Properties of Solids, Liquids, and Gases: Particle Theory, Density, and Changes of State

Vocabulary practice flashcards covering states of matter, particle theory explanations, physical versus chemical changes, density, gas pressure, and state change energetics based on the science workbook unit.

Solid

A state of matter that has a definite shape, cannot be compressed, and cannot diffuse because its particles are packed closest together, have the least energy, and vibrate in fixed positions.

Liquid

A state of matter that takes the shape of the bottom of its container, cannot be compressed, and diffuses slowly, having particles that are close together but free to move past one another.

Gas

A state of matter that takes the shape of its container and completely fills it, compresses easily, and diffuses quickly because its particles have the most energy, move fastest, and are the greatest distance apart.

Physical Change

A change in which no new substances are formed and which can easily be reversed, such as changes of state like ice melting or water boiling.

Chemical Change

A change in which new substances are formed and which is not easily reversed, such as wax burning to form carbon dioxide and water, or hydrogen reacting with oxygen to produce water.

Conservation of Mass (in State Changes)

The principle that mass remains unchanged during physical changes of state; for example, converting $100\,\text{g}$ of ice produces exactly $100\,\text{g}$ of liquid water and subsequently $100\,\text{g}$ of steam.

Mass

The amount of matter contained in an object.

Volume

The amount of space that an object occupies.

Density

How much mass is contained in a definite volume, determined by the mass of the individual particles and how closely packed together they are in a given space.

Relative Density (Flotation)

The relationship determining whether an object floats or sinks in a liquid; a substance floats if its density is less than the liquid (such as cork in water) and sinks if its density is greater (such as lead in water).

Gas Pressure

The outward force created inside a container by gas particles continuously colliding with each other and colliding with the walls of the container.

Melting

The physical change from a solid to a liquid occurring when a solid is heated; particles absorb energy, vibrate more violently, expand, and eventually break away from their fixed positions.

Freezing

The physical change of state from a liquid to a solid occurring when heat energy is removed; particles lose energy, move more slowly, vibrate less, and form rigid bonds.

Evaporation

The change of a liquid into a gas that can occur at any temperature at the liquid's surface, with its rate increasing as the temperature rises because particles move faster.

Boiling

The rapid change of state from liquid to gas occurring at a specific boiling point, where particles gain sufficient energy to form bubbles of gas throughout the liquid that rise to the surface and break away.

Condensation

The physical change of state from a gas to a liquid occurring when gas particles cool down, lose energy, move more slowly, and begin forming attractive bonds.

Processes that Require Energy

Changes of state that absorb thermal energy to increase particle movement and break intermolecular bonds, specifically melting, boiling, and evaporation.

Processes that Give Out Energy

Changes of state that release thermal energy to the surroundings as particles slow down and form bonds, specifically condensation and freezing.

Compressibility

The ability of a substance to be squeezed into a smaller volume; gases compress easily due to large spaces between particles, whereas solids and liquids cannot be compressed because their particles are already closely packed.

Diffusion

The spreading of particles through a substance from an area of higher concentration; gases diffuse rapidly because particles move quickly with large spaces between them, liquids diffuse slowly, and solids cannot diffuse.