TEACHER CAUTION: Before performing this activity, be sure that no student who will enter the room or be exposed to the smoke has a peanut allergy.

PART 1- QUESTIONS

QUESTIONS

1. What was the volume of water that was heated by the burning peanut? (accept all reasonable answers)
2. What was the initial temperature of the water? What was the final temperature of the water? How many °C did it rise? (this value is obtained by subtracting the initial water temperature from the final water temperature)
3. Use the following equation to determine the heat gained by the water:
   
   Calories = (mass of water) (change in temperature of water)
   
   For our approximation, we'll equate mLs and grams, therefore: calories = (volume of water) (change in temperature of water)
   
   We'll also simplify our calculations by assuming that minimal heat was lost to the surroundings. Therefore, we'll set the heat gained by the water equal to the heat lost by the peanut.
   
   
4. What was the initial mass of the peanut? What was the final mass of the peanut? What was the mass of the peanut that was burned? (the mass of the peanut burned is obtained by subtracting the final mass of the peanut from its initial mass)
5. To calculate the calories per gram of the peanut, use the following equation:
   
   calories per gram = (heat gained by water)/(mass lost when peanut burned)
   
   
6. To calculate the number of nutritional Calories per gram simply divide the heat calories from question 5 by 1000.

EXTENSIONS

WATER'S MASS
To simplify our calculations, we set the mass of 1 mL equal to 1 gram. How accurate is such an approximation? To find out, use a laboratory balance to obtain the mass of a beaker. Record this value. Use a graduated cylinder to introduce 100 mL of water to this beaker. Determine its new mass. Subtract the initial mass from the final mass to obtain the mass of 100 mL of water. Divide this value by 100 to obtain the mass of 1 mL. Was the approximation you used in the previous experiment acceptable? Explain. (accept all reasonable answers)

LOSING HEAT
The experimental design was flawed. All of the energy released by the burning peanut was not absorbed by the water. Where did it go? (changed into light, absorbed by the test tube glass, lost as heat to the surrounding air) Can you design a better set-up in which less heat energy is lost? Think about it. Then create a set of blueprints for a laboratory tool that would more efficiently transfer heat from a burning material to a quantity of water.

CURRICULUM LINKS

Chemistry:  Chemical Reactions, Heat of Reaction  Biology:  Health, Nutrition

NATIONAL SCIENCE STANDARDS (Grades 5-8)

Science As Inquiry-Content Standard A

Students should develop abilities necessary to do scientific inquiry,

Students should develop an understanding about scientific inquiry

Physical Science -Content Standard B

Students should develop and understanding of the properties and changes  of properties in matter

Students should develop and understanding transformations of energy

Science and Personal and Social Perspectives -Content Standard F

Student should develop an understanding about personal health

Back to Teaching Guide