Beyond Labz Specific Heat of Metal 3-4: Specific Heat of Pb

On a sunny day, the water in a swimming pool may warm up a degree or two while the concrete around the pool may become too hot to walk on with bare feet. This may seem strange since the water and concrete are being heated by the same source—the sun. This evidence suggests that it takes more heat to raise the temperature of some substances than others, which is true. The amount of heat required to raise the temperature of 1 g of a substance by 1 degree is called the specific heat capacity or specific heat of that substance. Water, for instance, has a specific heat of 4.18 J/Kg. This value is high in comparison with the specific heats for other materials, such as concrete or metals. In this experiment, you will use a simple calorimeter and your knowledge of the specific heat of water to measure the specific heat of lead (Pb).

1. Start Virtual ChemLab, select Thermodynamics, and then select Specific Heat of Pb from the list of assignments. The lab will open in the Calorimetry laboratory.

1. Click on the Lab Book to open it. Record the mass of Pb on the balance. If it is too small to read click on the Balance area to zoom in, record the mass of Pb in the data table below, and return to the laboratory.

1. Pick up the Pb sample from the balance pan and place the sample in the oven. Click the oven door to close. The oven is set to heat to 200C.

1. The calorimeter has been filled with 100 mL water. The density of water at 25C is 0.998 g/mL. Use the density of the water to determine the mass of water from the volume and record the volume and mass in the data table.

Make certain the stirrer is On (you should be able to see the shaft rotating). In the thermometer window, click Save to begin recording data. Allow 20-30 seconds to obtain a baseline temperature of the water. You can observe the temperature in the calorimeter as a function of time using the graph window.

1. Click on the Oven to open it. Drag the hot Pb sample from the oven until it snaps into place above the calorimeter and drop it in. Click the thermometer and graph windows to bring them to the front and observe the change in temperature in the graph window until it reaches a constant value and then wait an additional 20-30 seconds. Click Stop in the temperature window. (You can click on the clock on the wall labeled Accelerate to accelerate the time in the laboratory.) A data link icon will appear in the lab book. Click the data link icon and record the temperature before adding the Pb and the highest temperature after adding the Pb in the data table. (Remember that the water will begin to cool down after reaching the equilibrium temperature.)

Data Table

 Pb mass of metal (g) volume of water (mL) mass of water (g) initial temperature of water (C) initial temperature of metal (C) max temp of water + metal (C) 1. Calculate the changes in temperature of the water (Twater).

1. Calculate the heat (q), in J, gained by the water using the following equation:

qwater mwater Twater Cwater , given Cwater= 4.184 J/(Kg)

8

.

Calculate the changes in temperature of the Pb (

T

Pb

).

1. Remembering that the heat gained by the water is equal to the heat lost by the metal, calculate the specific heat of lead in J/Kg.

qmetal qwater qmetal mPb TPb CPb and CPb

(mmetal)(Tmetal)

1. Calculate the percent error in the specific heat value that you determined experimentally. The accepted value for Pb is 0.130 J/ Kg.

% Error 100

% Error =