2 replies to this topic

[Linnsan]

I'm going through old paper 1 exams and stumbled upon the following question which I'd like some help solving. I'll show you what I have managed to do so far.

"A block of metal at a temperature of 90 C is placed in a beaker of water at a temperature of 0 C. The mass of the metal block and the mass of the water are equal. The final temperature of the water and the metal block is 9 C.
Which of the following is the best estimate of the ratio: specific heat of water/specific heat of metal?"

I thought the following. The heat lost by the metal= the heat gained by the water.

So: m * c_metal * (T_min-T_max) = m * c_water * (T_max-T_min)

Cancelling both masses since they're equal and putting in the temperatures gives:

c_m * (9-90)= c_w* (90-9)
c_m * (-81)= c_w* 81

That's where I got stuck. Have I done something wrong?

The alternatives are A: 1/10 B: 1/9 C: 9 10 and the correct answer is C: 9.

Please help, and thanks in advance

[HiggsHunter]

Yes, you should have Cm * (90-9) = Cw * (9-0)
So Cw/Cm = 81/9 = 9 (Answer C)

[Linnsan]

Ahhhh thanks. It was the 0 that got lost into space