In Science, we have been learning about the properties of materials. This lesson was all about irreversible change. The children took part in class experiments using reactants, bicarbonate of soda and distilled white vinegar, to create chemical changes and form a new product, carbon dioxide. The children saw the carbon dioxide gas appear using an air tight seal by attaching a balloon around the neck of a plastic bottle. The only place the gas could go was into the balloon. The children watched the balloon blow up in front of their eyes as if by magic but they learned that this was the product formed from the reaction between the two materials used. Carbon dioxide is a very useful gas. It is dissolved in liquids to create fizzy drinks, it is used to cool food on aeroplanes and trains and it is used in fire extinguishers to put out fires.
We also made a plastic called Casein by mixing warm milk and vinegar together. The two reactants curdle and separate into clumps of solids floating in the thin watery liquid. The solid that is made is a new material which is Casein. Casein plastic can be formed and moulded into shapes. It was commonly used in the 1900's up until about 1945. It was used to make buttons, beads, jewellery, fountain pens, the backings for hand held mirrors and fancy combs.