When a chemical reaction occurs, two types of changes happen. These types of changes can be classified as either physical or chemical. Chemical changes produce an additional component, such as a release of a new chemical, production of rust or a change in temperature or colour. Third-graders will get a better understanding of what a chemical change of matter is by doing hands-on activities and experiments.
Rusting Steel Wool
Take a small piece of steel wool and place it in the bottom of a beaker. Pour 1/3 cup vinegar over the steel wool and let sit for approximately 15 minutes. Measure the temperature of the wool to show that the wool is exuding heat. Remove the steel wool and have students observe it. Rust will begin to form on it as the acid eats away at the steel wool.
An experiment easy to complete and observe is oxidation with an apple. Slice an apple. Give a slice to each student. Have students observe the original colour of the apple slice. Wait approximately 10 minutes and have the students observe the colour of the apple again. The colour will have changed from white to brown. This is from the reaction of the enzymes in the apple with oxygen.
Rip up purple cabbage leaves and place the pieces into a zip-lock bag. Pour 3/4 cup of warm water into the bag and zip the bag up. Shake the bag for approximately three minutes or until the water has turned dark blue. Place 2 tbsp of dark blue water into two separate cups. Add one drop of vinegar to one cup and one drop of liquid detergent to the other cup. Swirl the cups. Observe the colour changes in both cups due to the addition of acids and bases to the blue water.
To test for the release of a gas, fill a clear glass with one cup of water. Place 1/4 cup vinegar in the glass and stir. Add 1 tsp baking soda to the glass. As soon as the baking soda is added, toss in five popcorn kernels. The combination of vinegar and baking soda produces carbon dioxide, which is visible in form of bubbles. The popcorn appears to be dancing because of the release of carbon dioxide.