The document provides a review of various physics concepts including: - The metric unit for mass is grams. Matter with freely moving particles is a gas. The x-axis variable in data tables is usually represented by x. - Volume units include mL and cm3. Physical changes do not alter the identity of matter. - Density is a measure of mass within a volume. It is affected by how tightly packed particles are. Objects with the same volume but different masses have different densities.