Evaluation copy. Energy Content of Fuels. computer OBJECTIVES MATERIALS

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1 Energy Content of Fuels Computer 9 Energy content is an important property of fuels. This property helps scientists and engineers determine the usefulness of a fuel. Energy content is the amount of heat produced by the burning of 1 gram of a substance, and is measured in joules per gram (J/g). You can determine energy content of a fuel by burning an amount of the fuel and capturing the heat released in a known mass of water in a calorimeter. If you measure the initial and final temperatures, the energy released can be calculated using the equation H = t m C p where H = heat energy absorbed (in J), t = change in temperature (in C), m = mass (in g), and C p = specific heat capacity (4.18 J/g C for water). Dividing the resulting energy value by grams of food burned gives the energy content (in J/g). OBJECTIVES In this experiment, you will Use a computer to measure temperature. Use a computer to analyze data. Use a balance. Determine energy content. Compare the energy content of different fuels. MATERIALS computer Vernier computer interface Logger Pro Vernier Temperature Probe fuel sample (candle, oil, or alcohol) ring stand and 10 cm (4") ring utility clamp slit stopper 100 ml graduated cylinder 2 stirring rods balance small can cold water matches Evaluation copy Figure 1 Physical Science with Vernier 9-1

2 Computer 9 PROCEDURE 1. Obtain and wear goggles. 2. Connect the probe to the computer interface. Prepare the computer for data collection by opening the file 09 Energy of Fuels from the Physical Science w Vernier folder. 3. Find and record the initial mass of the lamp with fuel sample or candle assigned to you. Make sure no more than 0.5 cm of wick sticks out of a lamp. 4. Set up the apparatus shown in Figure 1. a. Determine and record the mass of the empty can. b. Place cold water from the teacher into the can. Use 100 ml for candles and 200 ml for alcohol and oil. c. Determine and record the mass of the can plus water. d. Use a 10 cm ring and stirring rod to suspend the can about 5 cm above the candle or lamp. e. Use a utility clamp and slit stopper to suspend the Temperature Probe in the water. The probe should not touch the bottom of the can. 5. Click to begin measuring temperature. Remember: The Temperature Probe must be in the water for at least 45 seconds before you begin! After 3 or 4 temperature readings have been made, light the lamp or candle. Record the initial temperature. Heat the water until its temperature reaches 40 C and then extinguish the flame. CAUTION: Keep hair and clothing away from open flames. 6. Stir the water until the temperature stops rising. Record this final temperature. Click to end data collection. 7. Determine the final mass of the lamp and fuel or candle. 8. To confirm the initial temperature, examine the initial data points in the table. To confirm the final temperature, click the on the graph to select it and then click the Statistics button,. The maximum temperature is listed in the statistics box on the graph. 9. Repeat the procedure using a different fuel. Start with cold water again. 9-2 Physical Science with Vernier

3 DATA Trial 1 Trial 2 Fuel used Mass of lamp and fuel or candle (initial) g g Mass of lamp and fuel or candle (final) g g Mass of empty can g g Mass of can plus water g g Energy Content of Fuels Initial water temperature C C Final water temperature C C PROCESSING THE DATA 1. Calculate the change in water temperature, t, for each sample by subtracting the initial temperature from the final temperature ( t = t final t initial ). 2. Calculate the mass (in g) of the water heated for each sample. Subtract the mass of the empty can from the mass of the can plus water. 3. Use the results of Steps 1 and 2 to determine the heat energy gained by the water (in J). Use the equation H = t m C p where H = heat absorbed (in J), t = change in temperature (in C), m = mass of the water heated (in g), and C p = specific heat capacity (4.18 J/g C for water). 4. Calculate the mass (in g) of fuel burned. Subtract the final mass from the initial mass. Physical Science with Vernier 9-3

4 Computer 9 5. Use the results of Steps 3 and 4 to calculate the energy content (in J/g) of the fuel samples. 6. Record your results and the results of other groups in the Class Results Table below. Class Results Fuel Type Fuel Type Fuel Type Fuel Type Avg. 7. Which of the fuels has the greatest energy content? 8. List two other factors, in addition to energy content, that might be important in choosing a fuel. EXTENSIONS 1. Make a bar graph comparing the fuels tested in your class. 2. Design an experiment to compare heat content of different alcohols or oils. 9-4 Physical Science with Vernier

5 Vernier Lab Safety Instructions Disclaimer THIS IS AN EVALUATION COPY OF THE VERNIER STUDENT LAB. This copy does not include: Safety information Essential instructor background information Directions for preparing solutions Important tips for successfully doing these labs The complete Physical Science with Vernier lab manual includes 40 labs and essential teacher information. The full lab book is available for purchase at: Vernier Software & Technology S.W. Millikan Way Beaverton, OR Toll Free (888) (503) FAX (503)