1. Is freezing endothermic or exothermic? Explain what is happening on the molecular level 2. Is vaporization endothermic or exothermic? Explain what is happening on the molecular level.

Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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Chem 105-Online
Safety:
Remember, Hot glass looks the same as cold glass!!! You will also want to ensure that the tubing
used does not come into contact with the heating element. The tubing will also get VERY hot.
Steam carries more energy at the same temperature than boiling water-so use of hot hands and
precautions is a must! With the use of hot hands, please be sure that if you are using a flame to
use additional caution.
Prelab:
1. Is freezing endothermic or exothermic? Explain what is happening on the molecular level.
2. Is vaporization endothermic or exothermic? Explain what is happening on the molecular
level.
Procedure: Part A-Heat of Fusion.
1. Obtain the mass of your coffee cup calorimeter.
2. Fill the foam cup about 3/4 full with tap water and determine the mass of the water as
mw on the data sheet.
3.
Set up the foam cup, beaker, and the thermometer as shown.
4. Lower the thermometer into the water (to about 1.0 cm from the bottom).
5. Obtain the initial temperature of the water. This is T1 in your data table.
6. Obtain about 5-6 small ice chunks if crushed ice. If you are working with cubes, I should
be sufficient. If the ice does not melt, redo the trial with less ice so it sufficiently melts.
7. Shake excess water from the small ice cubes or dry them with a paper towel, then add
them to the water. Obtain the mass of the ice by massing by difference. You want
approximately 10grams of ice.
9.
8. Stir gently with the thermometer the temperature. Take readings every 30 seconds.
When the ice is completely melted, stir the mixture one more time and note this
temperature as the final temperature, T2.
10. Use the balance to obtain the mass of the cup + water + melted ice. Record this value.
11. Subtract T₁-T₂ to determine AT, the change in water temperature. Record this value.
12. Subtract the mass of the cup
water, from the cup + water + melted ice to obtain the
mass of the ice. Record this value in as (mi).
13. The total amount of heat energy lost by the water (Q2) is equal to the amount of heat
energy absorbed by the ice as it melted (Q3), plus an additional amount of energy
required to bring the temperature to equilibrium (Q₁). In other words, Q1 represents the
energy needed to raise the temperature of the melted ice water to the final
temperature.
Transcribed Image Text:Chem 105-Online Safety: Remember, Hot glass looks the same as cold glass!!! You will also want to ensure that the tubing used does not come into contact with the heating element. The tubing will also get VERY hot. Steam carries more energy at the same temperature than boiling water-so use of hot hands and precautions is a must! With the use of hot hands, please be sure that if you are using a flame to use additional caution. Prelab: 1. Is freezing endothermic or exothermic? Explain what is happening on the molecular level. 2. Is vaporization endothermic or exothermic? Explain what is happening on the molecular level. Procedure: Part A-Heat of Fusion. 1. Obtain the mass of your coffee cup calorimeter. 2. Fill the foam cup about 3/4 full with tap water and determine the mass of the water as mw on the data sheet. 3. Set up the foam cup, beaker, and the thermometer as shown. 4. Lower the thermometer into the water (to about 1.0 cm from the bottom). 5. Obtain the initial temperature of the water. This is T1 in your data table. 6. Obtain about 5-6 small ice chunks if crushed ice. If you are working with cubes, I should be sufficient. If the ice does not melt, redo the trial with less ice so it sufficiently melts. 7. Shake excess water from the small ice cubes or dry them with a paper towel, then add them to the water. Obtain the mass of the ice by massing by difference. You want approximately 10grams of ice. 9. 8. Stir gently with the thermometer the temperature. Take readings every 30 seconds. When the ice is completely melted, stir the mixture one more time and note this temperature as the final temperature, T2. 10. Use the balance to obtain the mass of the cup + water + melted ice. Record this value. 11. Subtract T₁-T₂ to determine AT, the change in water temperature. Record this value. 12. Subtract the mass of the cup water, from the cup + water + melted ice to obtain the mass of the ice. Record this value in as (mi). 13. The total amount of heat energy lost by the water (Q2) is equal to the amount of heat energy absorbed by the ice as it melted (Q3), plus an additional amount of energy required to bring the temperature to equilibrium (Q₁). In other words, Q1 represents the energy needed to raise the temperature of the melted ice water to the final temperature.
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