Science Homework Help

Experiment 12

Experiment 23 in lab manual

Determination of Specific Heats

Objective: To determine the specific heat and the molar heat capacity of various metals.

Equipment: Device with Internet connection, calculator, Word and Excel software

For further “Specific Heat” information:

Specific heat and latent heat of fusion and vaporization

https://www.khanacademy.org/science/ap-chemistry/t…

Calorimetry

https://www.youtube.com/watch?v=yhNHJ7WdT8A&list=PLybg94GvOJ9EbbO2RXPWTUNIIE0C7hSfm&index=24

Simulation: Specific Heat

https://media.pearsoncmg.com/bc/bc_0media_chem/che…

Essential requirements for a complete lab report

A. Complete the 7 pre-lab questions

B. Complete the main assignment by using the simulation to generate 4 sets of data

to determine specific heat, atomic mass, and name of unknown metals _.

C. Complete 3 Post-Lab questions

D. Conclusion

Important equations:

m₁cp₁∆T₁ + m₂cp₂∆T₂ = 0

atomic mass x specific heat (cp)= 26 J deg-1 mol-1 . (For estimated atomic mass)

Molar Heat Capacity = Cp = cp₁ x atomic mass of the element

cp_w = specific heat of water = (4.184 J/g ºC)

Appendix A:

Activity	Lab#12 Rubric	Total Score 100
Pre-lab questions		14 pts
	Simulation	15 pts
Experiment Activity	Data chart	25 pts
	Calculations	15 pts
		55 pts
Post-lab questions		20 pts
Conclusion		11 pts

Appendix B : Specific Heat Chart

Appendix C

How to write a conclusion: ¼ page

1.Purpose restated

2. Did you meet the objective(s)? Why or why not?

Refer to graph or data table. State % error as evidence–Lower than 5% is a successful expt.

3. Suggestions to improve the possible errors.

4. Suggestions to enhance the lab.

5. Suggestions to extend the lab.

Name _____________________________________ Lab Section ________Date________________

Pre-laboratory Assignment: Experiment 12

Determination of Specific Heats

All numerical answers should be given to the correct number of significant digits. (Submit your answers on separate sheets as necessary.)

• What is the Law of Dulong and Petit? What are its strengths and what are its limitations?
• What is the definition of specific heat?
• According to the lab manual, why is it a good idea to use a calorimeter constant for the calorimeter? How much error is introduced by not using a calorimeter constant in your calculations for the specific heat?

4. What effect will a 1.0°C error (reading is 1.0°C greater than the actual value) in reading the final temperature have on determining the specific heat of Al? Justify your answer.

5. What effect will a 1.0°C error (reading is 1.0°C greater than the actual value) in reading the final temperature have on determining the specific heat of Cu? Justify your answer.

6. What effect will a 0.10 g error (reading is 0.10 g lower than the actual value) in reading the amount of Al in this calorimetry experiment have on determining the specific heat?

7. What effect will a 0.20 g error (reading is 0.20 g lower than the actual value) in reading the amount of Cu in this calorimetry experiment have on determining the specific heat?

How to produce data using the simulation:

Online Activity: Calorimetry

https://media.pearsoncmg.com/bc/bc_0media_chem/chem_sim/calorimetry/Calor.php

Directions for using the Simulator:

 Click on link above.

 Click on the “Experiment” tab.

 Click on “Run Demonstration” and follow the prompts to learn how to use the simulator. Once

you feel like you understand how the simulator works, go back to the “Experiment” tab and click on “Run Experiment”.

Procedure:

1. Use the simulator to determine the specific heat of copper, aluminum and two unknowns.

2. Open the solid menu under the beaker and select a metal, e.g., copper.

3. Select the mass as 50 grams.

4. Heat the sample to 100 ºC.

5. Select “next” in the column to the left.

6. Open the liquid menu under the calorimeter and select water.

7. Select the mass of the water as 200 grams.

8. The water in the calorimeter is set to 20 ºC.

(Note: When adding metals to water, the water temperature always starts at 20 ºC, you do not need to set this parameter.)

8. Select start.

9. Wait for the equilibrium (final) temperature from the electronic read-out to stabilize and record it.

CALCULATIONS

Note: Use a Scientific calculator for this analysis. Report your calculations to the correct number of significant digits. (Submit your answers on separate sheets as necessary.)

Be sure to record all measurements made, and to show all calculations for determining the specific heat, molar heat capacity and estimated atomic mass of the metal if it applies.

Name ____________________________________ Lab Section _______ Date______________

Report on Experiment 23

Determination of Specific Heats

Data and results
	Aluminum	Copper	Unknown #1	Unknown #2
mass of beaker and sample	NA	NA	NA	NA
mass of beaker	NA	NA	NA	NA
Mass of sample	50g	50g	40g	40g
Initial temperature of sample
Initial temperature of water in calorimeter
Equilibrium (final) temperature of calorimeter
mass of water in the calorimeter
calorimeter constant	NA	NA	NA	NA
specific heat
estimated atomic mass	NA	NA
molar heat capacity
name of metal

REPORT ON EXPERIMENT 23 Determination of Specific Heats

Show details of all calculations; use extra sheets if necessary

Post Lab question:

• Briefly discuss whether the following experimental “mistakes” would have no effect, produce a high result, or produce a low result in the value calculated for the specific heat in your experiments.
  • The mass of aluminum was smaller than reported.
  • If 45 mL of distilled water was used in the calorimeter rather than 30.
  • The actual calorimeter constant is larger than the assumed value.

2. What effect would an uncertainty of 0.50°C in reading all temperatures have on the determination of the specific heat of copper in your experiment?

3. A student measures the heat capacity of a 35.0 g metal sample believed to be pure silver (Cp = 25.5 J mol^-1 deg^-1 . Subsequent analysis indicates that the metal sample is 80% silver and 20% copper. In what way will the observed heat capacity of the metal mixture differ from the value obtained for pure silver? Explain your answer fully and show all calculations used in arriving at an answer.