Year 6 have been learning about reversible and irreversible changes.
We used bicarbonate of soda, vinegar, a microwave and chocolate to demonstrate an example of each type of change.
The children predicted that if we put chocolate in the microwave, it would melt because "most solids can melt". Some children also thought that "the chocolate might get burnt" (they were right!). They thought that melting chocolate was a reversible change because you could wait for it to become solid again as it cooled. Some also observed that the chocolate would cool more quickly in the fridge and that "the freezer would be even quicker".
As we concluded that the chocolate could change state from solid to liquid and back again, this was a reversible change.
It was harder to predict what would happen when we mixed bicarbonate of soda and vinegar. Some people thought "it will fizz" and some thought "it will cause a chemical reaction".
After observing the demonstration, we were able to explain it in more detail. "The vinegar is an acid which mixes with a base" said one child. "If you put more of it in, it will have a bigger reaction" observed another. Eventually, we were able to work out that "it will not be reversible because when you mix it, it will become something new."