Question

13 (xiv) Against each change described below, write P for physical change and C for chemical change.

The milk turned sour.

Answer 1

• The milk turned into sour is classified as a chemical change.
• This is because it results in the production of sour-tasting lactic acid. In this process, new substances (lactic acid) have been formed and it is an irreversible change.
• Chemical changes are those in which new substances are formed. The properties of the new substances formed are very different from the original substances.
• Chemical changes are usually irreversible.