A scientist is attempting to determine the caloric value of a food item by condu

Question

A scientist is attempting to determine the caloric value of a food item by conducting food calorimetry. In the process of burning the food item, a significant amount of heat energy is lost and not transferred to the water that is being monitored for temperature change. This would lead to which of the following kinds of results? A) The calculated calories per gram would appear higher than in reality B) The calculated calories per gram would appear lower than in reality C) The percent energy coming from lipids would appear higher than in reality D) The percent energy coming from carbohydrates would appear higher than in reality E) The percent energy coming from protein would appear lower than in reality

Explanation / Answer

This experiment employs a technique called calorimetry. The heat energy from the combustion of the food will be transferred to a measured quantity of water. By measuring the temperature change of the water, you will be able to determine how much energy was released per gram of food burned. It is well documented that in order to make the temperature of one gram of water rise by 1 Co, one calorie of heat must be absorbed. This quantity of energy is called a calorie. You will determine how many calories of heat are given off per gram of food reacted. Before beginning the experiment, you are expected to develop a hypothesis based on what you have learned in this unit. Using your knowledge of the types and number of bonds found in sugars, fats, and carbohydrates, make a prediction as to which food group has the highest and lowest calorie content. You may refer to food labels or conduct an internet search.The hypothesis is an educated guess, and you must be able to justify it with background information. Be sure to clearly state your results in the conclusion.

Was the hypothesis valid? What could be done to improve the experiment?

In the discussion, list five things you learned about chemical reactions as a result of this investigation. You and your partner will submit a typed lab report. The attached rubric indicates how the lab report will be scored. The report is worth 100 points.

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