MLS Chemistry Chapter 2: Matter and Energy

Study Notes

Matter is defined as anything that has mass and occupies space.
Traditionally categorized into three states: solid, liquid, gas, with two additional states identified: plasma and Bose-Einstein Condensate.
Pure Substances: Uniform chemical composition with distinct properties.
- Elements: Cannot be separated into simpler substances (e.g., H, He, O).
- Compounds: Composed of two or more elements in fixed proportions, separable by chemical means (e.g., H₂O, NaCl).
Mixtures: Comprises two or more pure substances retaining their identities and separable by physical methods.
- Homogeneous Mixtures: Uniform composition (e.g., solutions like vinegar).
- Heterogeneous Mixtures: Non-uniform composition (e.g., colloids like milk, suspensions like muddy water).

Solid: Fixed shape and volume; high density; incompressible; slight thermal expansion.
Liquid: Takes the shape of its container; definite volume; medium density; can be compressed slightly.
Gas: No fixed shape or volume; low density; highly compressible; significant thermal expansion.
Plasma: Composed of ions and electrons; no definite shape/volume; typically found in high-energy environments.
Bose-Einstein Condensate: Exists at near absolute zero; particles are highly correlated, showing quantum behavior on a macroscopic scale.

Physical Properties: Observable or measurable without altering the substance (e.g., color, hardness, melting/boiling point).
Chemical Properties: Ability of a substance to undergo chemical changes (e.g., flammability, reactivity).
- Intensive Properties: Independent of amount (e.g., temperature, density).
- Extensive Properties: Dependent on the amount (e.g., mass, volume).
Phase Changes:
- Melting: Solid to Liquid
- Freezing: Liquid to Solid
- Evaporation: Liquid to Gas
- Condensation: Gas to Liquid
- Sublimation: Solid to Gas
- Deposition: Gas to Solid
- Ionization: Gas to Plasma
- Deionization: Plasma to Gas
- Cooling to near absolute zero: Gas to Bose-Einstein Condensate

Law of Conservation of Matter: Matter is not created or destroyed; mass of reactants equals mass of products in a closed system.
Law of Definite Composition: A compound always contains the same proportion of elements by mass (e.g., water is 11% hydrogen, 89% oxygen).
Law of Multiple Proportions: When two elements form multiple compounds, the mass ratios of the second element are small whole numbers (e.g., CO and CO₂ have a 2:1 mass ratio of oxygen).