1. The melting point of pure iron is 1505 degrees Celcius. What Fahrenheit temperature is this?
2. The melting point of ethyl alcohol is -179 degrees Fahnrenheit. What is the Celcius temperature?
3. Find the amount of heat in kcal generated by 7510 J of work.
4. Find the mechanical work equivalent (in kJ) of 8550 cal of heat.
5. A small bag of potato chips has a mass of 28 g and contains 150 kcal. How much work (in kJ) must a person do to offset eating the bag of chips?
6. How many BTU of heat are given off by 500.lb of aluminum when it cools from 650.° F to 75°F?
7. How many kilocalories of heat must be added to 750. kg of steel to raise its temperature from 75°C to 300°C?
8. A block of copper is heated from 20.0 C to 80.0 C. How much heat (in J) is absorbed by the copper if its mass is 60.0 g?
9. How many pounds of ice at 32 F can be melted by the addition of 635 BTU of heat?
10. How many kilocalories of heat are required to melt 20.0 kg of ice at 0.0 C?
11. Change 24.0°C to Kelvin.
12. Change 500.°C to Fahrenheit.
13. Find the amount of heat in cal generated by 100. J of work.
14. A single M&M has 3.44 kcal of energy. How much work (in J) must a person do to “work off” eating a single M&M?
15. A block of copper (c = 390 J/kg°C) is heated from 20.0 C to 60.0 C. How much heat (in J) is absorbed by the copper if its mass is 45.0 g?
16. How many kilocalories of heat are required to melt 125 g of ice at 0.0°C? (Assume ice has Lf = 80.0 kcal/kg)
17. An aluminum plug (a = 2.3 x 10-5/C°) has a diameter of 10.003 cm at 40.0 °C. At what temperature (in Celcius) will it fit precisely into a hole of constant diameter 10.000 cm?
18. A steel pipe (a = 6.5 x 10-6/F°) has a cross sectional area of 127.20 in2 at 25°F. What is its cross sectional area (in in2) when the pipe is heated to 175°F?
19. Find the increase in volume (in L) of 35 L of acetone heated from 28°C to 38°C. (Acetone has a ß = 1.49 x 10-3/C°)
20. A small amount (18.0 g) of an unknown metal is placed into a calorimeter with 180. g of water (c = 1.00 cal/gC). The water is initially at a temperature of 20.0 C and the metal is initially at 95 C. The calorimeter reaches a final temperature of 22.0 C. What is the specific heat (in cal/gC) of the unknown metal?
PH 115 Online Lab 14: Calorimetry
OBJECTIVES
1. To use the method of mixtures to determine the specific heat of an unknown material.
INTRODUCTION
• You may have noticed that we skipped section 14.5 of our textbook. By completing this lab, we will cover the method of mixtures that we skipped earlier in the lesson.
• Open this calorimeter simulation and for use in this lab (http://www.chemfiles.com/flash/calorimeter.swf).
• A calorimeter is an insulated container filled with a liquid, usually water. When a hot object is placed in the calorimeter, heat energy is transferred from the object to the water and the water heats up. Calorimeters can be used to find a substance’s specific heat capacity. You will use this calorimeter simulation to determine the specific heat capacity of the unknown metal used in the simulation.
• In the simulation, set the mass of water to 80.0 g and the mass of the metal to 20.0 g.
• Also set the water temperature to 15.00 °C and the metal temperature to 100.00 °C.
• Click the start button and watch as the temperature of the water changes. After a few moments, it should reach roughly a constant value.
• What was the final temperature of the water?
• Now that the metal’s temperature is in equilibrium with the water, how much did the metal’s temperature change from beginning to end?
• How much did the water’s temperature change from beginning to end?
• Specific heat capacity can be described as a substance’s resistance to temperature changes. Which substance has a greater specific heat capacity: the metal or the water? Explain.
HEAT TRANSFER
Now we will explore the factors that determine how energy transfers between objects.
Predict:
• How do you think increasing the water’s mass would affect the final temperature?
• How do you think decreasing the metal’s mass would affect the final temperature?
• How do you think increasing or decreasing the metal’s initial temperature would affect the final temperature?
Collect Data:
• Use the simulation to determine the final temperature for each set-up in the table below. In each case, we will compare the results to our initial test.
Water Metal Final Temp
(°C)
Initial Temp (°C) Mass (g) Initial Temp (°C) Mass (g)
15.00 80.0 100.00 20.0 16.91
15.00 150.0 100.00 20.0
15.00 80.0 100.00 20.0 16.91
15.00 80.0 100.00 40.0
15.00 80.0 100.00 20.0 16.91
15.00 80.0 90.00 20.0
15.00 80.0 130.00 20.0
Analyze:
• Using the results from your table, explain how the final temperature changed and why you think the change occurred.
• What was the effect of increasing the water’s mass? Why?
• What was the effect of decreasing the metal’s mass? Why?
• What was the effect of changing the initial temperature of the metal? Why?
• The amount that the water’s temperature increases depends on the mass of the water and the amount of heat energy in the metal.
• How does changing the initial mass of the mass affect how much heat energy it has?
• How does changing the initial temperature of the metal affect how much heat energy it has?
SPECIFIC HEAT MEASUREMENT
• Read through section 14.5 of the textbook, including the example problems.
• Watch this video showing a worked example problem. (http://youtu.be/dGkOXiv_xOY)
• Collect final temperature data from the simulation and enter it in the table below.
• Calculate the specific heat of the unknown metal for all five measurements.
• Compute the average and average deviation of the specific heat.
• Compare your specific heat to Table 15 of Appendix C in our textbook.
• Try to identity the unknown metal.
Water Metal
specific heat
(cal/g °C) mass
(g) Tinitial
(°C) Tfinal
(°C) specific heat
(cal/g °C) mass
(g) Tinitial
(°C) Tfinal
(°C)
1.00 80.0 15.00 10.0 100.0
1.00 100.0 20.00 15.0 120.0
1.00 120.0 25.00 25.0 140.0
1.00 140.0 30.00 35.0 160.0
1.00 150.0 35.00 45.0 180.0
Specific Heat:
Average Avg. Deviation Possible Metal(s)
