolve the yeast in the warm water - about 2 tablespoons of water for every teaspoon of yeast.
Add the peroxide (about a half cup), a squirt of dish detergent, and a few drops of food coloring to the water bottle.
Add the yeast/water mix to the bottle.
The mixture will foam and pour out of the top of the bottle and into the tray.
Ask the kids to touch the bottom of the bottle - it is warm!

The Science:
The hydrogen peroxide naturally breaks down into water but the yeast speeds up this decomposition!  The yeast acts like a catalyst, decomposing the hydrogen peroxide into water and oxygen which is why the reaction is bubbly and foamy!

Hot Ice Experiment

This experiment creates a supercooled liquid that can quickly turn to solid and gives off heat in the process!

Materials
Baking Soda
Vinegar

How to:
Put 4 cups of vinegar in a sauce pan.  Slowly add 4 tablespoons of baking soda (it will fizz).
Heat until boiling and then keep cooking it until most of the water has boiled away and a film is left on the solution.
There will be foam on the sides of the saucepan, scrap this off and save it.
Once about 90% of it has evaporated, remove it from the heat and place it in an ice bath or in the fridge until it cools. 
Once cool, it should be in a liquid state.  Add a little bit of the foam that was scrapped off earlier and the hot ice will crystallize turning into a solid!  In the process it gives off heat!

The Science:
The boiled down vinegar and baking soda mixture is a supercooled sodium actetate solution.  When the solid sodium actetate and the liquid version mix, it causes the liquid to crystallize and give off heat.  This is what is inside the hand warmer packets!

Enjoy!