Find the relative mass of the blocks (thermochemistry)

[Ritzycat]

Homework Statement

A block of copper at 100.0° C comes into contact with a block of aluminum at 20.0°C. The final temperature of the blocks is 60.0°C. What are the relative masses of the blocks?

Homework Equations

mcΔT
copper specific heat = .386 J/g°C
aluminum specific heat = .900 J/g°C

The Attempt at a Solution

(x)(.386 J/g°C)(40°C) = (x)(.900 J/g°C)(-40°C)
what I use to try to find the mass, assuming that the energy lost in one part of the system is gained by the other... Also, what is meant by "relative" mass in this question?

Until I realize this equation cannot be solved...

Any help is appreciated not really sure how to go about doing this problem, I feel like I am missing something because this should be very easy.

 

[tiny-tim]

Hi Ritzycat!

… What are the relative masses of the blocks?
… what is meant by "relative" mass in this question?

I think they mean: what is the ratio of the two masses (ie what is one mass relative to the other).

(imo, this is not a correct use of the words "relative masses" )

 

[Ritzycat]

Thanks for the response.

If the question is referring to ratio, wouldn't the ratio of their masses simply be the ratio of the specific heat capacities? (given the absolute value of delta T is the same)

 

[Yanick]

What can you say about the heat loss/gain of each block?

 

[Borek]

If the question is referring to ratio, wouldn't the ratio of their masses simply be the ratio of the specific heat capacities? (given the absolute value of delta T is the same)

Only if you can prove it. Just write heat balance using m_{Al} and m_{Cu} and solve for \frac {m_{Al}} {m_{Cu}}.