Specific Heat of a Metal Lab

Specific Heat of a Metal

Objective: To identify the specific heat of a metal and compare to the actual specific heat to our calculations.  Then to use this technique to identify an unknown metal.

Pre-Lab Questions:

1. Why do we measure the water’s volume in milliliters instead of in grams since the specific heat is in measured in J/g∙°C?

2. A 22.50 g piece of an unknown metal is heated to boiling (100°C) then transferred quickly and without cooling into 100 mL of water at 20.0°C. The final temperature of the system is 26.9°C.

a. Calculate the quantity of the heat absorbed by the water. Show all work.

b. Determine the quantity of heat lost by the piece of metal.

c. Calculate the specific heat of the metal in J/g∙°C. Show all work.

Procedure:

1.      Heat 200 mL of water to boiling. It must be rapidly boiling, if unsure ask Ms. Cotta.

2.      Meanwhile measure a sample of metal on the balance and record the mass and identity in your data.

3.      Measure 100 mL of water and place in your Styrofoam cup, record the volume and mass in your data.

4.      Record the initial temperature of the water in your data.

5.      When the water is boiling, carefully place your metal into the boiling water and leave for three minutes.

6.      After three minutes, carefully pull your metal out of the boiling water using a tool and immediately place in your prepared Styrofoam cup of water.

7.      Determine the highest temperature that the water reaches and record in your data. (MAKE SURE THERMOMETER IS TOUCHING WATER AND NOT METAL!)

8.      Make sure all the data is collected and written down.

Data for three trials:

Identity of metal:                              _________                _________                _______

Mass of metal sample:                    _____ g                      ______ g                    _____g

Volume of water used:                    _____ mL                   ______ mL                 _____mL

Mass of water used:                         _____ g                      ______ g                    _____g

Initial temperature of water:          _____ °C                    ______ °C                  _____°C

Final temperature of water:           _____ °C                    ______ °C                  _____°C

Temperature difference:                 _____ °C                    ______ °C                  _____°C

Initial temperature of metal:          _____ °C                    ______ °C                  _____°C

Final temperature of metal:           _____ °C                    ______ °C                  _____°C

Temperature difference:                 _____ °C                    ______ °C                  _____°C

Analysis:

1. Calculate the quantity of heat gained by the water like you did in your pre-lab questions for all three of your trials.

Sample 1: Q = ______J

Sample 2: Q = ______J

Sample 3: Q = ______J

2. Assume that the quantity of heat lost by the metal is equal to the quantity of the heat gained by the water. Use this quantity to determine the specific heat, s, of the metal. Use your DT for the metal from your data. 

Sample 1: _______ J/ g∙°C

Sample 2: _______ J/ g∙°C

Sample 3: _______ J/ g∙°C

3. In your calculations you assumed that all the heat from the metal went into the water. Is this a fair assumption to make? Why or why not?

4. Look at the specific heat of your metal from the white board and calculate your percent error using this equation.

% error = (actual specific heat value) – (your specific heat value calculated)        x 100%

                                                            (actual specific heat value)