Which of the following process is a physical change?Select an answerASodium dissolves in waterBIron rustsCIron is magnetisedDMagnesium wire is burnt

The correct answer is A. Sodium dissolves in water. This is a physical change because it can be reversed and it doesn't change the chemical identity of the substance. The sodium ions and water molecules simply rearrange to mix together, but they can be separated again.

On the other hand, the other options are chemical changes:

• B. Iron rusts: This is a chemical change because new substances (rust) are formed and the process cannot be easily reversed.
• C. Iron is magnetised: This is a physical change, but it involves changes in the arrangement of electrons, which is a chemical property.
• D. Magnesium wire is burnt: This is a chemical change because burning (combustion) always results in new substances being formed (in this case, magnesium oxide and light).