David learns about chemistry from some household items and some uninvited guests.
Chemistry is the study of matter.
The basic building blocks of matter are the elements . Elements cannot be broken down into simpler matter. Whether in nature or in the laboratory, two or more elements combine chemically to form a compound . The combined form may have different properties from the original elements. For example, when the element oxygen, a gas, combines chemically in one way with the element hydrogen, also a gas, one compound that can be formed is water.