Is it true that a physical property of a substance can change if no chemical change occurs?
A chemical change takes place when the chemical composition of a material is changed. For example, burning of fossil fuels is a chemical change as we end up with carbon dioxide and water vapor (along with heat), while we started out with fossil fuel (an organic compound). A physical change, on the other hand, is a change that does not require a change in chemical composition of the material. An example of physical change is melting of ice, in which solid ice converts to liquid water.
It is not necessary for a change in physical property to be accompanied by chemical change. An example is the density of water and water vapor. When water changes from ice to water and to the water vapor phase, no change in chemical composition takes place, yet the density of the water in each of these phases is different. The specific gravity is also different.
Thus, a change in physical property is possible without change in chemical composition.
Hope this helps.