Atoms and Molecules
Bonds and Octet Rules
VISUAL AIDSFunctional Groups
QUIZZESPractice Quiz I
Practice Quiz II
Practice Quiz III
Anything that can be weighed is matter. Rocks, water, wood, smoke, stars, air, and sand are all examples of different types of matter.
There are three different states in which matter can exist in the universe.
Scientists classify matter into two main categories: compounds and elements. A compound is matter that can be broken down into other types of matter, while an element is matter that cannot.
Liquid water is a compound because water can be separated into hydrogen gas and oxygen gas. But oxygen gas and hydrogen gas are elements because they cannot be broken down into other types of matter. Note, however, that oxygen gas (O2) and hydrogen gas (H2) are diatomic molecules (two atoms per molecule) and that, under certain conditions, they can be broken down into oxygen and hydrogen atoms, respectively.
A more general way in which scientists classify matter is substances and mixtures. A substance is any amount of matter, element or compound, of only one type. Pure water and pure table salt (sodium chloride) are substances because each consists of only one type of matter.
A mixture is any amount of matter that is a combination of more than one type of matter.
A solution of table salt in water is a mixture because it contains two different types of matter: water and table salt. The different types of matter in a mixture share the same space but retain their individual identities.
Properties of Matter
Matter can undergo physical and chemical changes. A physical change does not alter the identity of matter but a chemical change does. The following table provides examples of physical and chemical properties and changes, and an illustration follows.