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Lab 9 First Law of Thermodynamics
PHY250L
Student Name: Click here to enter text.
Kit Code (located on the lid of your lab kit): Click here to enter text.
“Pre-Lab Questions”
1. “Explain how the First Law of Thermodynamics relates to metabolism in humans.”
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2. “Initially there is a balloon that holds half of a mole of an ideal gas with a volume of 1.5 L at 273
K. Then 1500 J of heat is added to the balloon, and the balloon expands to 4.0 L. Using the Ideal
Gas Law (PV =nRT) where R = 8.314 J K-¹mol-¹, the equation for work, and the First Law of
Thermodynamics, what is the change in internal energy of the balloon at the end of the
process?”
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3. “A thermodynamic process that maintains a constant volume is called an isochoric process.
During these types of processes, the gas does no work because it is not increasing the volume of
the container. If you sealed off the top of a water bottle and shook 100 mL of water for two
minutes, you would find that the water is warmer when you take a drink. If you shook the water
long enough to raise the water’s temperature 5°C, what is the change in internal energy of the
system?”
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4. “Examine the pV– diagrams below. Which one has positive work being done, and which one has
negative work being done?”
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“Experiment 1: First Law of Thermodynamics”
“Post-Lab Questions”
Lab 9 First Law of Thermodynamics
PHY250L
1. “What did you observe as heat was added to the system over time? What did you observe as
the system cooled down?”
As heat was added to the system, the balloon expanded. Once the heat was removed the air
within the system cooled and contracted.
2. “Consider the balloon and air inside the flask to be a closed system. Use the First Law of
Thermodynamics to explain what happened to the balloon as heat was added by the
environment.”
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3. “Was the work done on the system positive or negative? Use your results to support your
answer.”
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4. “A scientist wants to do this experiment but modifies it by filling the balloon with 0.66 moles of
neon gas, which behaves as an ideal gas. If the balloon initially holds 0.4 L of the gas and
expands to 1.7 L after being heated in the pot over the stove, how much work is done by the
system if the experiment is performed at 273 K?”
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“Insert photo of your experimental setup with your name clearly visible in the background:”
“Experiment 2: Shaken Sand System”
“Table 1: Shaken Sand System Temperature Data””
“Initial Temperature (°C)“
26 C
“Final Temperature (°C)“
28 C
“Post-Lab Questions”
1. “What was the temperature change of the sand? Show your work.”
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Lab 9 First Law of Thermodynamics
PHY250L
2. “What was the change in internal energy of the system? Show your work.
Hint: The specific heat for dry sand is about 0.80 J/g·K and the density for sand is 2.3 g/mL.”
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3. “Another way to calculate the change in internal energy is to find the heat going into the system
using a different method. Use the following equation to find the heat going into the system:””
“and then multiply by the mass of the sand to find the change in internal energy of the system.
How does this compare to your answer above?
Hint: Cp,system is the specific heat capacity of the sand and T is the temperature of the system in
Kelvin.”
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4. “Explain where the heat energy is coming from, if there is no work being done on the system
because the volume is constant.”
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“Insert photo of your experimental setup with your name clearly visible in the background:”
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