Need Help Please Answer (1 Viewer)

[cemeteryangel1]

I really need these questions answered so if you know them please e-mail the answers 2 me. Just write the Question # and the answer. THANX IT IS GREATLY APPRECIATED.

1. What is Energy?
2. How can energy be measured?
3. What are the units for energy?
4. How would you record a quantitative change in energy?
5. What is the difference between KiloJoules and Joules?
7. What is the relationship between energy and calories?
8. What is the conversion factor for joules to calories?
9. What is a saltine composed of? Protein Carbs, or fat?
10. What is a peanut composed of? Protein Carbs, or fat?
11. How does the composition of a food affect the amount of energy it gives of? Why?
12. Why would you do an energy experiment 3 times for both the saltine and the peanut?


My e-mail is cemeteryangel12aol.com THANX AGAIN!!!!
Please e-mail dont post

 

[Dreamerish*~]

this isn't production of materials...

 

[Slidey]

Might I suggest that you try Google? Google can even convert from joules to cals for you. Type something like "10 joules to calories".

 

[snoopy05]

prelim chem.

why cant we post it here, i could answer those, but i cant be bothered if i have to email it . .@_@

 

[xiao1985]

cuz he will never come bak n check again?!?!
n taht email ain't legit either...w here's the at?!?!

and i wud highly recommend u attempt to answer the q THEN come here ask for help... it's for ur own good...

 

[Dreamerish*~]

hey, she said email not post... so does that mean she's not reading any of our replies?... lol

 

[funking_you]

cemeteryangel1,


1. What is Energy?
Refer to Prelim Textbook

2. How can energy be measured?
This is a VERY general questions, think more along the lines of 'chemical energy & heat', e.g. when you burn (combust) petrol, it releases heat energy...how could you measure this? or when your put 2 batteries in your remote control, they turn chemical energy into electrical energy? how might you meausre this electrical energy?

3. What are the units for energy?
Prelim Textbook

4. How would you record a quantitative change in energy?
Think of a specific example, e.g. look up 'calorimetry' in your prelim texbook.

5. What is the difference between KiloJoules and Joules?
Prelim textbook! (but note the difference is the work 'kilo')

7. What is the relationship between energy and calories?
Prelim textbook

8. What is the conversion factor for joules to calories?
Prelim textbook, and/or googe!

9. What is a saltine composed of? Protein Carbs, or fat?
Google it

10. What is a peanut composed of? Protein Carbs, or fat?
Google it

11. How does the composition of a food affect the amount of energy it gives of? Why?
Think bout it, then google it!

12. Why would you do an energy experiment 3 times for both the saltine and the peanut?
I'll re-phrase the question, "why would you want to repeat an experiment?

 

[Dreamerish*~]

wow
clap clap for the chem coach
but she's not coming back here '-_- she wants it emailed *mocks*

 

[funking_you]

they cant have it all their way!

 

[Dreamspirit]

For chemistry, isn't it just making notes, knowing the prac by actually doing it and understanding it, and revising both that?

 

[Slidey]

I'd say it's a bit more than just rote learning... but yes, it'll help.

But you need to truely KNOW the concepts and the things you do or write.

That's why it is better to make your own notesw than copy another's.

 

[Pointy Ears]

u no, i get the feeling that this is just an assignment and that she couldnt be bothered to find the answers herself, i mean, these answers are easy as hell to find in the textbook.

 

[Uncle]

Some shouldn't even be referred to a textbook, these should be known:

1. What is Energy?
The ability to do work.

3. What are the units for energy?
SI Unit: Joules (J)
Derived Units: Newton-metre (N.m), Watt-second (W.s)
Go do some dimensional analysis and you can derive them from fundamental units like mass, displacement or time.

5. What is the difference between KiloJoules and Joules?
A kilo always multiplies a quantity by 10³.



A reminder to all HSC Chemistry students on the heat energy equation used in the HSC i.e. Q = mcΔT
The assumptions are:

* Constant specific heat with changing temperature.
That means the specific heat does NOT change with temperature.
In reality the specific heat does change with temperature and the proper expression is:

But this isn't in the syllabus so don't worry.


* Constant state of matter.
That means you must be working with a substance that is still in its current phase within its range of temperature,
e.g. when working with water the temperature range must be between 0⁰C and 100⁰C

If some idiot gives you a question to find the heat energy added to 500g of water from 5^oC to 120^oC and says
Q = (0.500kg)(4186 J.kg^-1.^oC^-1)(120^oC - 5^oC) the actual result is entirely INCORRECT.
Water boils and changes state at 100^oC and requires ADDITIONAL energy to change from liquid to gas which is SEPARATE from the calorimetry equation
i.e. Q = mL where L is the latent heat of fusion (solid to liquid) or vaporisation (liquid to gas) of a substance.

The correct answer would have been:
Q = mcΔT_water + mL_vap + mcΔT_steam
Q = m(cΔT_water + L_vap + cΔT_steam)
Q = (0.5kg)[(4186 J.kg^-1.^oC^-1)(100^oC - 5^oC) + (2.26x10⁶ J.kg^-1) + (4186 J.kg^-1.^oC^-1)(120^oC - 100^oC)]

Notice the value for L is much bigger than c, a lot of energy is used to separate those molecules in water to become steam than merely giving more energy for the molecules to move faster in their current state, so using Q = mcΔT alone is stupid.

Then again it isn't in the syllabus.