Food, Fuel and Energy

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Food, Fuel and Energy

• Chemistry 100
• Fall 2003

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ENERGY

• Energy
• The capacity to do work
• Potential Energy
• Energy stored in an object or a substance
• Kinetic Energy
• Energy of motion

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Doing work generates heat
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Sir Frances Bacon

• Sir Bacon stated that heat is the consequence of
  motion and nothing else
• Discovered the benefits of refrigeration

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Heat results from the brisk agitation of the
particles of matter
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Count Rumford

• Bored cannons
• Developed the caloric theory
• calorie (cal) is the amount of heat (or energy)
  needed to raise the temperature of one gram of
  water by one degree Celsius.
• A kilocalorie (kcal) is equal to 1000 cal
• Called a nutritionists calorie 1 Cal

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Calorimetry

• Technique of measuring the amount of heat that is
  equivalent to a specific amount of energy or work
• Device used is called a calorimeter

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Calorimetry

• Suppose you heat 0.5 kg of water for a short time
  and the temperature raises 3 oC. How many
  calories did you add to the water?
• 0.5 kg 500 g
• 1 cal is needed to raise 1 g - 1 oC
• therefore you needed to add 500 cal for 1 oC
• Since is went up 3 oC you added 1500 cal

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Joule

• Joule J
• Is the work done by one watt of electricity in
  one second
• 1 J 0.24 cal 1 cal 4.2 J

James Prescott Joule
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Joule

• How many kilocalories of energy does it take to
  keep a 100-watt light bulb lit for 1 minute?
• 1 J 1 watt-sec
• 100 watts x 60 sec 6000 watts-sec 6000 J
• 6000 J x 1 cal/4.2 J x 1 kcal/1000 cal
• 1.4 kcal

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• Exothermic Reaction
• A reaction that releases energy to the
  environment
• Combustion reactions
• Endothermic Reaction
• A reaction that absorbs energy from the
  environment
• Ice melting

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Metabolism

• Metabolism encompasses all the chemical reactions
  that take place in any living organism, including
  those that release the chemical potential of our
  foods

Energy In Energy Out Energy Stored
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Energy Out

• The human body uses energy in three ways
• Exercise
• Specific Dynamic Action
• Basal Metabolism

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Exercise

• The physical work our bodies do
• Level Example Cal/min
• Very light Sitting 1.0 2.5
• Light Shopping 2.5 5.0
• Moderate Dancing 5.0 7.5
• Heavy Running 7.5 12.0

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Specific Dynamic Action

• SDA the energy consumed in digesting and
  metabolizing food and converting its energy into
  our own that the body can utilize

The price we pay for extracting energy from food
for fat it is about 4 of the energy content of
the food for carbohydrates it is about 6 and
for proteins it is 30. In general it is about
10 of the total
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Basal metabolism

• Is the energy we use to keep our heart beating,
  our lungs expanding and contracting and our other
  organs working to maintain life
• About 1 Cal per hour per kg of body weight
• Increases with any body stress

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Energy in Macronutrients

• Fats
• 9 Cal/g
• Carbohydrates
• 4 Cal/g
• Protein
• 4 Cal/g
• Ethyl alcohol
• 7 Cal/g

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Calories in food

• A meal contains 10 g of fat, 15 g of
  carbohydrates and 20 g of protein
• 10 g x 9 Cal/g 90 Cal
• 15 g x 4 Cal/g 60 Cal
• 20 g x 4 Cal/g 80 Cal
• Total 230 Cal

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