Super Cold Bag with Science Visitors

We had special visitors today come and see how we 'do science'. These visitors are teachers who are on a Science Leadership course with the Royal Society. They are from all over New Zealand.

The experiment we did today had a fantastic chemical reaction - one that none of us guessed would happen. The photos tell a bit of the story.


Try this at home - here's what to do:-

Materials:

 · Citric Acid

 · Baking Soda

· Tap Water

· Zip lock bag (15cm x 10cm)

· Measuring cup

 · Plastic teaspoon

Perform this experiment over a kitchen sink or outside. There is a small chance the zip lock bag will burst making a wet mess!

What to do:-

Put one level teaspoon of citric acid in a zip lock bag

 Put one teaspoon of baking soda in the same zip lock bag. And shake the bag gently to mix the two chemicals.

Fill up the measuring cup with cold tap water (about 30ml).

Carefully place the water in the bag and zip the bag shut.

 Tip the cup over in the sealed bag and watch! Not only does the bag blow up, it also becomes super cold! So don’t forget to feel its temperature.

What’s happening and why: Mixing citric acid, baking soda and water together causes a chemical reaction. The new chemical that is made is carbon dioxide gas. This gas fills the bag and causes it to blow up. You’ll also notice the bag drops in temperature as part of the chemical reaction.