Matter, Properties, and Chemical Reactions: Key Concepts for Chemistry

Matter

Anything that has mass and takes up space.

Mass

Measure of how much matter is in an object.

Volume

Amount of space an object takes up.

Solid

State of matter with tightly packed particles, definite shape, definite volume.

Liquid

State of matter with close but movable particles, definite volume, variable shape.

Gas

State of matter with far-apart particles, no definite shape or volume.

Definite shape

Property of solids.

Definite volume

Property of solids and liquids.

(s)

Symbol for solid in chemical notation.

(l)

Symbol for liquid in chemical notation.

(g)

Symbol for gas in chemical notation.

(aq)

Symbol for aqueous solution in chemical notation.

Example of solid

Ice.

Example of liquid

Water.

Example of gas

Oxygen.

Physical property

Observed without changing composition (e.g., color, density, melting point).

Chemical property

Observed only when composition changes (e.g., flammability, reactivity).

Intensive property

Does not depend on amount of matter (e.g., density, melting point).

Extensive property

Depends on amount of matter (e.g., mass, volume).

Density

Intensive property that stays the same regardless of sample size.

Melting point

Intensive property; same no matter the amount.

Physical properties of water

Colorless, boiling point 100 °C.

Chemical properties of water

Reacts with sodium, decomposes into H₂ + O₂.

Flammability

Chemical property because composition changes when burning.

Element

Substance with one type of atom (O₂, Au).

Compound

Substance made of two or more elements chemically combined (H₂O, NaCl).

Mixture

Two or more substances physically combined.

Homogeneous mixture

Uniform throughout (air, salt water, steel alloy).

Heterogeneous mixture

Not uniform throughout (salad, cookie).

Tap water

Homogeneous mixture with dissolved minerals and additives.

Difference between compound & mixture

Compounds are chemically bonded; mixtures are physically blended.

Filtration

Separates solids from liquids based on particle size.

Distillation

Separates substances by differences in boiling points.

Centrifuge

Separates substances by density.

Separatory funnel

Separates immiscible liquids by density (layers).

Chromatography

Separates substances by solubility and movement on paper.

Example: Sand + salt water

Filtration for sand, then evaporation for salt.

Physical change

Change without new substance; composition stays the same (melting ice, tearing paper).

Chemical change

Change that forms a new substance (burning wood, rusting iron).

Signs of chemical change

Gas produced, color change, precipitate, energy/odor change.

Dissolving sugar

Physical change.

Melting cheese

Physical change.

Burning wood

Chemical change.

Baking a cake

Chemical change.

Law of Conservation of Mass

Matter cannot be created or destroyed in a chemical reaction.

Coefficients in equations

Show the number of molecules.

Subscripts in equations

Show the number of atoms in a molecule (never change them).

Balanced equation: H₂ + O₂ → H₂O

2H₂ + O₂ → 2H₂O.

Balanced equation: KClO₃ → KCl + O₂

2KClO₃ → 2KCl + 3O₂.

Balanced equation: CH₄ + O₂ → CO₂ + H₂O

CH₄ + 2O₂ → CO₂ + 2H₂O.