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? 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? 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 SOLID GAS LIQUID Melting Vaporization Condensation Deposition Sublimation Vaporization Condensation Melting Freezing LIQUID

ENERGY TRANSFERS!!! 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 Evaporation: the process in which molecules escape from the surface of a liquid; can happen at any temperature, but occurs more rapidly as temperature increases.

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 A rapid state of evaporation that takes place within the liquid as well as at it’s surface. Like evaporation, cooling of the liquid results. Boiling point: the temperature at which the vapor pressure of the liquid equals the ambient (surrounding) pressure. ***the normal boiling pt = the temp at which a liquid’s vapor pressure = 760 mm Hg or 1 atm

Vaporization (evaporation and boiling) vapor pressure: the pressure exerted by the vapor of the liquid on its surface at equilibrium in a closed container; increases as temperature increases ***liquids with high boiling points have low vapor pressures and relatively strong intermolecular attractions.

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)

Sublimation

Deposition

Phase Change Graph *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 oC (32oF) 100 oC (212oF) 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

WATER Carbon Dioxide C AD = AB = AC =

C melting curve AD = AB = AC =

C melting curve sublimation curve AD = AB = AC =

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

A D triple point = Point ______ C A triple point = Point ______ The point at which all 3 phases of a substance (solid, liquid, gas) can coexist at equilibrium. D critical point = Point ______ The combination of critical temperature and critical pressure. critical temp = temp. above which a gas cannot be liquefied. (H2O=374ºC) critical pressure = press. required to liquefy a gas at its critical temperature. (H2O=218 atm)

Conditions for H2O on other planets…