Chapter 1
Q. 1.1
physical and Chemical Changes and Properties
Determine whether each change is physical or chemical. What kind of property (chemical or physical) is demonstrated in each case?
(a) the evaporation of rubbing alcohol
(b) the burning of lamp oil
(c) the bleaching of hair with hydrogen peroxide
(d) the formation of frost on a cold night
Step-by-Step
Verified Solution
(a) When rubbing alcohol evaporates, it changes from liquid to gas, but it remains alcohol—this is a physical change. The volatility (the ability to evaporate easily) of alcohol is therefore a physical property.
(b) Lamp oil burns because it reacts with oxygen in air to form carbon dioxide and water—this is a chemical change. The flammability of lamp oil is therefore a chemical property.
(c) Applying hydrogen peroxide to hair changes pigment molecules in hair that give it color—this is a chemical change. The susceptibility of hair to bleaching is therefore a chemical property.
(d) Frost forms on a cold night because water vapor in air changes its state to form solid ice—this is a physical change. The temperature at which water freezes is therefore a physical property.