Year 8 Chemistry and Physical Sciences Review

Comprehensive vocabulary flashcards covering experimental variables, density, physical properties of matter, atomic structure, and chemical reactions.

Independent Variable

The variable in an experiment that you are deliberately changing.

Dependent Variable

The variable in an experiment that is being measured.

Controlled Variable

A variable that must stay the same throughout an experiment to maintain valid results.

Fair Test

An experimental setup having exactly one independent variable while all other variables are controlled.

Control Test

An external group separate from the rest of the experiment where the factor being tested cannot influence the results, confirming whether the independent variable is responsible for changes.

Density

A measure of how tightly packed the mass of a material is within a given volume, calculated as $\text{density} = \frac{\text{mass}}{\text{volume}}$.

Displacement Method

A technique used to determine the volume of an irregular object by placing it into a known volume of water in a beaker and calculating the increase in volume.

Malleable

A physical property of metals describing the ability to be shaped or hammered without shattering.

Ductile

A physical property of metals describing the ability to be drawn or stretched into wire.

Brittle

A characteristic property of non-metals describing a tendency to shatter rather than deform under stress.

Metalloids

Elements located along the staircase line on the periodic table that exhibit properties of both metals and non-metals.

Chemical Reaction

A process that permanently changes one or more substances into one or more new substances.

Reactants

The original substances that take part in and are changed during a chemical reaction.

Products

The new substances that are formed as a result of a chemical reaction.

Precipitate

An insoluble solid that forms when two liquid solutions are mixed together.

Aqueous ($(aq)$)

A state describing atoms or molecules dissolved and spread out in water; all acids are classified as aqueous.

Physical Change

A change in state, shape, or size in which no new substance is formed, and which is usually reversible.

Melting Point

The specific temperature at which a solid turns into a liquid.

Boiling Point

The specific temperature at which a liquid turns into a gas.

Viscosity

A fluid's internal resistance to flowing, where high viscosity represents thick substances and low viscosity represents free-flowing liquids.

Electrical Conductivity

A property describing how easily an electrical current moves through a material.

Diffusion

The net movement of particles from a region of high concentration to a region of low concentration.

Hardness

A material's structural resistance to surface deformation, scratching, or denting.

Atom

The smallest unit of matter that retains the chemical properties of an element.

Element

A pure substance composed of only one kind of atom.

Molecule

A particle formed when two or more atoms are chemically bonded together.

Compound

A substance composed of two or more different elements chemically bonded together.

Circumference

The distance measured around the centre of an object, such as an inflated balloon.

Thermal Expansion of Gases

The increase in volume of a gas as temperature increases, caused by gas particles gaining heat energy, moving faster, crashing, and spreading farther apart.

Sublimation

The change of state in which a solid turns directly into a gas without passing through the liquid phase.

Atomic Number

The number of protons found in the nucleus of an atom of an element.

Mass Number

The total number of protons and neutrons contained in the nucleus of an atom.

Electron

A negatively charged subatomic particle located in energy shells with almost no mass.

Noble Gases

The elements situated in Group $18$ of the periodic table, including helium and argon.

Exothermic Reaction

A chemical reaction that releases energy, causing the temperature of the surroundings to increase.