14: Handwarmers

You may have come across small packages in camping shops which help to warm your hands in winter. You may also have used a pack to heat up canned food. These bags rely on two chemicals reacting and heating their surroundings in the process. This is an exothermic reaction. Have a go at making your own heat pack.

What you will need

weighing balance
150cm3 beaker
250cm3 measuring cylinder
thermometer
calcium chloride - 8 mesh 		stirring rod
spatula
2 sealable freezer bags - large and small
eye protection

What you do

YOU CAN MAKE A HEAT PACK AS FOLLOWS

  1. Eye Protection
    Add approximately 117cm3 of distilled water to the large bag. Place the bag inside a beaker to keep it upright.
  2. Irritant
    Add 4.5g calcium chloride to the small bag. Partially close the bag leaving some of the seal open.
  3. Place the small bag containing the calcium chloride into the large bag.
  4. Seal the large bag.
  5. Heat Produced
    Activate the heat pack by squashing the inner bag to release the calcium chloride and shaking the water and calcium chloride together. Observe what happens.
YOU CAN INVESTIGATE THE BEST WAY OF MAKING A HEAT PACK AS FOLLOWS

  1. Eye ProtectionIrritantWarning
    Measure out 100cm3 distilled water into a beaker.
  2. Measure the temperature of the water.
  3. Weigh out 10g of calcium chloride.
  4. Add the calcium chloride to the water, stirring occasionally.
  5. Record the temperature of the solution.
  6. Repeat 1-5 for different masses of calcium chloride.
  7. Draw a graph of the highest temperature against the mass of calcium chloride used. Use your graph to decide how much calcium chloride you need to make a heat pack that heats up to 40°C-50°C.
Eye Protection
eye protection must be worn

Irritant
IRRITANT
calcium chloride

Warning
HEAT PRODUCED

Warning
if outer pouch breaks flush the contents down the drain


Contents