Changes in States of Matter

Changes in States of Matter Change in State Process of Change Melting Freezing Boiling (Vaporization) Condensation Sublimation Deposition solid to liquid liquid to solid liquid to gas gas to liquid Solid to gas Gas to solid

Liquid to Gas Phase Change Vaporization - the change from a liquid to a gas below its boiling point. Evaporation - vaporization of an uncontained liquid ( no lid on the bottle ).

Evaporation Molecules at the surface break away and become gas. Only those with enough KE escape Evaporation is a cooling process. It requires energy.

Boiling vapor pressure = the external pressure Temperature is called the boiling point Normal Boiling point is the temperature a substance boils at 1 atm pressure. The temperature of a liquid can never rise above it’s boiling point Energy goes into breaking forces, not moving faster.

Changing the Boiling Point Lower the pressure (going up into the mountains). Lower external pressure requires lower vapor pressure. Easier to make bubbles

Changing the Boiling Point Raise the external pressure (Use a pressure cooker) Raises the vapor pressure needed. Harder to make bubbles Raises the boiling point.

Different Boiling points Different substances boil at different temperatures because they have different intermolecular forces Weak forces- lower boiling point

Gas to Liquid Phase Change Condensation Molecules stick together Releases energy.

Dynamic equilibrium Can occurs between condensation and evaporation 1. When first sealed the molecules gradually escape the surface of the liquid

Dynamic equilibrium 2. As the molecules build up above the liquid some condense back to a liquid.

Dynamic equilibrium 3. As time goes by the rate of vaporization remains constant 4. but the rate of condensation increases because there are more molecules to condense.

Dynamic equilibrium Rate of Vaporization = Rate of Condensation 5. Equilibrium is reached when Rate of Vaporization = Rate of Condensation Molecules are constantly changing phase “Dynamic” The amount of liquid and vapor remains constant “Equilibrium”

Vapor Pressure In a closed container the gas molecules will cause pressure. The pressure at equilibrium is called vapor pressure Different compounds have different vapor pressures because of different intermolecular forces Stronger forces, lower vapor pressure

Boiling/Evaporation (Vaporization) Liquid Critical Point Freezing Condensation Melting Boiling/Evaporation (Vaporization) Liquid 101.3 (kPa) Pressure (kPa) Normal Melting Point. (Tm) Normal Boiling Point. (Tb) Triple Point (All 3 states of Matter exist) Solid Gas Deposition Sublimation Temperature (°C)

Triple Point ~ point on a phase diagram that represents all three phases Normal Melting Point ~ melting point of a solid at a pressure of 101.3 kPa or 1atm Normal Boling Pont ~ boiling point of a liquid at a pressure of 101.3 kPa or 1atm Critical Point ~ distinction between the liquid and gaseous phases is almost non-existent

TP of Water

Triple Point CO2

TP Iodine

Sublimation

Gas Condenses Boiling Freezing Liquid Melting Solid Energy is put in from solid to gas (warms) Energy is removed from gas to solid (Cools)

Phase Diagrams Pressure ( atm) Temperature (°C) Solid/liquid Liquid/gas Solid/gas Temperature (°C)