Chemistry 30

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Purpose

• To graph the data for the cooling of water.
• To calculate rate of cooling
• To compare rates of cooling for different time periods.

Equipment and Materials

• thermometer
• heat source – Bunsen burner or hot plate
• large beaker or other container for the water
• approximately 500 mL of water

Procedure

1. Heat the water until it begins to boil, then carefully remove it from the heat source.
2. Record the water temperature every 30 s as it cools. Continue recording until the water temperature reaches room temperature or slightly above room temperature

Results

Prepare a graph that shows the results of the data. The graph should be a plot of Temperature (° C) versus Time (min). Students are strongly encouraged to use the graphing capabilities of a spreadsheet such as Excel or Quatro Pro to create the graph. Computer generated graphs are preferable to hand-drawn graphs.

The following items apply to creating graphs:

• All graphs require an appropriate, descriptive title. The name of the substance used in the experiment should be included in the title. Please include your name on all graphs.
• Both axes must be labeled, including the units of measurement ( ° C and min)
• Graphs should fill the page, except for 1 inch margins on all sides.

Conclusions and Questions

1. Calculate the rate of cooling for three time periods:

• the entire cooling period
• the first ten minutes
• the last ten minutes

2. How do these values compare?