You will notice that the plastic bag becomes a little warmer to the touch. If you can’t feel it, use a thermometer to measure it!  Which one of the following is correct?

1.The plastic bag becomes warmer because the air around the bag is warm.    

2.The plastic bag becomes warmer because the dissolving detergent is taking in heat.     

3.The plastic bag becomes warmer because the dissolving detergent is giving off heat. 

Students from all grades are invited to take their answers to their KCFS teachers for a cool prize.    

How it works 

　When things are mixed together they can make something completely new. This is called a chemical reaction. Some chemical reactions give off heat while others take in heat. Hand warmers give off heat when oxygen reacts with iron powder to make iron oxide, or rust, and with the help of salt. And that’s how hand warmers are able to keep your hands warm on a cold winter’s day!