Goal. To determine the specific heat of an unknown metal using a coffee cup calorimeter.. Background - Calorimetry. Atmospheric pressure is constant DH = qp qsystem = -qsurroundingsThe surroundings are composed of the water in the calorimeter and the calorimeter. qsystem = - (qwater
1. Experiment 9 Specific Heat Capacity of a Metal
2. Goal To determine the specific heat of an unknown metal using a coffee cup calorimeter.
3. Background - Calorimetry Atmospheric pressure is constant DH = qp qsystem = -qsurroundings
The surroundings are composed of the water in the calorimeter and the calorimeter. qsystem = - (qwater + qcalorimeter)
For most calculations, the qcalorimeter can be ignored. qsystem = - qwater csystemmsystem DTsystem = - cwatermwater DTwater
4. Background - Calorimetry csystemmsystem DTsystem = - csurroundsmsurrounds DTsurrounds
c = specific heat
m = mass
DT = change in temperature (Tf – Ti)
5. Background - Calorimetry cmetalmmetal DTmetal = - cwatermwater DTwater
6. Background - Calorimetry cmetalmmetal DTmetal = - cwatermwater DTwater
7. Background - Calorimetry cmetalmmetal DTmetal = - cwatermwater DTwater
8. Background - Calorimetry An equation derived by Dulong and Petit can be used to estimate the atomic weight of a metal from the substance’s specific heat.
9. Experimental Procedure There are four main procedures to this experiment
Set-up the calorimeter
Boil the water containing metal
Set-up the GLX computer.
Collect the calorimetric data.
10. Background - Calorimeter
13. Calorimetric Set-Up
14. Experimental Procedure – Collecting Data Weigh out approx. 20 grams of unknown metal, place it in a test tube and warm in a hot water bath.
Weigh the calorimeter, add approximately 20 mL of water and reweigh the calorimeter and water.
After the metal has been in the hot water 5 minutes, start the experiment by pressing “Record” on the GLX and start swirling the liquid in the calorimeter.
After one minute, add the hot metal and continue swirling.
Discard the water, place the metal in the wet metal beaker, and repeat the experiment.
15. Experimental Procedure – Data Analysis
16. Experimental Procedure – Data Analysis
17. Experimental Procedure – Data Analysis
18. Calculation – Specific Heat
19. Calculation – Specific Heat
20. Calculation – Molecular Weight Estimate.
21. Calculation – Molecular Weight Estimate.
22. Safety Be careful handing hot glassware and metal as they can be hot.
Be sure to keep computers and calorimeters away from the hot plates, both can melt when exposed to heat.
23. Waste Disposal Put all metal into containers marked: “Wet Unknown”
24. Quiz Name, Lab day and time