1. Energy: Matter in Motion
Chapter 5
Remind Ms J to clock in
Energy: Matter in Motion

2. Energy: the ability to do work Why do food scientists care?
They examine how heat is transferred during cooking and preservation and how energy affects the structure of food during such processes
This helps develop new food products to meet the needs of consumers

3. Potential and Kinetic Energy
Potential energy:
is stored energy. In food it is in the form of chemical potential energy called calories
Food contains internal potential energy
kinetic energy:
energy of motion. The faster an object moves, the more kinetic energy it has
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4. Forms of Energy All forms of energy are used by the food industry:
Mechanical (potential plus kinetic)
chemical
electrical
nuclear
Radiant
Energy can change from one form to another
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5. Forms of Energy and Food
Mixers, blenders, and food processors convert electrical energy to mechanical energy that performs work on food
Metabolism allows the body to utilize chemical energy from food when bonds between atoms that make food are broken
Electrical energy is converted into mechanical or radiant energy for food processing

6. Forms of Energy and Food
cooking appliances and outdoor grills use radiant energy to cook food
Microwave ovens convert electrical energy to radiant energy (low-frequency electromagnetic waves called microwaves)
Nuclear energy is used in food preservation such as irradiation
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7. Measuring Energy Heat:
is an energy transfer from one body to another caused by a temperature difference between the 2 bodies
Food energy is measured in terms of the capacity to produce heat
calorie:
heat needed to raise the temperature of one gram of water one degree Celsius
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8. Measuring Energy
Heat capacity: ability of a substance to absorb heat (high water content, high capacity) Specific heat: amount of energy needed to raise the temperature of 1 g of a substance 1° Celsius Temperature: measure of the average kinetic energy of molecules Very important to ensure food safety and product quality
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9. How Heat is Transferred
Heat flows from hot objects to cooler ones
Thermodynamics studies heat flow and temperature in relation to material properties
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10. Conduction:
the transfer of heat through matter from particle to particle collisions
Occurs only in metals at the molecular level
Heated electrons skip over tens or hundreds of atoms and speed the heat transfer
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11. Convection:
is the transfer of heat by the motion of molecules in fluids, such as water or air
As the temperature increases, convection currents are generated that speed heating
It is faster than conduction
Ex. cooking food in water
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12. Radiation the transfer of heat by electromagnetic waves
It does not need the presence of matter
Ex. broiling and rotisserie cooking
causes most of the browning of baked and roasted foods
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13. Energy Flow in Phase Changes
Phase changes need a flow of energy
Fusion/melting:
solid to liquid phase
Crystallization/freezing:
liquid to solid phase is called freezing
latent heat of fusion:
energy needed to melt or freeze a substance
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14. Energy Flow in Phase Changes
Evaporation/vaporization
liquid to gaseous phase
Condensation/liquefaction
gas to a liquid phase
latent heat of vaporization
energy needed to evaporate or condense a substance is the
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15. Energy Flow in Phase Changes
Deposition
gas phase to a solid phase
sublimation
solid phase to a gas phase
At the point of a phase change, the temperature remains constant
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16. Factors That Affect Rates of Reaction in Food Preparation
Temperature of reactants
The rate of a reaction approximately doubles for every 10°C increase in temperature
Amount of surface area
The greater the surface area, the faster the reaction is
Thickness of the food
The thicker the food, the longer it will take to cook