sceince exam

Matter

Anything that has mass and takes up space.

Pure substance

Contains only one type of particle; can be an element or a compound.

Element

A substance that contains only one type of atom (e.g., Au, O₂, N₂).

Compound

A substance formed when two or more different elements are chemically bonded (e.g., H₂O, CO₂, NaCl).

Mixture

Contains two or more substances that are physically mixed together and can be separated physically (e.g., air, salt water).

Physical change

Does not create a new substance (e.g., melting, freezing).

Chemical change

Creates a new substance (e.g., burning, rusting).

Density

The amount of mass in a given volume, calculated using D = m/V.

Atom

The basic unit of a chemical element, made of protons, neutrons, and electrons.

Atomic number

Equals the number of protons in an atom.

Mass number

The total number of protons and neutrons in an atom.

Neutrons

Neutral particles in an atom; calculated by subtracting atomic number from mass number.

Rutherford-Bohr diagram

A diagram that shows electrons arranged in shells.

Valence electrons

Electrons in the outer shell that determine bonding.

Ion

An atom that gains or loses electrons.

Ionic bond

Forms when electrons are transferred from a metal to a non-metal.

Ionic compound

Named using the metal name plus non-metal ending in '-ide' (e.g., sodium chloride).

Molecular (covalent) compound

Forms between two non-metals and shares electrons.

Electricity

The movement of electrons.

Like charges

Repel each other.

Opposite charges

Attract each other.

Conductor

Material that allows electricity to flow easily (e.g., copper, aluminum).

Insulator

Material that resists the flow of electricity (e.g., rubber, plastic).

Ammeter

Measures current and is connected in series.

Voltmeter

Measures voltage and is connected in parallel.

Ohm's Law

States that V = IR; relationship between voltage, current, and resistance.

Power

How fast energy is used, calculated using P = VI.

Efficiency

Measures how much energy becomes useful, calculated as Useful Output ÷ Total Input × 100%.

Ecosystem

All the living and non-living things interacting in an environment.

Biotic factors

Living or once-living