13b-heat-of-fusion - CHM151LL: HEAT OF FUSION FOR ICE | 1...

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Unformatted text preview: CHM151LL: HEAT OF FUSION FOR ICE | 1 Heat of Fusion for Ice OBJECTIVES: • Become familiar with the thermodynamics of phase changes for a pure substance • Practice mass and temperature measurement techniques • Calculate the molar enthalpy of fusion for ice DISCUSSION: Melting and freezing behavior are among the characteristic properties that give a pure substance its unique identity. As energy is added, pure solid water (ice) at 0 °C changes to liquid water, without a temperature change. In this lab exercise, you and a partner will determine the energy (in joules) required to melt one gram of ice. You will then determine the molar heat of fusion for ice (in kJ/mol). Excess ice will be added to warm water, at a known temperature, in a Styrofoam cup calorimeter. The warm water will be cooled to temperature near 0 °C by the ice. The energy required to melt the ice is removed from the warm water as it cools. To calculate the amount of heat flow from the water, use the relationship: q = s ! m ! ! T (1) where q stands for heat flow (in J), s is the specific heat (in J/g · °C), m is mass in grams, and ∆ T is the change in temperature (in °C). For liquid water, s = 4.18 J/g · °C. PROCEDURE: 1. Support a Styrofoam cup in a 250-mL beaker. 2. Obtain 7 or 8 large ice cubes, and keep them ready. 3. Heat 250 mL of water to about 60 °C. Use a graduated cylinder to measure 100 mL of the hot water into the cup. Record this as V 1 . 4. Lower the temperature probe into the hot water (to about 1 cm from the bottom of the cup). 5. Wait for the temperature reading to reach a maximum (it will take some time for the probe to reach the temperature of the water). Record this initial reading as T 1 on your data sheet. 6. Remove excess liquid from the ice by shaking or patting with a paper towel. Add the ice to the hot water. Begin recording the temperature reading every 20 s....
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This note was uploaded on 02/28/2012 for the course CHEM 151 taught by Professor Wiley during the Spring '12 term at Mesa CC.

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13b-heat-of-fusion - CHM151LL: HEAT OF FUSION FOR ICE | 1...

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