Physics SL

IB Physics Experiment: Specific Heat Capcity of Water

Research Question

What is the specific heat capacity of water?

Hypothesis

The water should have the specific heat capacity of 4180 Jkg-1K-1

Theoretical Background

The official specific heat capacity of water is about 4180 Jkg-1K1. The specific heat capacity is the amount of heat per unit mass which is required to raise the temperature by one degree Celsius. Using the formula Q=mcΔT we can find the specific heat capacity (c) by finding out the mass (m), the change in temperature (ΔT), and heat in joules or kinetic energy of molecules (Q).

Variables

  1. Independent Variable : Specific Heat Capacity
  2. Dependent Variable   :  Water (use distilled water)
  3. Controlled Variable  :  Amount of water in beaker (500ml)

Materials & Equipment

  1. Vernier Lab Pro
  2. Stainless Steel Temperature Probe
  3. Logger Lite (software)
  4. Electric water heater
  5. Aluminum Foil
  6. Beaker
  7. Digital scale
  8. Distilled Water

Procedures

  1. Find the power of the water heater (on the packaging)
  2. Measure the mass of the beaker (without water) and write it down
  3. Add 500ml of distilled water into the beaker
  4. Measure the mass of the beaker with water added and write it down
  5. Calculate the mass of water (mass of beaker with water – mass of beaker)
  6. Wrap the beaker with water with aluminum foil while leaving space to insert the heater and the temperature
  7. Set up LabPro with the stainless temperature probe attached and plug it to the computer.
  8. Start data collection software (Logger Lite)
  9. Insert the temperature probe into the water and the heater into the water (do not turn it on yet)
  10. Start data logger software
  11. Start water heater
  12. Wait until the logger is done recording (180 seconds)
  13. Save the log and calculate the heat capacity by using the formula

Q=mcΔT

Q/Δt = mcΔT/Δt

P = mcΔT/Δt

  1. Repeat the experiment two more times

Data

  1. Mass of water = 0.4855 kg
  2. Time = 180 seconds (3 minutes)
  3. Heater Power = 350W

Trial 1

= 15088.73614

Trial 2

= 6620.567898

Trial 3

= 16852.35465

Trial 4

= 3850.538006

Average

Trial 1 Trial 2 Trial 3 Trial 4 Average
15088.73614 6620.5679 16852.35465 3850.538006 10603.04917 Jkg-1K-1

 

Analysis

From the data received above, it seems like there are more errors than it is accurate. The experiment resulted in an inconclusive result.

Uncertainity and Error

  • Temperature probe has a long surface area meaning that it averages the value of the temperature
  • Sometimes the temperature probe gets in contact with the beaker or heater
  • The heater needs time to warm up for its full potential
  • The heater doesn’t consistently heat up (sometimes it cools down, then heats up again)
  • After using the heater, let the heater cool down so that it doesn’t heat up with it’s full potential again
  • Heat loss through surrounding
  • Heat might not mix throughout the water (causing inaccuracy for the temperature probe)

 

Conclusion

Even though the experiment seems easy to do and is straightforward, it was harder than it seems. The data shown above cannot prove the hypothesis that water should have a specific heat capacity of about 4180 Jkg-1K1 to be true. This is most likely caused by the wrong apparatus used such as the heater which didn’t put consistent heat. It could also have been impacted by the loss of heat by the surroundings plus the addition of inaccuracy. This experiment resulted in an inconclusive result. This experiment could be improved to show a more accurate result by using apparatus which is better and more accurate and by modifying the experiment procedures such as having temperature probe and the heater should have some kind of static holder so that it will stay in the same spot.

 

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