Solid, liquid, and gas.

Particles are tightly packed, arranged in a fixed pattern, and only vibrate in place. Solids have a definite shape and volume.

Particles are close together but can move past each other. Liquids have a definite volume but take the shape of their container.

Particles are far apart, move freely and rapidly, and gases have neither a fixed shape nor volume.

Melting.

Freezing or solidification.

Evaporation or boiling.

Condensation.

The direct change from solid to gas (e.g., dry ice).

The smallest unit of an element that retains its chemical properties.

A substance made of only one type of atom.

A substance made of two or more different elements chemically combined in fixed proportions.

Using chemical symbols (e.g., H for hydrogen, O for oxygen).

Two or more atoms bonded together (e.g., H₂O, O₂).

By increasing atomic number, in periods (rows) and groups (columns) with similar properties.

The amount of substance containing the same number of particles as 12g of carbon-12.

6.022×10²³ particles (atoms, molecules, ions).

Moles = mass (g) / molar mass (g/mol).

Sum of atomic masses of all atoms in a molecule.

A reaction that releases heat to the surroundings (e.g., combustion, respiration).

A reaction that absorbs heat from the surroundings (e.g., photosynthesis, thermal decomposition).

By observing temperature change: increase = exothermic, decrease = endothermic.

Temperature, concentration, surface area, catalysts, and pressure.

Higher temperature increases particle energy, increasing collision frequency and energy.

Higher concentration means more particles in a given volume, leading to more frequent collisions.

A substance that speeds up a reaction without being consumed, by providing an alternative pathway with lower activation energy.

A substance that produces H⁺ ions in solution (e.g., hydrochloric acid).

A substance that produces OH⁻ ions in solution (e.g., sodium hydroxide).

An acid reacts with a base to produce salt and water.

Using litmus paper: acids turn blue litmus red; bases turn red litmus blue.

An ionic compound formed from the neutralization of an acid with a base.

Sodium chloride (NaCl), calcium carbonate (CaCO₃), copper sulfate (CuSO₄).

Dmitri Mendeleev.

Increasing atomic number.

Vertical columns; elements in the same group have similar chemical properties.

Horizontal rows; elements in the same period have the same number of electron shells.

Lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr).

Good conductors of heat and electricity, malleable, ductile, shiny, high melting points.

Iron, copper, aluminum, zinc, gold, silver.

The rusting of iron when it reacts with oxygen and water.

By electrolysis (for reactive metals) or reduction with carbon (for less reactive metals).

To separate insoluble solids from liquids.

To separate mixtures based on different boiling points.

To separate and identify components in a mixture.

To obtain pure solid crystals from a solution.

Using chemical tests, flame tests, pH tests, and spectroscopy.

Heating a substance and observing the color of the flame to identify metal ions.

Using test tubes and reagents (e.g., limewater for CO₂, litmus paper for acids).