Chapter 5: Energy: Matter in Motion

Question 1

Define energy.

Answer 1

The ability to do work.

Question 2

What are 2 things that food scientists examine relating to energy?

Answer 2

• How heat is transferred during cooking and preservation

- How energy affects the structure of food during such processes

Question 3

Define potential energy.

Answer 3

Stored energy; the work done in lifting objects to a position

Question 4

What form is Ep in food?

Answer 4

Chemical potential energy (calories)

Question 5

Define kinetic energy.

Answer 5

Energy of motion

Question 6

How does Ek relate to food?

Answer 6

Atoms and molecules always in motion

ex: heat water, atoms move faster, Ek increases

Question 7

Compare internal vs. external energy.

Answer 7

External: E applied to an object by another source
Internal: E contained in an in an object

Question 8

What kind of energy does food contain?

Answer 8

Internal potential energy

Question 9

Name the 5 forms of energy in the food industry.

Answer 9

1) Mechanical
2) Electrical
3) Radiant
4) Nuclear
5) Chemical

Question 10

Define mechanical energy.

Answer 10

Total kinetic and potential energy of a system.

Question 11

How does the body use mechanical energy?

Answer 11

When it moves

Question 12

How does the food industry use mechanical energy?

Answer 12

Food processing, for its equipment

ex: mixers, blenders, and food processors convert electrical energy to mechanical energy

Question 13

Define chemical energy.

Answer 13

Generated when bonds are broken/formed during chemical reactions

Question 14

What is an endothermic reaction?

Answer 14

Absorbs energy and lowers temperature

Question 15

What is an exothermic reaction?

Answer 15

Releases energy and increases temperature

Question 16

How does metabolism allow us to utilize chemical energy?

Answer 16

Breaks down food –> release chemical energy

Question 17

Define electrical energy.

Answer 17

Produced by the movement of electrons.

Question 18

During food processing, what is electric energy converted to?

Answer 18

Mechanical or radiant

Question 19

What is electrical energy transported by?

Answer 19

Transported through materials that are good conductors (copper, silver, etc.)

Question 20

Define radiant energy.

Answer 20

Energy transmitted in the form of waves through space or some medium

Question 21

What is another word for radiant energy?

Answer 21

Electromagnetic spectrum

Question 22

Name some examples of radiant energy.

Answer 22

Radio waves, ultraviolet waves, microwaves, electric coils, charcoal grills, gas flames, induction cooktops

Question 23

What forms of energy do microwave ovens convert?

Answer 23

Electrical energy to radiant energy

Question 24

How do microwaves work?

Answer 24

Electron tube converts electrical E into waves of radiant energy (microwaves). Then, the interior surfaces reflects microwaves towards the food which heats it up.

Question 25

Name 3 issues with microwaves.

Answer 25

- Food-borne outbreaks (ex: raw poultry) - Food not cooked properly - Carry-over cooking (food still being cooked after microwaving)

Question 26

How does induction cooking work?

Answer 26

Alternating currents --> magnetic field excites electrons -> electric current -> causes flat pan to heat

Question 27

Why do induction cooktops produce less energy waste?

Answer 27

Since they directly heat the cooking vessel

Question 28

What type of vessel needs to be used for induction cooking?

Answer 28

Ferromagnetic

Question 29

Define nuclear energy.

Answer 29

Result of splitting or combining atoms of certain elements, which then give off radiation

Question 30

How is nuclear energy used in medicine?

Answer 30

X-Rays

Question 31

How is nuclear energy used in food preservation?

Answer 31

Irradiation

Question 32

Is irradiation effective? Why don't we use it often?

Answer 32

One of the most effective, but public thinks food will be radioactive

Question 33

Define heat.

Answer 33

Heat is an energy transfer from one body to another caused by a temperature difference between the 2.

Question 34

Define a calorie.

Answer 34

One calorie is the heat needed to raise the temp of one gram of water one oC.

Question 35

Define a kilocalorie. Why do we use kilocalories?

Answer 35

One kilocalorie is the heat needed to raise the temp of one kilogram of water one oC. It simplifies calorie count

Question 36

Define heat capacity.

Answer 36

The ability of a substance to absorb heat

Question 37

What foods have high heat capacity?

Answer 37

Foods with high water content

Question 38

Define specific heat.

Answer 38

The ability of a substance to absorb or transfer heat compared to water's ability. The amount of energy needed to raise the temperature of 1g of that substance 1oC.

Question 39

Why is it important to know specific heat?

Answer 39

Helps predict how the food will react during processing

Question 40

Define temperature.

Answer 40

The measure of the average kinetic energy of a group of individual molecules.

Question 41

Temperature is an indirect measure of what?

Answer 41

Molecular motion

Question 42

What is temperature measured with?

Answer 42

Thermometer

Question 43

Why is it important to measure the temperature of food?

Answer 43

To ensure food safety and product quality

Question 44

How does heat flow?

Answer 44

Hot objects --> cold objects

Question 45

What does thermodynamics study?

Answer 45

Studies heat flow and T in relation to material properties

Question 46

Name the 3 types of heat transfers.

Answer 46

1) Conduction 2) Convection 3) Radiation

Question 47

Define conduction.

Answer 47

Transfer of heat through matter from particle to particle collisions

Question 48

Where does conduction occur?

Answer 48

Only in metals at the molecular level

Question 49

What happens to electrons during conduction?

Answer 49

Heated electrons skip over tens of hundreds of atoms and speed the heat transfer

Question 50

Define convection.

Answer 50

Transfer of heat by the motion of molecules within a liquid or a gas (water or air)

Question 51

Is conduction or convection faster?

Answer 51

Convection

Question 52

Give a common example of convection.

Answer 52

Cooking food in water

Question 53

Define radiation.

Answer 53

Transfer of heat by electromagnetic waves (browning).

Question 54

What doesn't radiation need?

Answer 54

The presence of matter

Question 55

Give examples of radiation.

Answer 55

Browning of baked goods, roasted foods, broiling, rotisserie cooking, solar oven

Question 56

What do phase changes need?

Answer 56

A flow of energy

Question 57

Gas to Solid

Answer 57

Deposition

Question 58

Solid to Gas

Answer 58

Sublimation

Question 59

Liquid to Gas

Answer 59

Evaporation

Question 60

Gas to Liquid

Answer 60

Condensation

Question 61

Solid to Liquid

Answer 61

Fusion

Question 62

Liquid to Solid

Answer 62

Crystallization

Question 63

What is the energy needed to melt/freeze called?

Answer 63

Latent heat of fusion

Question 64

What is the energy needed to evaporate/condense called?

Answer 64

Latent heat of vaporization

Question 65

What is the energy needed to complete rearranging of molecules during phase change called?

Answer 65

Latent heat

Question 66

How is the temperature at the point of a phase change?

Answer 66

T remains constant

Question 67

Why is understanding phase changes important?

Answer 67

Important in processing and preserving food products

Question 68

Name the 3 factors that affect rates of reaction in food preparation.

Answer 68

1) Temperature of reactants 2) Amount of surface area 3) Thickness of food

Question 69

If a child is swinging, the fastest speed will be at the bottom of the swinging motion when maximum ____ is reached and slowest speed at the top of the swinging motion when maximum ___ is reached.

Answer 69

Ek | Ep

Question 70

If you are sitting perfectly still, your body has _____ energy. If a friend pulls you out of your chair, your body has ____

Answer 70

External potential energy | External kinetic energy

Question 71

Where is the internal kinetic energy in your body? Internal potential energy?

Answer 71

Kinetic: molecules within body are moving and doing work Potential: fat stored as fuel for work

Question 72

A waterwheel is a form of ____ energy

Answer 72

Kinetic mechanical energy

Question 73

Making homemade ice cream by mixing salt and ice is a ____ reaction

Answer 73

endothermic reaction, lowers temperature

Question 74

Digestion is an _____ reaction

Answer 74

exothermic

Question 75

Dissolving NaOH in water is an ____ reaction

Answer 75

exothermic

Question 76

What is visible radiant energy called?

Answer 76

Light

Question 77

How do microwaves cook food?

Answer 77

Microwaves cause polar compounds to vibrate. This causes friction which produces heat.

Question 78

What kinds of foods will cook faster in a microwave?

Answer 78

Foods with high water content, or foods that are high in fats and sugar (help conduct heat)

Question 79

What are the advantages of induction cooktops?

Answer 79

- Can boil water in half the time of gas and electric stoves | - Surface of the cooktop stays relatively cool

Question 80

Why is grilling not seen as healthy?

Answer 80

Carcinogens are formed when meats are grilled

Question 81

Why is water a great cooking medium?

Answer 81

High heat capacity, rapidly absorb heat or transfer it

Question 82

Would a glass of water and a pitcher have the same heat? And temperature?

Answer 82

Temp: same Heat: different because different masses --> measure of all the kinetic energy

Question 83

When temperature is the same between two objects, how does heat flow?

Answer 83

It stops

Question 84

What type of heat transfer is a pan touching a heat source? When will the heat transfer stop?

Answer 84

Conduction | When heat source, pan, and food have the same temp

Question 85

What type of heat transfer is cooking food in water or baking? When will the heat transfer stop?

Answer 85

Convection | When the fluid is the same temperature throughout

Question 86

Frost forming on a window in a cold morning is an example of what phase change?

Answer 86

Deposition | Water vapor --> solid state

Question 87

Gas rising from dry ice is an example of what phase change?

Answer 87

Sublimation

Question 88

What phase change is used to freeze and dry foods at the same time? ex: freeze dried coffee

Answer 88

Sublimation

Question 89

If a substance is being cooled, latent heat is being ______. This occurs during ______

Answer 89

released | crystallization, condensation, deposition

Question 90

If a substance is being heated, latent heat is being ______. This occurs during ______

Answer 90

absorbed | melting, vaporization, sublimation

Question 91

T or F: The rate of a reaction approximately doubles for every 10oC increase in temperature

Answer 91

True