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Warm Up:

Warm Up:. Which substance has a definite shape and a definite volume at STP? NaCl ( aq ) Cl 2 ( g) CCl 4 ( l ) AlCl 3 ( s). At STP, which element has a definite shape and volume? (a) Ag (b) Hg (c) Ne (d) Xe. At A , T or KE increases and PE is constant.

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Warm Up:

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  1. Warm Up: • Which substance has a definite shape and a definite volume at STP? • NaCl (aq) • Cl2 (g) • CCl4(l) • AlCl3 (s)

  2. At STP, which element has a definite shape and volume? (a) Ag (b) Hg (c) Ne (d) Xe

  3. At A, T or KE increases and PE is constant. At B, the ice starts to melt at 0 C. T or KE is constant and PE increases until all the ice is melted. At C, T or KE increases and PE is constant. At D, the water starts to boil at 100 C. KE is constant and PE increases until all the water evaporated. At E, T or KE increases and PE is constant.

  4. At E, T or KE decreases and PE is constant. At D, the water vapor starts to condense. T or KE is constant and PE decreases until all the gas is condensed. At C, T or KE decreases and PE is constant. At B, the water starts to freeze at 0 C. T or KE is constant and PE decreases until all the water is frozen. At A, T or KE decreases and PE is constant.

  5. Temperature Scale • Temperature: measure of average kinetic energy

  6. Convert from Celsius to Kelvin C + 273= K Practice • What temperature is equal to -73 C? 200 K

  7. Absolute Zero Point at which molecules do not move

  8. What temperature is equal to 20 K? • -253 C • -293 C • 253 C • 293 C

  9. When the temperature of an object changes by 100 C, the same temperature change in Kelvins would be • 100 K • 173 K • 273 K • 373 K

  10. Heat • Is a measure of the amount of energy transferred from one substance to another • Measured in calories or Joules • Heat flows from high to low 303 K 313 K

  11. Equilibrium Endothermic= absorbed energy 308 K 308 K Exothermic= released energy

  12. Measurement of Heat Energy • Amount of heat given off or absorbed in a reaction can be calculated

  13. How many joules are absorbed when 50.0 grams of water are heated from 30.2 C to 58.6 C? q = (50 g) (4.18 J/ g C) (Tf- Ti) q = (50 g) (4.18 J/ g C) (58.6 C-30.2 C) q= 5936 J or 5.936 KJ q= 5940 J

  14. How many kilojoules of heat energy are absorbed when 100.0 g of water are heated from 20.0 C to 30.0 C? q= (100.0 g) (4.18 J/ g C) (30.0 C- 20.0 C) q = 4180 J = 4.18 KJ

  15. Heat of Fusion • Amount of heat needed to convert a unit mass of a substance from solid to liquid at its melting point (Water)

  16. How many joules are required to melt 255 g of ice at 0 C? q= (255 g) (334 J/g) q= 85170 J = 85200 J

  17. Heat of Vaporization • Amount of heat needed to convert a unit mass of a substance from its liquid phase to its vapor phase at constant temperature (Water)

  18. How many joules of energy are required to vaporize 423 g of water at 100 C? q= (423 g) (2260 J/g) q= 955980 J = 956000 J

  19. Combination Problems How many joules are needed to change 20.0 grams of ice to water from 0.00 C to 80.0 C?

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