Heat and Energy

Food Calorimetry


Audience

High school students (10 – 12)


Time frame

Set-up: 5 minutes

Activity: 40 minutes

Clean up: 5 minutes


Standard and educational expectative


Standard: Energy and interactions

     

Expectative: Q.CF1- Matter and their interactions: conversion de la energía y masa

Indicadores: ES.Q.CF1.IE. 4, 14 y 10


Objectives

                   

                   After the activity is completed, students will be capable of:


1. It explains the different types of foods that are capable of generating heat and energy.

2. Analyze the various types of materials by which food are made of.

3. Quantify the amount of chemical energy stored in different types of food (e.i. proteins, carbohydrates, fats).                                                                                                                            

4. It explains the effect of the size of can and relationship of the amount of water in the can.


Vocabulary and Definitions:

  1. Heat

  2. Energy

  3. Temperature

  4. Calorimetry/Thermodynamics

  5. Calorie

  6. Proteins

  7. Carbohydrates

  8. Fats


Scientific Background

Combustion is the process by which a material (usually what is commonly called a fuel) is transformed resulting in the release of heat. The components of food (i.e. proteins, carbohydrates, fats) can be combusted to determine the amount of energy stored within. Energy from food is acquired by the body after food is digested and absorbed.  To obtain this value experimentally a calorimeter is needed.  The basic principle of the calorimeter is to use the energy released by the selected food during combustion to heat water that is contained in a tin can.  The fundamental principle is that energy released as heat by the food is completely absorbed by the water. This is true, as the LAW OF CONSERVATION OF MASS AND ENERGY must be fulfilled. The mathematical relationship used to calculate the amount of heat absorbed by the water is


Qwater = -Qfood


Qwater = mwater Cp (Tf - Ti)


Where


Qwater is the heat absorbed by the water (in calories)

Mwater = is the mass of water in the can (can be calculated using the density of water (1g/mL)


Cp is the heat capacity of water (1cal/g C)


Tf is the final temperature of water


Ti is the initial temperature of water


Example


Say that you used 50 mL of water and that the initial temperature was 23 oC and the final temperature was 25 oC.


Knowing that the density of water is 1g/mL at 25 oC, therefore we have 50g of water.


QW = 50g (1 cal/g oC) (25-23)oC

QW = 100 cal


Remember, that what you see in the food labels is Calorie (the equivalent to kcal, or 1000 cal).  Therefore, if you measure the weight of what you burned (before you burn it) you can calculate the amount of heat generated by any amount of weight of the food and then compare to what the label says.


For example say that the piece of food weighed 50mg.



this represents that you have 2Cal/g.  For a 100g portion then you have 200 Cal.


Materials

  1. Commercial size empty food can.

  2. Small empty food can (~10oz) (An evaporated milk can will do).  

  3. One roll of transparent double tape or spray glue.

  4. 1 bag of cotton balls

  5. 1 box cotton bandage roll

  6. 1 roll duck tape

  7. 1 glass or kabob rod

  8. 1 wine cork

  9. 1 pin

  10. 1 roll double sided tape or spray glue

  11. 1 food thermometer

  12. Balance (a food balance can do)

  13. Graduated cylinder

  14. Matches, lighter

  15. Distilled water



Methods


  1. Take the big commercial food can and remove the top and the bottom side.

  2. Make sure the can is well cleaned.

  3. Take the big commercial food can and make two holes on top.  You can use a drill to do so.

  1. Now, make several holes on the bottom of the can. This is important because it will prevent that when the food catches fire it will not go to completion because of oxygen depletion.

  2. Take the smaller can and also make two holes on top.  You can use a drill to do so.

  3. Use the spray glue or the double sided tape (like the one used for gift wrapping) and spray or taped it around the can.

  4. Take the cotton balls and glue them around the can.  Make sure that you did not cover the holes you already did.

  5. When the whole can is covered (several coats of cotton will do), cover the can with duck tape. The last two steps are important because this will isolate the can and minimize heat losses through the can.  This will allow us to assume that all the heat released is absorbed by the water.

  6. Take the cork and put the pin upside down (the pointy side should be up)

  7. Measure the desired amount of water with the graduated cylinder and pour it in the small can.

  8. Put the glass or kabob rod through the holes of the big and small can in such a way that the small can will be suspended from the big can.

  9. Put the thermometer in the water and record the initial temperature. MAKE SURE THAT THE THERMOMETER IS NOT TOUCHING THE BOTTOM.

  10. Take the food you desire to measure and weight it. Record the weight.

  11. Very carefully put the food piece on the pin.  DO NOT USE GLUE OR ANY OTHER MATERIAL TO FIX THE FOOD.

  12. With a lighter or a match start the process of combustion in the food.

  13. Immediately put the big/small can arrangement on top of the cork with the pin and the food.  See Figure 1 for reference.

  14. Allow combustion to go to completion. You will know it was completed because smoke will start to rise and you will not see any more flames.

  15. Look at the thermometer and observe how the temperature starts to rise.  Observe the thermometer continuously and record the highest temperature that was achieved. This will be your final temperature.

  16. Repeat the process with various pieces of the same food.  This will allow you to corroborate your measurements.

  17. Now you have all the data to do your calculations.  You can repeat the process for different foods or types of vials.



Figure 1.  Calorimeter arrangement.


Troubleshooting


-Calculations are not in accordance with what the label says


The analysis assumes that “all” the heat evolved is “absorbed” by the water.  Therefore, heat losses need to be minimized by:

  • insulating your outer can (see above in methods)

  • use a small metal can inside (don’t use a beaker)

  • using distilled water (the heat capacity of water was assumed and therefore any impurity from faucet water will affect measurement). The ideal would be to use deionized water


Make sure that the food was completely consumed.  It is OK that at the end you have a black residue.  The important thing is that you visually don’t see any unburned parts.  If this happens start again with a new piece.  Maybe try one that is smaller.


If you get an overestimate it is possible that the thermometer was touching the metal at the base of the can. This will potentially cause an overestimation of the temperature reached by the water.


-Food does not catch fire


It is normal that some foods will catch fire more easily than others. However, make sure that all the food that you use is dry. Humidity can make combustion difficult.  There are some foods that are fairly convenient to use.  Some suggestions are:

  • Cheese puffs

  • Cheetos

  • Corn pops

  • Nuts


-Food catches fire but it turns off quickly after you put the can on top.


The reason most likely is that oxygen is consumed and the flame is deprived of it.  Make sure that the can is not flat on the counter and that the smaller can is not too big.  This is the reason why the can should have holes on the bottom.


Questions


  • What are the basic chemical structures of fats, sugars and proteins?

  • Do these types of molecules differ in the amount of energy they contain?

  • If for the small can we use a beaker or a ceramic vial, do you think you will get similar results?

  • If you burn the same food but using different amounts of water, do you expect that the final result be the same?


Additional Resources:

  • http://www.watchknow.org/Video.aspx?VideoID=17223

  • http://www.chemistryexplained.com/Ge-Hy/Heat.html

  • http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/spht.html


Extensions:

Student Research

Students may want to connect this experiment to the real world by further experimentation or research related to foods and their caloric content; the need for high caloric foods for athletes and developing children versus adults; materials for vehicles, including materials used in engines, motors, etc. to dissipate heat; space shuttle tiles, and so on. Students may want to produce a product of their research results, such as a traditional research paper, a review of relevant research, a PowerPoint presentation, or find appropriate videos or make their own videos.


References:


C. Brosnan, Revised by L. Padwa, C. Gorman, L. Giloni, E. Kannengieser Edited by Linda Padwa and David Hanson, (2006). Calorimetry – Measurement of Heat Energy. Stony Brook University


Atkins, P., de Paula, J. (1978/2010). Physical Chemistry, (first edition 1978), ninth edition 2010, Oxford University Press, Oxford UK.


Kondepudi, D. (2008), Introduction to Modern Thermodynamics, Chichester UK: Wiley, Lebon, G., Jou, D., Casas-Vázquez, J. (2008). Understanding Non-equilibrium Thermodynamics: Foundations, Applications, Frontiers, Springer-Verlag, Berlin.


Sizer, F and Whitney, E. 1997. Nutrition Concepts and Controversies. 7th ed. Wadsworth: CA.


                Electronic refrences:


Calorimetry-Water equivalent Calorimetry : vlab.amrita.edu/?sub=2&brch=190&sim...1 Theoryvlab.amrita.edu/?sub=2&brch=190&sim...


Student Worksheet for Heat Energy: Food Calorimetry



Experiment Title: ________________________________ Date: ________ Name: ____________________


Develop a guiding question or questions for your experiment:

Materials: ___________________________________________________________________________

Procedure:  

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Questions:


  1. What are the basic chemical structures of fats, sugars and proteins?








  1. Do these types of molecules differ in the amount of energy they contain?






  1. If for the small can we use a beaker or a ceramic vial, do you think you will get similar results?




  1. If you burn the same food but using different amounts of water, do you expect that the final result be the same?




  1. Analyzes the label below which gives a simple explanation of the same using the information the concepts learned in the laboratory.


http://www.fultonmassagetherapy.com/wp-content/uploads/2014/09/readfoodlabel.jpg


Conclusion (use the back if necessary):