Report Heat Relationships in Physical and Chemical Processes

Test all eight of the compounds using the same mass value for each. Some of your compounds may cause an increase in temperature of the solution, other compounds could cause a decrease in the temperature of the solution.

Write a specific question that you can answer as a result of performing your calorimetry experiment.

Part I A. Design and carry out an experiment to determine the change in enthalpy, H (kJ), for the dissolving process for the nine ionic solids.

1. Write the chemical formulas for all eight ionic solids.
Ionic Solid Chemical Formula
Ammonium nitrate
Sodium nitrate
Calcium nitrate
Magnesium nitrate
Sodium chloride
Calcium chloride
Lithium chloride
Magnesium chloride
Ammonium chloride

2. In your experiment, identify the independent and dependent variables.

3. What is the magnitude and unit of the control variable in your experiment?

4. Write equations that describe the dissolving process for each salt. Classify each process as endothermic, exothermic, or neither after collecting the data.
Ionic Solid Chemical Equation Type Energy Change
Ammonium nitrate
Sodium nitrate
Calcium nitrate
Magnesium nitrate
Sodium chloride
Calcium chloride
Lithium chloride
Magnesium chloride
Ammonium chloride

5. List the assumptions and or information that you need to make in order to do the calculations.

6. In your experiment, identify the system.

7. In your experiment identify the surroundings.

8. In your experiment, what gains heat energy?

9. In your experiment what loses heat energy?

10. Report the heat of reaction (qRxn) for each ionic solid. Show your calculation or each salt. Report the final value in Joules.

Ionic Solid Calculation qRxn (J)
Ammonium nitrate
Sodium nitrate
Calcium nitrate
Magnesium nitrate
Sodium chloride
Calcium chloride
Lithium chloride
Magnesium chloride
Ammonium chloride

11. Calculate the H, change in enthalpy per mole of salt, and report the value in units of kJ/mol. Show your calculation for each salt. Remember that qRXN is the heat energy for the mass of salt dissolved in the experiment.
Ionic Solid Calculation H Rxn (kJ/mol)
Ammonium nitrate
Sodium nitrate
Calcium nitrate
Magnesium nitrate
Sodium chloride
Calcium chloride
Lithium chloride
Magnesium chloride
Ammonium chloride

12. Describe any patterns of observed in H for the nitrate salts and the chloride salts. Is there a periodic trend in H for the Group I chloride salts? Is there a periodic trend in H for the Group II chloride salts? Are the trends the same?

Part II Relationships in Enthalpy Changes

Design and carry out a series of experiments that investigates ONE of the following questions: 1) whether the mass of an ionic solid dissolved in a given volume of water has any effect on how much the temperature of the solution will change, OR 2) whether the mass of the water used when dissolving a constant mass of an ionic solid has any effect on the temperature change. You will collect at least six trials of data and make a graph that illustrates the relationship between the variables that were chosen to study.

13. In your experiment, identify the independent, dependent and control variables.

14. Write a specific question that you can answer as a result of performing your experiment.

15. Predict the relationship between the independent and dependent variable before you collect data. Briefly explain your prediction.

16. List the assumptions and or information that you need to make in order to do the calculations.

17. Make a data table summarizing the magnitude and units of your independent and dependent variables. Add additional columns and rows, if needed. Edit the variable names of any of the columns in the table below. Show all of your calculations.
Ionic Solid Calculation T Rxn (oC)

18. Construct a graph of the data from your experiment in Excel. Don’t forget to include all of the required parts of a scientific graph. Paste your graph below.

19. What is the relationship between the variables in your experiment based on the graph?

20. Do the results agree with your prediction? Why or why not?

Overall Analysis Questions
21. Is dissolving an ionic salt in water a chemical or physical process? Explain.

22. Does doubling the amount of substance that dissolves in water correspond to a doubling of a temperature change in the solution?

23. What is the difference between the heat of reaction, qrxn, and the enthalpy of reaction, HRxn?

24. Can you make a prediction about which ionic compounds will cause an increase or decrease in the temperature of the solution when they dissolve in water?

25. What causes the changes in temperature that you observed to occur (how does it happen)? Draw a diagram at the molecular level that illustrates what is happening. In each case, identify the system and surrounding.

Part III Determine the Specific Heat of Metals

26. Determine the average specific heat capacity, c, of copper from the group data in Part III. Use the equation for the total heat flow, qmetal + qwater = 0 (show your work for one sample, provide values for four other samples). Compare your experimental values to the published value for copper (0.398 J/goC)

Trial Mass of Copper (g) Specific heat capacity (J/gºC)
1
2
3
4
Average Four Samples
Average All Group Data Samples:

27. Determine the average specific heat capacity, c, for each unknown metal using the equation for the total heat flow, qmetal + qwater = 0 (show your work for one sample, provide values for four other samples). Identify each metal from the following list:
(Al, c = 0.897 J/gºC; Ni, c = 0.54 J/gºC; Zn, c = 0.388 J/gºC; Sn, c= 0.228 J/gºC;
Pb, c = 0.129 J/gºC).

Sample Calculation:

Trial Mass of Metal A (g) Specific heat capacity (J/gºC)
1
2
3
4
Average Four Samples

Average All Group Data Samples: Metal A:

Sample Calculation:

Trial Mass of Metal B (g) Specific heat capacity (J/gºC)
1
2
3
4
Average Four Samples

Average All Group Data Samples: Metal B:

Expand Your Thinking

28. Indicate whether the average of all group data values for the specific heat of copper is less than, equal to or less than the literature value of specific hear for copper.

Average Ccopper 0.398 J/goC

29. Consider the procedures, uncertainty of all measurements and other extenuating circumstances in the determination of the experimental value of the specific heat of copper. What are sources of error that lead to the relationship between the average group data value and the literature value?

30. Indicate whether the average of all group data values for the specific heat of Metal A is less than, equal to or less than the literature value of specific hear for Metal A.

Average CMetal A J/goC

31. Consider the procedures, uncertainty of all measurements and other extenuating circumstances in the determination of the experimental value of the specific heat of Metal A. What are sources of error that lead to the relationship between the average group data value and the literature value? How certain are you about the identity of the metal?

32. Indicate whether the average of all group data values for the specific heat of Metal B is less than, equal to or less than the literature value of specific hear for Metal B.

Average CMetal B J/goC

33. Consider the procedures, uncertainty of all measurements and other extenuating circumstances in the determination of the experimental value of the specific heat of Metal B. What are sources of error that lead to the relationship between the average group data value and the literature value? How certain are you about the identify of the metal?