Phases of Matter

Kinetic Theory All matter is made of atoms and molecules that act like tiny particles. These tiny particles are always in motion. The higher the temp., the faster the particles move. At the same temp., more massive (heavier) particles move slower than less massive (lighter) particles.

SOLIDS Definite shape? YES Definite volume? YES Molecules in a solid are tightly packed and constantly vibrating.

LIQUIDS Definite shape? NO Definite volume? YES Some liquids flow more easily than others. The resistance of a liquid to flow is called viscosity. –Honey has a high viscosity compared to water.

GASES Definite shape? NO Definite volume? NO The particles in a gas are spread very far apart, but can be compressed by pumping them into a restricted volume.

Phase Changes Changes in phase are examples of physical changes. Melting: solid  liquid Freezing: liquid  solid Vaporization: liquid  gas Condensation: gas  liquid Sublimation: solid  gas

Changes of State GAS SOLID Deposition Sublimation Vaporization Condensation Melting Freezing LIQUID Melting

ENERGY is the ability to change or move matter. Energy is ABSORBED when substances melt or evaporate. –NOTE: our bodies cool down when our sweat evaporates. Energy is RELEASED when substances freeze or condense.

Melting The change of state from solid to liquid. Energy (heat) is absorbed by the substance that is melting.

Freezing The change of state from liquid to solid. Opposite of melting. Energy (heat) is released by the substance undergoing freezing.

Evaporation The change of state at the surface of a liquid as it passes to a vapor. This results from the random motion of molecules that occasionally escape from the liquid surface. –Energy (heat) is absorbed by the liquid (Cooling of the liquid results) –Can happen at any temperature

Condensation The change of state from gas to liquid. The opposite of evaporation. –Energy (heat) is released by the liquid (Warming of the liquid results)

Boiling Change from state from a liquid to a gas. Occurs throughout the liquid. –boiling point/temperature is determined by pressure –Energy (heat) is absorbed by the liquid.

*Boiling & freezing points depend on the pressure.

Water at normal pressure (1 atm): For water at normal (every day) pressures: Melting/freezing point: Condensing/boiling point: 0 o C (32 o F) 100 o C (212 o F) Label the points & temperatures on your graph.

Change the pressure  Change the Boiling Point

Phase Diagrams a phase diagram shows the equilibria pressure- temperature relationship among the different phases of a given substance

AB =AC = AD = C WATER Carbon Dioxide

AB =AC = AD = C melting curve

AB =AC = AD = C melting curve sublimation curve

AB =AC = AD = C melting curve sublimation curve vapor pressure curve

triple point = Point ______ The point at which all 3 phases of a substance (solid, liquid, gas) can coexist at equilibrium. critical point = Point ______ The combination of critical temperature and critical pressure. A C D critical temp = temp. above which a gas cannot be liquefied. (H 2 O=374ºC) critical pressure = press. required to liquefy a gas at its critical temperature. (H 2 O=218 atm)

Conditions for H 2 O on other planets…