Measurement of Food Energy

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Measurement of Food Energy Name _______________________ Lab Partner: ______________________ Period _______ Date ___________ Purpose : To measure the amount of heat energy released when a nut is burned. Procedure : Find the mass of a peanut and record it on the data table. Place the nut on the end of a pin that is inserted in the cork.

Place exactly 10 ml (one ml of water has a mass of one gram) of water into the test tube. Record the starting temperature of the water on your data table. Attach the test tube to the ring stand with the clamp so that the cork- nut assembly will be about 1cm below the test tube.

Ignite the nut with a match. CAUTION : Use extreme caution with lighted matches . Be sure the nut is not below the test tube when you light the nut.

After the nut is burning, immediately place the cork-nut assembly beneath the test tube. Make sure the test tube is directly over the burning sample. CAUTION : The test tube will absorb heat.

Do not touch the test tube with your fingers. Unscrew the clamp from the ring stand to move the test tube . If complete burning does not ... more. less.

occur, re-light the nut. When burning is complete, immediately measure the temperature of the water in the test tube. Record this final water temperature on your data table. Repeat the procedure using another sample of the same kind of nut. Make sure that you change the water between each trial. Duplicate the procedure with a piece of walnut and popcorn. Using the information in the calculations below, calculate the number of calories in each sample of nut. Enter the number of calories and the mass of each nut in the computer. After the computer calculates the calories per gram, record that information in your data table. Calculate the average calories per gram for each nut and record it on the data table. Compare your results with those of your classmates. After the computer calculates the class averages for each type of nut, record this information on your data table. Data : Sample & Trial Mass of Sample Mass of Water Initial H 2 O Temperature Final H 2 O Temperature Temperature Change Calories Calories/g Average Calories/g Class Ave. Calories/g Peanut a Peanut b Walnut a Walnut b Popcorn a Popcorn b Measurement of Food Energy 2 Calculations : Calories = mass of water X temp. change Peanut a Calories = Peanut b Calories = Walnut a Calories = Walnut b Calories = Popcorn a Calories = Popcorn b Calories = Conclusion : 1. What is the relationship of a calorie to the chemical energy stored in foods? ____________________________ _________________________________________________________________________________________ 2. Grizzly bears are known to eat the fatty parts of many animals. What property of fatty tissues makes them a good food source for bears?___________________________________________________________________ _________________________________________________________________________________________ 3. How does your data compare to the rest of the class? _____________________________________________ _________________________________________________________________________________________ 4. Using the class data, explain which nut has the most potential chemical energy. _________________________ _________________________________________________________________________________________ 5. Explain how energy was transformed as the nut was burned. ______________________________________ _________________________________________________________________________________________ _________________________________________________________________________________________ 6. What provided the activation energy that started each nut burning? ___________________________________

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