Heat in Changes of State

GLE Heats of Fusion, Solidification, Vaporization, and Condensation Understanding a graph showing the heating curve of water Objective Student will classify, by type, the heat changes that occur during melting, freezing, boiling, and condensing.

Melting Ice An ice cube placed on a table in a warm room is the system and the table and air around it are the surroundings. The temperature of the ice remains at 0oC until all the ice has melted. The temperature of the water begins to increase only after all the ice has melted. Where have we discussed something similar?

Heats of Fusion and Solidification Molar Heat of Fusion Heat absorbed by one mole of a substance in melting from a solid to a liquid at a constant temperature ∆ H fus Molar Heat of Solidification Heat lost when one mole of a liquid solidifies at a constant temperature ∆ H solid

Heat of Fusion of Ice

Heat of Fusion Mini-Lab For the activity Hypothesis Experimental Plan/Experiment Data Analysis and Conclusions Conclusion Regarding Hypothesis Supported Not Supported Contradicted Give a connection for the activity with the real world

Heat of Fusion Mini-Lab For the activity Hypothesis – Ice melting results in measurable heat of fusion Experimental Plan/Experiment - Handout Data – (Model Mini-Lab) Analysis and Conclusions – Mini-Lab questions Conclusion Regarding Hypothesis Supported - Real world connection – re-useable cold pack.

Heat of Fusion Mini-Lab Calculations ∆ H = mH2O (g) x CH2O (J/g oC) X ∆T (oC) mH2O = 70 g (1 g = 1 mL) CH2O = 4.18 J/g oC ∆T = T (Warm Water) – T (Just After Ice Melts) ∆ H Fus = ∆ H / moles ice melted Moles ice melted = Mass Ice (g) x (1 mole H2O/18 g H2O)

Heats of Vaporization and Condensation Molar Heat of Vaporization Heat necessary to vaporize one mole of a give liquid ∆ H vap Molar Heat of Condensation Heat released when one mole of vapor condenses ∆ H cond

Heating Curve for Water

Heat of Solution Molar Heat of Solution Example ∆ H soln Heat changed caused by dissolution of one mole of a substance ∆ H soln Example CaCl2 (s) H2O (l) Ca 2+ (aq) + 2 Cl- (aq) ∆ H soln = - 82.8 kJ/mol Where did we see this used before?

Practical Application

Homework In Chapter 11 of Chemistry Text Sample problem 11-5 p. 311 Read the problem Work practice problem #22 Sample problem 11-6 p. 313 Work practice problem #24 Page 323 Problems # 64, 70, and 73