We have now completed our sequence of science lessons about the properties and changes of materials. We have learnt about reversible and irreversible changes – we were amazed to discover that dissolving a solute in a solvent can actually be reversible. To test this, we heated some salt solution over a candle; eventually the water evaporated, and the salt was left behind. Observing the irreversible, chemical reaction between vinegar and bicarbonate of soda was great fun! There were so many bubbles that the cup over-flowed. The bubbles showed that a new material (carbon dioxide) had been produced meaning that we had observed an irreversible change.