States of Matter Kinetic Molecular Theory Explanation for

States of Matter

Kinetic Molecular Theory Explanation for atoms/molecules’ behavior within a state of matter. Views atoms/molecules within matter in constant motion. Explains properties associated with solids, liquids, and gases

3 Phases of Matter Solid Liquid Gas

How do particles move in a solid?

Solids Have a definite shape/structure, high density (most), cannot be compressed Very little particle movement—fixed position “vibrate” in a fixed position Intermolecular forces strongest in this state of matter Crystals– particle arrangement in a repeating, geometric pattern Amorphous solid– soild with random arrangement of particles

How do particles move in a liquid?

Liquids Limited structure to particles, definite volume Diffusion is possible (liquids can mix together), more compressible than solids Movement is less restricted, particles can move around and collide with each other Less intermolecular force attraction among these particles Conform to a container’s shape, exhibits “flow”—fluid Exhibit surface tension (force allowing the liquid to adhere to a surface)

Gases No structure—no definite volume or shape Movement is not restricted Fluid—gas particles can “flow” among each other Particles are always in motion Expansion occurs but capable of being compressed Least dense state Diffusion is possible (gases can mix together)

Phase Changes Boiling/Evaporation—a liquid is changing to a gas Condensation—a gas is changing into a liquid Sublimation—a solid converts directly into a gas, skips the liquid phase Melting and freezing ? ?

Phase Diagrams Graph plot of temperature vs. pressure Indicates what physical conditions MUST exist for each phase of a substance Specific for each substance

Phase Diagram of Water

Equilibrium– balanced state, 2 opposite changes are happening at equal rates Critical Point– point on the diagram where substance cannot be converted back into a liquid from a gaseous state Contains both critical temperature ( > than, cannot go back to liquid) and critical pressure (lowest pressure for liquid state at critical temperature) Triple Point– point on the diagram where a substance exists in equilibrium between all three phases (solid, liquid, gas)

Melting Point– a substance goes from a solid to a liquid at this temperature Boiling Point– liquid vaporizes, the external atmosphere pressure = vapor pressure of the liquid