Science notes - Sem 1 2025

Chemical change

A process that makes a new substance by rearranging atoms.

Physical change

A change that affects the appearance of a substance but not its chemical makeup.

Atom

The smallest unit of matter, made up of tiny particles.

Element

A substance made of only one type of atom.

Protons

Positively charged particles found in the center of an atom.

Neutrons

Neutral particles found in the nucleus of an atom.

Electrons

Negatively charged particles that move around the nucleus of an atom.

Synthesis

A reaction where simpler substances combine to make a more complex one.

Decomposition

A reaction that breaks down a complex substance into simpler parts.

Reactants

The starting materials in a chemical reaction.

Products

The new substances formed in a chemical reaction.

Diatomic

Molecules made of two atoms of the same element.

Particle collision

When two or more particles interact, often causing a reaction.

Independent variable

The part of the experiment that is changed.

Dependent variable

The part of the experiment that is measured.

Control variable

The part of the experiment that stays the same to keep it fair.

Rate of reaction

How fast reactants turn into products in a reaction.

Collision theory

A theory that explains how reaction rates depend on particle collisions.

Oxygen test

A burnt splint is used to check if oxygen is present.

Hydrogen test

A pop sound indicates the presence of hydrogen.

Carbon dioxide test

Limewater is used to check for carbon dioxide.