Important Terms & Notes

Feb. 24 & 25, 2014

Phases of Matter

• Phase: The State in which Matter exists at given Environmental and Energy conditions

• Five Phases of Matter: – Bose-Einstein Condensate, – Solid, – Liquid, – Gas, – Plasma.

Phase Changes

• The Change in the State of Matter due to an Increase or Decrease in Kinetic Energy.

• Phase changes depend on the Temperature and Pressure in which a given sample of matter exists. – How Hot or Cold the sample is.– How High or Low the Pressure is upon the sample.

Pressure

• Atmospheric Pressure– The amount of force (weight of the air) pressing

down upon the surface of the Earth due to the atmosphere.

• Vapor Pressure– The amount of force caused by the molecules of

the vapor (H2O) that exists above a liquid that presses down upon the liquid.

Standard Temperature & PressureSTP: US usage

• The condition at which the temperature of an environment is said to be 293°K or 20°C and the pressure is said to be 1 atmosphere.

(Pressure at sea level 14.7 lb/in² or 760 mmHg)

Equilibrium

• The condition when the transfer of Thermal Energy (Heat) and molecules of a substance is equal during the processes of Evaporation and Condensation.

– Thermal Equilibrium: The condition when two objects have reached the same temperature after the flow of heat from one to the other. No further transfer of heat is possible.

Evaporation

• The process of molecules in a substance (that is in the liquid state) gaining enough kinetic energy from the molecules below to allow the more energetic molecules to fly off into the space above the liquid.

• The molecules left behind in the liquid have LESS energy which results in a Cooling Process.

Condensation• The process of molecules in a substance (that is in

the gaseous state) losing enough kinetic energy to the environment or other molecules around them resulting in less energetic molecules and the formation of liquid droplets.

• Condensation is the Opposite of Evaporation.

• The molecules left behind in the environment have MORE energy which results in a Warming process.

Precipitation

• The process by which water droplets fall from clouds to earth.

• The process by which a more dense form of matter falls through a less dense form of matter i.e. (rain, snow, sleet through air)

Run-Off

• The Process in which Precipitation that has Fallen to the Ground Runs off higher elevations and collects in puddles, ponds, lakes, oceans at lower elevations.

Water Cycle Diagram

Boiling• The change of phase of molecules in the liquid

state to the gaseous state within the liquid.

• Unlike, evaporation which occurs at the surface of a liquid, boiling occurs within the liquid.– The molecules in the liquid state absorb sufficient

thermal energy to increase their vapor pressure to change state from liquid to gas forming bubbles which rise to the surface and escape into the space above the liquid

Boiling (continued)• The molecules in the liquid state absorb sufficient

thermal energy to increase their vapor pressure to change state from liquid to gas forming bubbles within the liquid which rise to the surface and escape into the space above the liquid

Approximate Boiling Temperatures of Water

Altitude Temperature

Sea Level 212 degrees F

984 ft. 210 degrees F

2,000 ft. 208 degrees F

3,000 ft. 206 degrees F

5,000 ft. 203 degrees F

7,500 ft. 198 degrees F

10,000 ft. 194 degrees F

20,000 ft. 178 degrees F

26,000 ft. 168 degrees F

Temperatures of water: High Altitude: Water boils at less than 212°F (approximately 96°F). Each 500 foot increase in altitude causes a drop of about 1° in the boiling point.

Heat of Vaporization

• The amount of heat required to change the phase of 1 gram of a substance in liquid form into 1 gram of vapor.

» Q = mL

• For H20: L = 540 cal/g

Freezing

• The change of phase of molecules in the liquid state to the solid state.

• The process occurs through the extraction of kinetic energy from the liquid sample until the molecules of the substance arrange themselves within a crystalline lattice structure peculiar to the sample.

Water exhibits a six-sided ice crystal.

Heat of Fusion

• The amount of heat given up to change the phase of 1 gram of a substance in liquid form into 1 gram of solid (crystal/ice).

» Q = mL

• For H20: L = 80 cal/g

Regelation• The melting of a substance under increasing pressure

and then the refreezing of the substance when the pressure is reduced.

• For water, the ice crystals are literally being crushed into the liquid state then being allowed to freeze again.

• An example: Cars in winter traveling over snow when the ambient temperature is -10 °C. The weight of the car (Pressure) “melts” the snow. Then after the car passes the “melted” snow freezes turning the roadway into a sheet of ice. (Very Slippery!)

Relative Humidity

• The amount of water vapor that is contained in the atmosphere at a given temperature and pressure.

Saturated• The condition when the atmosphere can no

longer hold any additional increase in water vapor.

• The term also applies to any gas and its ability to hold any additional vapor whether water or other substance in the gaseous form.