1. Chapter 13

2.  All matter has mass and volume  Matter is made up of molecules which are the smallest part of a substance that can still be identified as that substance

3. Definite ShapeChanges Shape Definite Volume Changes Volume SolidLiquid Gas

5.  A change of state is the conversion of a substance from one physical form to another  All changes of state are physical changes

6.  During a change of state, the energy of a substance changes.  The energy of a substance is related to the motion of its molecules.  The molecules in liquid water move faster than the molecules in ice. Therefore, liquid water has more energy than ice.

7.  If energy is added to a substance, what happens to its molecules?  If energy is removed, what happens? They move faster They move slower

8.  Temperature is the measure of the speed of a substance’s molecules and therefore a measure of its energy.

9.  Solid  Liquid  For solids to melt, it must absorb energy to increase the motion of the molecules until they can overcome the attraction between them  This is known as an endothermic change because energy is absorbed by the substance as it changes state

10.  Liquid  Solid  For a liquid to freeze, the motion of its molecules must slow down to the point where attractions between them overcome their motion  This is known as an exothermic change because energy is removed from, or taken out of, the substance as it changes state

11.  Freezing can occur at high or low temperatures. Magnesium freezes at 650° C while water freezes at 0°C

12.  True or False:  Evaporation can occur at any temperature.  Boiling occurs only at the surface of a liquid.  Vaporization is simply a liquid changing to a gas. True False True

13.  Vaporization: Liquid  Gas  Boiling: vaporization that occurs throughout a liquid  Evaporation: vaporization that occurs at the surface of a liquid before it’s boiling  Self-check: Is vaporization an endothermic or exothermic change?

15.  Gas  Liquid  Large numbers of molecules must clump together. This happens when the attraction between molecules overcomes their motion.  Energy must be removed from the gas to slow the molecules down  Exothermic change

17.  Solid  Gas  Molecules move from being very tightly packed together to being spread very far apart. The attractions between the molecules must be completely overcome.  Because this requires the addition of energy, it is an endothermic change.

19. Change of StateDirection Endothermic or Exothermic? Example MeltingSolid  LiquidEndothermicIce melts into liquid water at 0° C FreezingLiquid  SolidExothermicLiquid water freezes into ice at 0°C VaporizationLiquid  GasEndothermic Liquid water vaporizes into steam at 100°C CondensationGas  LiquidExothermic Steam condenses into liquid water at 100°C SublimationSolid  GasEndothermicSolid dry ice sublimes into a gas at -78°C

21.  Compare endothermic and exothermic changes.  How are evaporation and boiling different? How are they similar?