science notes

Solid

Has a definite shape and fixed volume; particles are closely packed in a rigid structure.

Liquid

Has an indefinite shape and fixed volume; particles slide past one another with moderate intermolecular forces.

Gas

Has an indefinite shape and volume; particles are widely separated and move rapidly.

Melting

Phase change from solid to liquid, endothermic process that absorbs heat.

Freezing

Phase change from liquid to solid, exothermic process that releases heat.

Vaporisation

Phase change from liquid to gas, an endothermic process that absorbs heat.

Boiling

Bulk process occurring at a defined boiling point.

Condensation

Phase change from gas to liquid, an exothermic process that releases heat.

Sublimation

Direct change from solid to gas without going through the liquid state.

Deposition

Direct change from gas to solid without entering the liquid state.

Physical Properties

Characteristics observed without altering the chemical identity of a substance.

Intensive Properties

Properties independent of the amount of substance (e.g., density, boiling point).

Extensive Properties

Properties proportional to the size or mass of a sample (e.g., mass, volume).

Chemical Properties

Characteristics that describe the ability of a substance to form new chemical substances.

Density ($\rho$)

Defined as mass per unit volume ($\rho = \frac{m}{V}$) and is an intensive property.

Atom

Basic unit of a chemical element, consisting of protons, neutrons, and electrons.

Proton ($p^+$)

A positively charged subatomic particle found in the nucleus.

Neutron ($n^0$)

A neutral subatomic particle found in the nucleus.

Electron ($e^-$)

A negatively charged subatomic particle found in electron shells surrounding the nucleus.

Atomic Number ($Z$)

Number of protons in an atom, defining the element.

Mass Number ($A$)

Sum of protons and neutrons in the nucleus, $A = Z + N$.

Neutron Number ($N$)

Calculated as $N = A - Z$, representing the number of neutrons.

Isotopes

Atoms of the same element with the same atomic number but different mass numbers.

Relative Atomic Mass ($A_r$)

Calculated using isotopic mass and percentage abundance.

Scientific Notation

Number expressed in the form $N \times 10^n$ where $1 \leq |N| < 10$.

Significant Figures

Digits in a number that carry meaning contributing to its precision.

Mass Rearrangement Formula

Formula to solve for mass: $m = \rho \times V$.

Volume Rearrangement Formula

Formula to solve for volume: $V = \frac{m}{\rho}$.

Maximum Electron Shell Capacity Formula

Calculated as $\text{Maximum Capacity} = 2n^2$.

Cation Formation

Process by which a neutral atom loses electrons to form a positively charged ion.

Anion Formation

Process by which a neutral atom gains electrons to form a negatively charged ion.