Ch. 2 Key Terms Earth Science

Atom

The smallest neutral particle of an element that retains the characteristics of that element, composed of a positive nucleus containing protons and usually neutrons, surrounded by negatively charged electrons.

Boiling

The change of state from liquid to a gas at the boiling point, occurring when the pressure in the liquid exceeds the atmospheric pressure.

Chemical change

The change of one pure substance to another by the rearrangement of atoms in a chemical reaction, typically recognized by changes in color, energy, gas formation, or solid formation.

Compound

A pure substance formed by chemically combining two or more elements.

Condensation

The change in state from gas to a liquid by removing energy, occurring at the dew point and opposite of vaporization.

Deposition

The change in state from a gas directly to a solid caused by removing energy, opposite of sublimation.

Element

A pure substance made of only one kind of atom.

Energy

The ability to do work; exists in various forms and can transfer between objects or change form.

Evaporation

The change of state from liquid to a gas below the boiling point but above the freezing point, occurring when surface particles gain sufficient energy to escape the liquid.

First law of thermodynamics

Scientific law stating that matter and energy cannot be created or destroyed, only transferred or transformed, also known as the law of conservation of matter and energy.

Force

A push or pull on an object.

Freezing

The change of state from liquid to a solid caused by removing energy, opposite of melting.

Gas

A fluid state of matter with fast-moving particles that are far apart; has changeable shape and volume.

Gravity

The attraction force between any two objects based on their masses, weakening rapidly as the objects move apart.

Ion

A charged atom or group of atoms due to a charge imbalance, from an unequal number of protons and electrons.

Liquid

A fluid state of matter where particles can move freely but are close together, having unchanging volume but changeable shape.

Mass

The measure of the amount of matter in an object.

Matter

Anything that has mass and takes up space; a physical substance.

Melting

The change of state from solid to a liquid at the melting point caused by adding energy, opposite of freezing.

Mixture

A physical combination of two or more substances that can be separated by physical means.

Molecule

Two or more chemically bonded atoms, which can be made of one element or a combination of elements.

Nuclear change

A change of one element into another by changes occurring in the atom's nucleus, occurring through emission or absorption of rays/particles or during fusion.

Physical change

A change in matter that does not alter its chemical identity, including changes of state, shape, polishing, or dissolving.

Plasma

A fluid state of matter made of extremely high-temperature ionized particles, having both changeable shape and volume.

Pure substance

A material made of only one kind of element or compound; not a mixture.

Solid

A rigid state of matter with particles aligned in a fixed arrangement, having unchanging shape and volume.

State of matter

The physical form of matter described by its characteristics, depending on temperature; includes solid, liquid, gas, or plasma.

Sublimation

The change of state from a solid directly to a gas caused by adding energy; opposite of deposition.

Temperature

The hotness or coldness of a substance, measured in degrees, representing the average kinetic energy of its particles.

Vaporization

The change of state from a liquid to a gas caused by adding energy; opposite of condensation.

Volume

The amount of space that an object occupies.

Weight

The force of gravitational attraction between an object's mass and its planet.

Work

Work is