Question

A nutritionist burns 28 grams of corn chips. The heat released raises 5,000 mL of water from 22°C to 54°C. Complete the table below, assuming the corn chips are completely burned and all the heat is absorbed by the water. Complete the chart for 61 g of tomatoes if the same setup is used and the temperature increases by 4°C.

Answer 1

@JFraser can you help again?

Answer 2

Can anyone help? I'll fan and medal.

Answer 3

it's the same kind of problem as last time, find the energy absorbed by the water

Answer 4

Can you walk me through it?

Answer 5

the mass of water is 5000 g, right?

Answer 6

and the heat capacity of water is always 4.18 J/g°C?

Answer 7

@JFraser

Answer 8

@TheSmartOne can you help?

Answer 9

@Data_LG2

Answer 10

Can anyone help?

Answer 11

@randolal

Answer 12

yes, the specific heat of water is always 4.18 J/gC

Answer 13

okay. that's what I have. How do I find the total energy released?

Answer 14

hello?... @JFraser

Answer 15

the same way you found it last time\[Q = m*C_p * \Delta T\]

Answer 16

what do those stand for? m=mass and what about the others? sorry, the last perosn who helped didn't really explain. he just gave me numbers

Answer 17

@JFraser

Answer 18

m is the mass of water, C_p is the specific heat of water, and \(\Delta T\) is the change in temp.

Answer 19

okay... can the mass stay in g? @JFraser

Answer 20

ohhh m is mass of water? I thought it was the mass of the other thing

Answer 21

so that means my other one is wrong..

Answer 22

if you're using the specific heat of water, then you use the mass of water.

Answer 23

ohhhhhhh okay...

Answer 24

and \(\Delta T\) is the change in temp of the \(water\), so everything is comparing to the same stuff

Answer 25

oh, okay... does the mass stay in g or does it get converted to kg?

Answer 26

it stays in grams, because the specific heat is also in J/gC

Answer 27

ohhhh okay. thanks :)

Answer 28

then to find the amount of heat (in Joules) released by the combustion you do what?...

Answer 29

the heat released is the \(Q\) in the equation

Answer 30

no, not of the water, of the corn chips and tomatoes?

Answer 31

the heat released by the chips must be \(absorbed\) by the water, that's why you use the water, not the mass of chips first

Answer 32

wait, now I'm confused... I know how to find it in the water, but then I have to use that to find it in the corn chips.. how do I do that?

Answer 33

the energy will be equal

Answer 34

the energy \(lost\) by the burning chips must be \(gained\) by the water, which is why it heats up

Answer 35

so why in the other one did I put g/J?

Answer 36

I'm still confused. I'm sorry :/ you must be getting impatient with me.

Answer 37

i don't know, but that's upside down

Answer 38

what's upside down?

Answer 39

oops* I meant J/g

Answer 40

it should be J/g, but you're comparing two different substances: the chips, and the tomatoes. Each one is burned, and each one releases energy when it burns. The J/g RATIO of each substance is what you're asked to find

Answer 41

... I'm lost.

Answer 42

ok, let me see if i can start again in steps

Answer 43

okay.. thanks.

Answer 44

I'm sorry cx

Answer 45

when the chips burn, they release energy, ok?

Answer 46

when the chips \(release \) energy, the water \(absorbs\) it

Answer 47

yes..

Answer 48

ok

Answer 49

the \(amount\) of energy that the water absorbs will be \(equal \space to\) the energy released by the chips

the \(amount\) of energy absorbed by the water will be \[Q = m*C_p*\Delta T\] m is the mass of the water, C_p is the specific heat of water, and (\Delta T\) is the change in temp of the water

and you have all 3 of those values, so multiply them all together and get your amount of energy

Answer 50

and it's the same? I got 668800...

Answer 51

J that is

Answer 52

yes, 668,800J of energy are \(released\) from 28g of chips when burned

Answer 53

how many Joules are released \(per \space gram\) of chips?

Answer 54

do I need to do that for the question?

Answer 55

\[\frac{J}{g} = \frac{668,000J}{28g \space of \space chips}\]

Answer 56

yes, for the last part

Answer 57

and I know how to do that.. it's 23885.714.. J/g

Answer 58

but the question is How much heat (in Joules) is released by the combustion of the corn chips?

Answer 59

you already found that, its 668,800J. because Joules is energy

Answer 60

okay, exactly

Answer 61

and for tomatoes I got 83600 J

Answer 62

now find the J/g for the \(tomatoes\) just like you did for the chips

Answer 63

but why do I need to do that?

Answer 64

because the last part of the question asks you to

Answer 65

no it doesn't?...

Answer 66

read the last part, it does

Answer 67

compare the calories in one gram of tomatoes to the calories in one gram of corn chips

Answer 68

that's the last part

Answer 69

so do you still need to do that? that's why I'm so confused, I think

Answer 70

@JFraser

Answer 71

you have 2 different substances, each released a different amount of energy. it's not useful to compare energy unless you're doing it \(per \space gram\) or \(per \space ounce\) of each substance. The question is kind of backwards because it just asks you to convert to calories just to compare the chips and tomatoes.

Answer 72

how do I convert to calories? I don't understand the explanation it gives..

Answer 73

1 calorie = 4.184J, so take each amount of energy, and divide each one by 4.184, to convert the unit J into a unit of calorie

Answer 74

so\[668,800 \cancel{Joules} * \frac{1 calorie}{4.184 \cancel{Joules}}\]

Answer 75

do the same thing to the tomatoes energy

Answer 76

oh.. so for the chips it's 159847.0363?

Answer 77

that's illogical.. did I do something wrong?

Answer 78

there's too many decimals, look at your sigfigs

Answer 79

thanks for the help! :D

Answer 80

it's 160,000 calories, which is correct

Answer 81

now that's for the \(total\) sample of chips. Divide the 160,000 calories by 28grams, and you have the amount of \(calories \space per \space gram\) for the chips, and do the same thing for the tomatoes

Answer 82

ohhhhhhh dang. okay.

Answer 83

what you have is basically:

28g of chips release 160,000 calories.

61g of tomatoes release 20,000 calories

Answer 84

why'd you round?

Answer 85

because i'm lazy

Answer 86

so I shouldn't round?

Answer 87

for chips I got 5708.8 cal/g... is that right?

Answer 88

the difference between 159,847J and 160,000J is practically zero.

Answer 89

that's what i get, GJ

Answer 90

wait, why do you need the difference?

Answer 91

you don't, i'm explaining why i'm rounding

Answer 92

nevermind.. that was a dumb question.

Answer 93

i figured it out XD before I saw that

Answer 94

for tomatoes it's 327.56cal/g right?

Answer 95

so that's it? I'm done?