Question

which of these is an example of a physical change?
sugar dissolving in warm water
iron rusting in the presence of moist air
wood burning in the presence of oxygen
baking soda reacting with acid to form a gas

Explanation:

A physical change is a change in which the substance's chemical composition remains the same. When sugar dissolves in warm water, it only changes its state from solid to dissolved in water without forming a new chemical substance. Iron rusting, wood - burning, and baking soda reacting with acid are all chemical changes as new substances are formed.

Answer:

sugar dissolving in warm water