Name Period Date 11. Specific Heat Driving Questions Some substances take a long time to get hot even though they are receiving the same amount of energy. If the flow of energy to two different substances with equal mass is the same, why does one have a higher temperature than the other? Background Energy comes in two major classifications, potential and kinetic. Potential energy is stored, waiting to be released. Once that energy is released, it is set in motion; this is known as kinetic energy. Heat is one form of kinetic energy. Energy is measured in units of calories (cal) or joules (J) and describes the total amount of molecular motion in a sample. Temperature is different from heat. Heat energy is used to increase the temperature of a substance. Temperature is a measure of the average energy a particle has within a sample. Some substances require more energy to stimulate motion than others. Specific heat is the amount of energy required to increase the temperature of 1 gram of a substance by 1 ºC (molar heat capacity is similar, but for 1 mole of a substance). Different substances require different amounts of energy to increase temperature, as shown in Table 1 below. A calorimeter is an apparatus that traps energy inside a closed container. By using the energy released from a substance to warm surrounding water inside the calorimeter, the amount of energy transferred can be measured. This is done by comparing the temperature change of both the water and the substance. Table 1: Specific heat and molar heat capacity of water and select metals Substanc e Specific Heat (J/(g×°C)) Molar Heat Capacity (J/(mol×°C)) Aluminum 0.902 24.3 Copper 0.385 24.5 Gold 0.129 25.4 Iron 0.450 25.1 Lead 0.129 26.7 Nickel 0.444 26.1 1
Transcript
Name Period Date
11. Specific Heat
Driving QuestionsSome substances take a long time to get hot even though they are receiving the same amount of energy. If the flow of energy to two different substances with equal mass is the same, why does one have a higher temperature than the other?
BackgroundEnergy comes in two major classifications, potential and kinetic. Potential energy is stored, waiting to be released. Once that energy is released, it is set in motion; this is known as kinetic energy. Heat is one form of kinetic energy. Energy is measured in units of calories (cal) or joules (J) and describes the total amount of molecular motion in a sample.
Temperature is different from heat. Heat energy is used to increase the temperature of a substance. Temperature is a measure of the average energy a particle has within a sample. Some substances require more energy to stimulate motion than others. Specific heat is the amount of energy required to increase the temperature of 1 gram of a substance by 1 ºC (molar heat capacity is similar, but for 1 mole of a substance). Different substances require different amounts of energy to increase temperature, as shown in Table 1 below.
A calorimeter is an apparatus that traps energy inside a closed container. By using the energy released from a substance to warm surrounding water inside the calorimeter, the amount of energy transferred can be measured. This is done by comparing the temperature change of both the water and the substance.
Table 1: Specific heat and molar heat capacity of water and select metals
Substance
Specific Heat(J/(g×°C))
Molar Heat Capacity(J/(mol×°C))
Aluminum 0.902 24.3
Copper 0.385 24.5
Gold 0.129 25.4
Iron 0.450 25.1
Lead 0.129 26.7
Nickel 0.444 26.1
Silver 0.235 25.3
Tin 0.228 27.1
Water 4.184 75.3
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Specific Heat
Zinc 0.386 25.2
Materials and Equipment
For each student or group:
Data collection system Tongs
Fast response temperature sensor Polystyrene cup (2)
Beaker, 250-mL Lid for the polystyrene cup
Beaker, 400-mL Paper towels
Graduated cylinder, 100-mL Tap water, 250 mL
Balance, centigram Distilled (deionized) water, 200 mL
Thermometer (or stainless steel temperature sensor) Metal sample, unknown, up to 4 x 4 x 4 cm
Hot plate
SafetyAdd these important safety precautions to your normal laboratory procedures:
Be aware that boiling water and steam can cause painful burns.
Avoid coming in contact with hot equipment and glassware.
Sequencing ChallengeThe steps below are part of the Procedure for this lab activity. They are not in the right order. Determine the proper order and write numbers in the circles that put the steps in the correct sequence.
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Transfer the metal to the calorimeter and continue to collect data until the temperature stabilizes.
Place a temperature sensor in the colorimeter and start recording temperature data.
Add 100 mL of distilled water to the calorimeter and find the mass of calorimeter and water together.
Heat the metal in boiling water.
As the metal is being heated in the boiling water, construct the calorimeter and find the mass of the empty calorimeter.
Student Inquiry Worksheet
ProcedureAfter you complete a step (or answer a question), place a check mark in the box () next to that step.
Note: When you see the symbol "�" with a superscripted number following a step, refer to the numbered Tech Tips listed in the Tech Tips appendix that corresponds to your PASCO data collection system. There you will find detailed technical instructions for performing that step. Your teacher will provide you with a copy of the instructions for these operations.
Set Up
1. Start a new experiment on the data collection system. �(1.2)
2. Connect a fast response temperature sensor to the data collection system. �(2.1)
3. Create a graph display of Temperature (°C) versus Time (s). �(7.1.1)
4. Heat 250 mL of tap water in a 400-mL beaker on a hot plate to boiling.
5. Construct a simple calorimeter by placing one polystyrene cup into another polystyrene cup.
Collect Data
6. Describe the metal sample (color, luster, density).
13. Place the fast response temperature sensor into the calorimeter, making sure it is submerged in the water.
14. Using a thermometer (or stainless steel temperature sensor), record the temperature of the boiling water and record the value in degrees Celsius in Table 2 above.
CAUTION: The fast response temperature sensor is not designed for temperatures above 70 °C.
15. What is the temperature of the metal sample in the boiling water?
27. Use the tongs to remove the metal from the calorimeter and dispose of the water.
28. Repeat the steps in the Collect Data section, recording the values in the second trial column in Table 2 above.
29. Name the data run as “metal trial 2”. �(8.2)
30. Save your data file and clean up according to the teacher's instructions. �(11.1)
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Specific Heat
Data Analysis
1. Use the graph of Temperature (°C) versus Time (s) to determine the final temperature, initial temperature, and change in temperature (∆T) for the water in the calorimeter. Follow the steps below to complete this on your data collection system:a. Display the run of data you want to analyze. �(7.1.7)
b. Measure the difference between the final temperature and the initial temperature. When this step is complete, the final temperature, initial temperature, and change in temperature will be displayed on the screen. �(9.2)
c. Record the values for each trial in Table 3 below.
Table 3: Temperature changes in the calorimeter
Parameter Trial 1 Trial 2
Tfinal (˚C) of water in the calorimeter
Tinitial (˚C) of water in the calorimeter
ΔT = Tfinal – Tinitial (˚C)
2. ¨ Create a graph with both runs of data displayed on your data collection system. �(7.1.3)
3. Sketch or print a copy of the graph of Temperature (°C) versus Time (s) for both trials of data. Label each trial as well as the overall graph, the x-axis, the y-axis, and include numbers on the axes. �(11.2)
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Student Inquiry Worksheet4. ¨ Calculate the mass of water in the calorimeter for each trial. Record your answers
in Table 4 below.
Table 4: Mass of water in the calorimeter
Parameter Trial 1 Trial 2
Mass of 250-mL beaker and calorimeter, with water (g)
Mass of 250-mL beaker and calorimeter, empty (g)
Mass of the water (g)
5. ¨ Determine the amount of energy in Joules transferred from the metal block to the water using the information provided below. Show your work in Table 5 below.
q = energy transferred
m = mass of water in the calorimeter
c = specific heat of water = 4.184 J/(g×°C)
∆T = change in temperature in the colorimeter
Table 5: Calculating energy in joules transferred
Parameter
Trial 1 Trial 2
Show your work here
Joules transferred (J)
6. ¨ Calculate the temperature change for the metal sample. Record the answer in Table 6 below.
Table 6: Change in temperature of the unknown metal
Parameter Trial 1 Trial 2
Tinitial(˚C) of the metal (in the boiling water)
Tfinal (˚C) of the metal (in the calorimeter at the end of the experiment)
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Specific Heat
ΔT = Tinitial – Tfinal (˚C)
7. ¨ Using the mass of the metal sample, its temperature change, and the number of joules of energy transferred to the water, calculate the specific heat of the metal sample for each trial and then find the average of the two trials. Show your work in Table 7 below.
c = specific heatq = energy transferredm = mass of the unknown metal∆T = change in temperature of the metal
Table 7: Calculating specific heat
Parameter Trial 1 Trial 2
Show your work here:
Specific heat (J/(g×°C))
Average specific heat (J/(g×°C))
Analysis Questions
1. What is the identity of the metal you used in this experiment? (Use Table 1 in the Background section and the color, luster, and density you described from the question at the beginning of the Collect Data section of the Procedure.)
Specific Heat5. Brass is an alloy of copper and zinc. What is the specific heat of a sample of brass weighing 11.8 g if it requires 197.1 J to increase its temperature by 44.3 ºC?
6. What is the final temperature if 100.0 mL of water at 10.0 ºC absorbed 1000 J?
Multiple Choice QuestionsSelect the best answer or completion to each of the questions or incomplete statements below.
1. How many joules are required to increase the temperature of a 30.0 g block of gold from 25.0 ºC to 50.0 ºC? The specific heat of gold is 0.129 J/(g×°C).
A. 4.184 JB. 96.8 JC. 193.5 JD. 3138 J
2. Which of the following describes substances with lower values for specific heat?
A. Better conductors of heatB. Better insulators of heatC. Worse conductors of heatD. None of the above
3. Finding a specific heat of 0.233 J/(g×°C) probably indicates a sample of what metal?
A. AluminumB. NickelC. SilverD. Tin
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Student Inquiry Worksheet4. What calculation converts specific heat to molar heat capacity?
A. Multiply by the mass of the sampleB. Divide by the mass of the sampleC. Multiply by the molar massD. Divide by the molar mass
5. What is the specific heat of iron in cal/(g×°C)?
A. 0.108B. 0.450C. 1.88D. None of the above
Key Term ChallengeFill in the blanks from the list of words in the Key Term Challenge Word Bank.
1. Energy is classified in one of two ways: ____________ (stored energy) and ____________ (energy in motion). ____________ is a form of energy in motion. It is measured in calories or joules. Heat is a measure of the change in the ____________ amount internal energy in a sample. Temperature is different from heat. It is measured in units of kelvin or degrees Celsius. Temperature is the ____________ amount of molecular motion in a sample.
2. Heat energy is used to increase the temperature of a substance. The amount of heat required to raise the temperature of ________________________ of substance by ________________________ is called the ________________________. For example, one gram of lead requires 0.129 J of energy to increase its temperature from 24.0 to 25.0 ºC. The amount of heat required to raise the temperature of one mole of substance by one degree Celsius is called ________________________.
3. The amount of heat transferred can be trapped inside a ________________________. This device insulates the system being studied from its surroundings. Most often, water is inside the calorimeter. Because this substance has a specific heat of ________________________, it can absorb a lot of energy with a ________________________ change in temperature. By measuring the increase in the temperature of the water, the amount of energy transferred inside the calorimeter can be determined.
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Specific Heat
Key Term Challenge Word BankParagraph 1 Paragraph 2 Paragraph 3average
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