Earth & Space - Changing materials - Mixing & Separating - P5G12 - ES-C3.1

Learning outcome

When some materials are mixed they are changed completely.

1. Cement is not an ideal substance to be using with children in a classroom situation since it is a very fine powder, easily inhaled and contains lime which is an unpleasant chemical. See Safety Data Sheet.

As an alternative you could use icing sugar and water which although not a chemical reaction could be a suitable substitute. The children could investigate what proportion of water to icing sugar is needed for icing which will pour onto a pretend cake but not run off the sides.

If you wish to use cement, check with Health and Safety for suitable precautions.

2. When soda and vinegar are mixed there is a violent fizzing reaction which produces bubbles and expands the mixture so that it may run down the outside of the container (useful with red dye for simulating volcanoes!) An interesting and perhaps the tidiest way to do this demonstration would be to put vinegar into a small fizzy drink bottle until it is about 1 cm deep. Put 2 teaspoons of baking powder (soda) into a balloon using a funnel. Stretch the neck of the balloon over the neck of the bottle taking care not to release the powder out of the balloon. Now lift up the balloon so that the powder runs into the bottle. Shake the bottle and see what happens.

When vinegar and soda are mixed they release carbon dioxide gas which fills up the balloon!

For other changes try adding salt or sugar to hot water. Keep adding more and more until no more grains will dissolve. This is called a saturated solution. To show that this is reversible, leave some of the solution in an open petri dish until all the water has evaporated and you should see sugar/salt crystals left.