Can a change in colour indicate a chemical change?

Yes, a change in colour can indeed indicate a chemical change.

A chemical change, also known as a chemical reaction, involves the transformation of one or more substances into new substances. This process often results in observable changes, one of which can be a change in colour. For instance, when iron rusts, it changes from a silver-grey colour to a reddish-brown, indicating a chemical reaction has taken place. Similarly, when you cook an egg, the clear egg white turns white, which is another example of a colour change due to a chemical reaction.

However, it's important to note that a change in colour doesn't always signify a chemical change. Sometimes, a physical change can also cause a change in colour. For example, when you heat a metal, it might change colour due to the heat, but this is a physical change, not a chemical one.

Moreover, not all chemical changes result in a colour change. Some chemical reactions may not produce any visible changes at all. Therefore, while a colour change can be a clue to a chemical reaction, it is not a definitive proof. Other signs of a chemical change include the formation of a gas (bubbles), the formation of a precipitate (a solid that forms from a solution), a change in temperature, or a change in properties.

In conclusion, while a change in colour can indicate a chemical change, it is not always the case. It's crucial to consider other factors and signs to determine whether a chemical change has occurred.