Chemistry Class 1.2: Classification of Matter

Study Notes

Matter occupies space and has mass; examples include gold, iridium, peanuts, people, and smoke.
Energy, light, and sound, along with ideas and emotions, are not considered matter.
Mass represents the quantity of matter in an object and remains constant regardless of location; weight is affected by gravitational force.
An astronaut's mass (95 kg) results in a weight of approximately 210 lb on Earth and about 35 lb on the Moon.
Weight and mass are often used interchangeably in laboratories; 2.2 lb (weight) equals 1.0 kg (mass) under Earth's gravity.
Matter exists in three states: solids (fixed shape and volume), liquids (fixed volume but conforming shape), and gases (no fixed shape or volume).
Physical changes, such as water turning to steam or back, do not alter the chemical composition of substances.

A pure chemical substance has a fixed composition and distinctive properties, such as oxygen being a colorless, odorless gas at 25°C.
Most materials are mixtures, consisting of two or more pure substances retaining their individual identities.
Homogeneous mixtures are uniform throughout, e.g., air and tap water; these are also known as solutions, with variable compositions based on source or location.
Solid solutions (alloys) also exist, such as dental amalgam with 50% mercury and various metals.
Heterogeneous mixtures are not uniform, displaying visible differences; examples include chocolate chip cookie dough and blue cheese.
Homogeneous appearances can be misleading; substances like milk appear uniform but have distinct components when examined microscopically.