(a) chemical (b) physical (c) physical (d) chemical
Work Step by Step
(a) chemical This is an example of a chemical change because bacteria act on the lactose in milk, turning it into lactic acid. (b) physical The change of phase from liquid to gas is a physical change because the water is still water, whether it is in the form of a liquid or a gas. (c) physical Creating copper wire from a copper bar is a physical change because the copper has not changed. (d) chemical This is an example of a chemical change because when an egg is being cooked, the proteins are chemically changed so that the proteins in the raw egg are not the same as those in the cooked egg.