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Vocab Quiz

Vocab Quiz. Answer directly onto the quiz paper Write the letter (A-H) next to the number. Lab make up time. If you missed the titration lab you must make it up. Tuesday, March 4 th during ‘A’ lunch Or Tuesday , March 4 th after school (2.20 – 2.50). Heat flow into and out of a system.

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Vocab Quiz

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  1. Vocab Quiz Answer directly onto the quiz paper Write the letter (A-H) next to the number

  2. Lab make up time If you missed the titration lab you must make it up. Tuesday, March 4th during ‘A’ lunch Or Tuesday , March 4th after school (2.20 – 2.50)

  3. Heat flow into and out of a system Endothermic Heat is absorbed by the system; the system feels cold to the touch http://www.youtube.com/watch?v=L-G7pLufXAo Exothermic Heat is given off into the surroundings; the system feels warm to the touch

  4. Materials & Procedure Beaker Thermometer Spoon Chemicals: NaCl Borax Urea CaCl2 • Fill 75 ml of water into the beaker • Measure the temperature of the water and record in table • Add ½ spoon of NaCl and stir • Measure and record temperature of solution and record in table • Rinse out beaker and repeat steps for all other chemicals

  5. Conclusion When the temperature of the solution increased it was an exothermic reaction. When the temperature of the solution decreased it was an endothermic reaction.

  6. Activities p. 559 Q a-c p. 561 Q 3, 4

  7. Thermochemical equation • Shows the energy change either as a reactant or a product • The energy change is also called ENTHALPY change ∆H.

  8. Exothermic Heat of Reaction CaO+ H2O  Ca(OH)2 + 65.2 kJ In order to use the equation correctly the physical state of the reactants and products must be given CaO(s) + H2 O (l)  Ca (OH)2 (s) ∆H = -65.2 kJ

  9. Endothermic Heat of Reactions 2 NaHCO3 (s) + 85 kJ --> Na2 CO3 (s) + H2O (l) + CO2 (g) Or 2 NaHCO3 (s)  Na2 CO3 (s) + H2 O(l) + CO2 (g) ∆H = 85 kJ

  10. Heats of Reaction Can be used to calculate enthalpy changes In order to do so you have to take into account how many moles of reactants are involved. If 2 moles of NaHCO3 require 85 kJ of heat then 4 moles of NaHCO3 will require twice as much (170 kJ)

  11. Physical changes use heats too! Heat of fusion

  12. Heat of vaporization

  13. Heat of condensation

  14. Heat of solution

  15. Heat of fusion • http://www.youtube.com/watch?v=jaaGqui9NVY

  16. Heat of Fusion of Ice The purpose of this lab is to estimate the heat of fusion of ice. Materials 100 ml graduated cylinder Hot tap water Foam cup Thermometer ice

  17. Procedure • Fil the graduated cylinder with hot tap water and let stand for 1 minute. Pour the water into the sink • Measure 70ml of hot water Pour the water into the foam cup. Measure the temperature of the water _____________oC • Add an ice cube to the cup of water. Gently swirl the cup. Measure the temperature of the water as soon as the ice cube has completely melted. _________o C • Pour water into graduated cyclinder and measure the volume ___________ ml

  18. Analyze and conclude • Determine the mass of the ice. [use the increase in volume of water and the density of water]. • Convert mass to moles. • Determine heat transferred from the water to the ice using the mass of the hot water, the specific heat of liquid water and the change in temperature. • Determine ∆H fusion by dividing the heat transferred from the water by the moles of ice melted. • Calculate % error by dividing your value of ∆H fusion by 6.01 kJ/mol and multiplying by 100.

  19. From heat of fusion to heat of vaporization. The molar heat of fusion is the heat absorbed by one mole of a solid as it melts. The molar heat of vaporization is the heat required to vaporize one mole of a given liquid.

  20. Predict When you melt ice and bring the water to the boil, what will the heating curve look like? temperature time

  21. Materials & Procedures Hot plate Beaker Ice thermometer Timer (stop watch) • Fill ½ beaker with ice 2. Insert thermometer into beaker and read temperature 3. Place beaker on hotplate and start heating up the beaker. 4. Record the temperature in the beaker every 30 seconds (use table)

  22. ………..Continue table until 3 minutes after water boils

  23. Draw a time/temperature graph • Does the graph look like you predicted it to look? • If not what was different? • What happens at 0o C and at 100o C?

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