Year 9 Chemistry Revision Flashcards

A complete list of vocabulary flashcards covering key topics from the Year 9 Chemistry Revision Checklist, including atomic structure, the periodic table, chemical equations, conservation of mass, reaction rates, collision theory, ions, and practical experimental variables.

Atom

The basic unit of a chemical element, consisting of a central nucleus surrounded by electrons.

Subatomic Particle

A particle smaller than an atom, specifically a proton, neutron, or electron.

Nucleus

The small, dense central core of an atom containing protons and neutrons.

Electron Shells

The regions or energy levels surrounding an atomic nucleus where electrons are located.

Proton

A subatomic particle located in the nucleus with a positive charge.

Neutron

A subatomic particle located in the nucleus with no charge (neutral).

Electron

A subatomic particle located in the electron shells with a negative charge.

Atomic Number

The number of protons in an atom, which determines the element's position on the Periodic Table.

Mass Number

The total number of protons and neutrons in an atom's nucleus.

Group

A vertical column on the Periodic Table containing elements with the same number of valence electrons.

Period

A horizontal row on the Periodic Table.

Valence Shell

The outermost electron shell of an atom.

Electron Configuration

The distribution or arrangement of electrons in the main electron shells of an atom.

Element

A pure substance composed of only one type of atom.

Compound

A substance formed when two or more different elements are chemically combined.

Molecule

A particle composed of two or more atoms chemically bonded together, which can be of the same or different elements.

Mixtures

Combinations of two or more substances that are physically combined rather than chemically bonded.

Chemical Reaction

A process involving the breaking and reforming of chemical bonds to convert reactants into products.

Reactants

The starting substances written on the left side of a chemical equation.

Products

The substances formed during a chemical reaction, written on the right side of an equation.

State Symbols

Symbols indicating physical state in chemical equations: $(s)$ for solid, $(l)$ for liquid, $(g)$ for gas, and $(aq)$ for aqueous solution.

Subscript Numbers

Small numbers written lower and to the right of chemical symbols in a formula (e.g., the 2 and 4 in $H_2SO_4$) indicating the number of atoms of that element.

Coefficients

Numbers placed in front of chemical formulas (e.g., the 2 in $2HCl$) to balance chemical equations.

Law of Conservation of Mass

The principle stating that mass is neither created nor destroyed during a chemical reaction.

Collision Theory

A theory stating that chemical reactions occur when reactant particles collide with sufficient energy and correct orientation.

Rate of Reaction

A measure of how fast reactants are converted into products during a chemical reaction.

Catalyst

A substance that increases the rate of a chemical reaction without being consumed in the process.

Noble Gases

Elements that do not form ions because they already possess a full outer electron shell.

Cation

A positively charged ion formed when an atom loses electrons.

Anion

A negatively charged ion formed when an atom gains electrons.

Independent Variable

The variable in an experiment that is deliberately changed by the experimenter.

Dependent Variable

The variable in an experiment that is measured to test the effect of the independent variable.

Controlled Variables

The variables in an experiment that are kept constant to ensure a fair test.