Natural Science CLEP Prep Practice Exam

An example of a physical change is a change in the physical properties of a substance without altering its chemical composition. Burning a log (choice A) involves a chemical reaction, as the log is being transformed into ash. Changing the temperature of a river (choice C) is a form of energy transfer, but does not change the substance itself. Evaporating a drop of water (choice D) is also a form of energy transfer. Therefore, melting a bar of metal (choice B) is the best example of a physical change, as the solid metal is simply changing into liquid form without any alteration of its chemical composition.