Matter: States & Changes Summary & Study Notes

🧊 Matter Basics

Matter is anything that has mass and occupies space. It includes solids, liquids, gases, and plasma. An extensive property (depends on amount) includes mass and volume; an intensive property (does not depend on amount) includes density, color, and boiling point.

Mass is the amount of matter in an object, typically measured in kilograms (kg). Volume is the space that matter occupies, with common units such as liters (L) or cubic meters (m^3).

Density is defined as $\rho = \frac{m}{V}$ and has units of $kg/m^3$; it tells how tightly matter is packed.

🧪 Kinetic Theory & States of Matter

The Kinetic Theory describes matter in terms of energy and motion of particles. In a solid, particles vibrate in place and have a definite shape and volume. In a liquid, particles slide past each other and have a definite volume but take the shape of their container. In a gas, particles move freely and fill the space available to them.

Phase Changes

Phase changes are physical changes where matter changes state but not chemical identity. Common phase changes include:

• Melting (solid to liquid): energy is absorbed.
• Freezing (liquid to solid): energy is released.
• Vaporization (liquid to gas): energy is absorbed. This includes evaporation and boiling.
• Condensation (gas to liquid): energy is released.
• Sublimation (solid to gas): energy is absorbed.
• Deposition (gas to solid): energy is released.

$$q = m L$$

During phase changes, the temperature of the substance remains constant while energy is used to change its state; $L$ is latent heat.

Physical vs Chemical Changes

A physical change affects appearance or state but not the identity of the substance. Examples include crushing, cutting, and phase changes like melting. A chemical change forms new substances with different properties. Evidence includes color change, odor change, precipitate formation, gas production, or heat/light release.

Matter Composition

Matter is made of atoms and molecules.

• The atom is the smallest unit of an element and the basic unit of chemical behavior.
• The molecule is two or more atoms bonded together.
• An element is a pure substance consisting of one type of atom.
• A compound is a substance formed when two or more elements combine chemically in fixed ratios.
• A mixture contains two or more substances that are physically blended and can be separated by physical means.

Mixtures vs Pure Substances

A mixture has no fixed composition and can be separated into its components by physical means. A pure substance has a fixed composition and includes elements and compounds.

Properties & Identification

Physical properties (color, density, hardness, melting/boiling points) describe materials without changing composition. Chemical properties describe how a substance reacts with other substances (flammability, reactivity).

Evidence of a chemical change includes a new substance with different properties, energy release or absorption, gas production, or precipitate formation.

Key Terms

• Matter — anything that has mass and occupies space.
• Mass — the amount of matter in an object; typically measured in kilograms.
• Volume — the space that matter occupies; units include liters or cubic meters.
• Density — mass per unit volume; an intensive property.
• Atom — the smallest unit of an element.
• Molecule — a group of two or more atoms bonded together.
• Element — a substance of a single type of atom.
• Compound — a substance formed from two or more elements chemically bonded.
• Mixture — a combination of substances not chemically bonded.
• Pure substance — a substance with fixed composition.
• Physical property — can be observed without changing identity.
• Chemical property — describes how a substance may react chemically.
• Physical change — changes in form or state without changing identity.
• Chemical change — results in new substances with different properties.
• Phase change — solid-liquid-gas transitions.