Heating and Cooling Curve of Paradichlorobenzene

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once the test tube of PDB is placed into the bath and keep the bath at

a constant 65oC by moving the beaker on and off the hot plate as necessary.

3. When ready, begin recording data.

4. Quickly place the test tube of PDB into the hot water bath.

5. Record until the temperature has reached about 60oC.

6. Email the data to your lab group.

Clean Up

1. When finished, removed any PDB from the probe by placing in hot water bath and wiping with a paper towel.

2. Empty beakers, turn off hot plate, and clean lab station.

3. Return temperature probe and Go Wireless interface.



Analysis Questions:

1. Determine the freezing point and melting point of PDB from your graph. Explain how you have concluded this.

2. How should the melting and freezing points compare? Explain? (2)

3. How would an increase in the amount of PDB affect the general shape of the graph? Would the plateau

change? Explain. (1)

4. If the heat of fusion for PDB was higher, how would your cooling curve change? Explain. (2)

5. If the specific heat of PDB was lower, how would your cooling curve change? Explain. (2)

6. In the procedure, you were instructed to monitor the temperature of the cold and hot water baths during the cooling and heating of the PDB sample. Why is this important? What would occur if this was not done.

7. During the cooling process, heat is continually being removed from the PDB. Describe what is happening to the movement and spacing of the molecules at each of the following three stages of your cooling graph. Include how this affects the kinetic and potential energy of the system. You should mention what occurs in terms of molecular motion and intermolecular forces. (6)

a. at the start when the temperature decreases rapidly

b. when the temperature reaches a plateau (temp barely changes)

c. at the end when the temperature begins decreasing again