How much energy is released by 44 grams of Copper (spht = 0.38 J/g C ) if its temp. falls from 333 K to 280 K?

Question

Hey I just have no idea how to approach solving this problem and ANY help you can give me would be awesome! Thank you so much for your time!

Answer 1

Look at the units given on the value for the specific heat....Joules per gram degrees C. Do you see any connection between this and what you are trying to find / what information you are given?

You are looking for an answer in terms of energy (measured in Joules). You are given a mass (in grams) and a change in temperature (measured in Kelvin, which is equivalent in terms of temperature changes to degrees C).
How can you manipulate the specific heat unit into just units of energy?
If you multiply J/g degree C by a change in temperature and a mass, you are left solely with Joules.
Using this logic, you can "build" the formula you need to use without needing to memorize it.

The formula is:
Q = mc(delta T)
where Q is the heat energy, m is the mass, c is the specific heat, and (delta T) is the change in temperature.
To find the change in temperature, subtract the initial temperature from the final temperature (final - initial).
Just plug into the equation and get the result.

The +/- sign on the answer indicates which was the heat energy flows. A negative sign indicates that the heat is flowing out of the system, which is what one would expect if the Copper is cooling off.
A postive sign on the answer would indicate that energy is flowing into the system and the object's temperature is increasing.

Also, in this case, you should not be overly concerned that the temperature change in given in Kelvin and your specific heat is given in degrees C. A change in 1 degree C is equivilent to a change in 1 Kelvin.


EDIT:
"J D", the cooling of the Copper metal from 333 K to 280 K is an exothermic process, so the sign on the answer should be negative. Energy is given off, not taken in, by the Copper metal.
However, the dissagreement over the sign of the answer is hardly an important issue since the question is more likely simply asking for the magnitude of the energy, since it already specifies which direction the heat flow is going using words.

By using the formula,
final - initial
to find the change in tempature, one would get,
280 K - 333 K = -53 K
This negative sign carries though the energy formula,
Q = mc(delta T)
to make the overall answer negative aswell.

Answer 2

Well if ur a chemistry student u wud probably no that u cud use the formula:

Mass (times) s.h.c. (times) temperature change
44g times 0.38 J/g C times ( 333k -280k)

(you could convert the temp to degrees celsius by subtracting 273 degrees from each which would be 60 C - 7C)

44g times 0.38 J/g C times 53 C
= +886.16 J
u put a plus sign before the answer to show that the reaction is postive or endothermic (because the temp dropped from 333K to 280K).... if the temperature had increased, then it would be negative or exothermic