chapter5-energy

Question 1

when does scientist start to understand energy?

Answer 1

1800

Question 2

what is internal energy?

Answer 2

result of forces between the atoms and molecules of a system.

Question 3

example for internal potential energy?

Answer 3

body fat and glycogen.

Question 4

example for mechanical energy

Answer 4

water wheel

Question 5

what is metabolism?

Answer 5

use body to convert stored chemical energy in food

Question 6

how electrons moves?

Answer 6

from - to +

Question 7

examples of radiant energy?

Answer 7

radio waves , ultraviolet waves and microwaves.

Question 8

example of electrical energy?

Answer 8

lamps–>light.
toaster–>heat.
lamp and toaster属于radiant energy
blender–>mechanical energy

Question 9

example of radiant energy?

Answer 9

electric coils, charcoal grills and gas flames–>cook food.

Question 10

what does magnetron do?

Answer 10

electrical energy–>microwaves.

Question 11

how does microwave travel? how they reflected?

Answer 11

straight lines, reflected by metals

Question 12

what does microwave cause?

Answer 12

polar compound(water) to vibrate–> friction–>heat
more water in food, faster the food will cook
also quick if food are high in sugar and fats

Question 13

what are low frequency long wavelength?

Answer 13

radio wave
microwave–>cook
infrared wave–>heat, only absorb in the surface

Question 14

what are high frequency short wavelength?

Answer 14

UV–>kill bacteria, food preservation, produce VD
X ray
gamma ray–>food preservation: irradiation, destroy living organisms could cause spoilage

Question 15

what is the frequency of rapid electrical pulse? what does it do?

Answer 15

10000per second.

kill microorganisms and inactive enzymes that present in food.

Question 16

what does induction cooktops use?

Answer 16

electromagnetic waves to generate heat in food.–>special pan need–> current crate magnetic field–>produce low electric current–>heat时间更短

Question 17

microwave safety. 5 points

Answer 17

vent plastic wrap used to cover food container
pierce whole fruit and veges have tough, unbroken skins
never hard-cook or soft-cook eggs in their shell
no aluminum foil–>cause sparks to jump from foil to walls.
no metals

Question 18

what is the cancer causing substance name?

how to prevent?

Answer 18

• carcinogens–>when meat grilled. not vege and fruits
• no more than 1-2 per week, use gas to grill
• clean grill before use
• bone-side down
• add vinegar or lemon juice speed cooking
• reduce grill time-precook,use marinades 10%soy sauce and 1%sugar decrease 60% carcinogens.
• turn by tongs , not folk reduce dripping, which cause flame flare-ups

Question 19

what are factors influence individual’s calorie?

Answer 19

hormones
activity level
type of food
mineral level
age
sex
sleep level
genetics
stress
illness

Question 20

what is basal metabolism?

Answer 20

body need calories to support basic functions such as breathing, blood circulation and cell growth and repair.
突然降低或升高10%体重会降低新陈代谢

Question 21

what are 2 factors make up the balance of your daily calorie need?

Answer 21

physical activity and energy used to process the food you eat

Question 22

why food scientist measure food energy?

Answer 22

know capacity to produce heat

Question 23

what is heat capacity?

how is water’s heat capacity?

Answer 23

ability to absorb heat

greatest

Question 24

what cause a convection current?

Answer 24

fluid heat–>molecules push farther apart–>density of fluid decrease

Question 25

what does convection use?

Answer 25

boil water

baking

Question 26

what cooking method use radiation?

Answer 26

broiling and rotisserie cooking

Question 27

when is sublimation use?

Answer 27

in food industry to freeze and dry food at same time

Question 28

sublimation?

Answer 28

solid to gas

Question 29

deposition?

Answer 29

gas to solid

Question 30

what is dry ice?

Answer 30

solid carbon dioxide

Question 31

if a substance is being cooled, what happen to latent heat? when does it occur?

Answer 31

being release

during condensation, deposition, freezing

Question 32

if a substance is being heated, what happen to latent heat? when does it occur?

Answer 32

absorbed

melt, sublimation, vaporization

Question 33

what affect rate of reaction in food preparation?

Answer 33

enzyme
SA
thickness
temp

Question 34

what you do if you want to speed up cook?

Answer 34

increase SA, temp and decrease the distance to the center

If too thick, use lower power level to avoid overcooking the surface