1. Physical Science Mr. Moss RHS

2.  When 2 states are present at the same time, we describe each as a phase.  Here, we see 2 phases of water: ◦ Solid Phase ◦ Liquid Phase

3.  A Phase Change is the reversible physical change that occurs when a substance changes from one state of matter to another.  There are 6 common phase changes ◦ Melting ◦ Freezing ◦ Vaporization ◦ Condensation ◦ Sublimation ◦ Deposition

4. Sublimation Deposition Melting Freezing Condensation Vaporization

5.  NOTE: ◦ The temperature of the substance DOES NOT change during a phase change!!!!  All phase changes are related to energy and temperature.

6.  Law of Conservation of Energy ◦ Neither created or destroyed. ◦ Transferred or Transformed  In phase changes, energy is either absorbed or released. ◦ Endothermic – energy is absorbed.  Ice melting ◦ Exothermic – energy is released.  Water freezing

9.  1g of ice absorbs 334 joules (J) of energy as it melts.  This amount of energy is the Heat of Fusion for water.  This is another term for the melting process.

13.  The Triple Point is where the substance exists in all 3 states.  The Critical Point is where, under extreme high temps and pressure, the liquid and gaseous states are indistinguishable.

14.  Water is a molecule made up of 2 atoms of Hydrogen and 1 atom of Oxygen.  The arrangement of molecules becomes less orderly as water melts.  The arrangement of molecules becomes more orderly as water freezes.

15.  Endothermic process  Heat energy is transformed into increased kinetic energy.  Causes molecules to vibrate more rapidly. ◦ Some gain enough to overcome the attractive forces and move from the fixed locations. ◦ This is the melting point.  Any energy gained after the phase change increases the average kinetic energy and the temperature rises.

16.  Exothermic  Average kinetic energy (Ke) decreases causing molecules to slow down.  At the freezing point, the attractive forces begin to draw the molecules into an orderly arrangement. ◦ Continues until all have been fixed.  Any energy removed after the phase change is complete decreased the average kinetic energy of the molecules and the temperature decreases.

17.  Vaporization happens when a substance changes from a liquid into a gas. ◦ Endothermic ◦ Heat of vaporization  Water gains 2258 J of energy when it vaporizes at 100° C. ◦ 2 vaporization processes  Boiling  Evaporation  Takes place at the surface of a liquid  Occurs at temps below the boiling point

18.  Process that changes a substance from a liquid to a gas at temps below the boiling point.  In a closed container: ◦ Water vapor collects above the liquid ◦ Pressure caused by molecules colliding with container is called vapor pressure.  Pressure increases as temp increases.

19.  As you apply heat energy, temperature and vapor pressure increase.  When vapor pressure = atmospheric pressure, the water boils.  Called the boiling point.  Depends on Atmospheric Pressure ◦ Higher elevations have less atmospheric pressure  Takes longer to cook food.

20.  The phase change in which a substance changes from a gas to a liquid.  The water vapor transferred heat to the glass and condensed into a liquid.

21.  Sublimation is the phase change from a solid to a gas without going through the liquid phase. ◦ Endothermic ◦ Dry Ice  Deposition is the phase change from a gas to a solid without going through the liquid phase. ◦ Exothermic ◦ Frost on windows