**Solving specific heat—physics problem. HELP!?**

Please help me solve this problem. I’ve been working on this for like 3 hours and have not yet come up with an answer. If you get an answer, can you please show your work?

—

A hot, just-minted copper coin is placed in

116 g of water to cool. The water temperature

changes by 8.00 °C and the temperature of the

coin changes by 87.3 °C.

What is the mass of the coin? Disregard

any energy transfer to the water’s surround-

ings and assume the specific heat of copper

is 387 J/kg°C. The specific heat of water is

4186 J/kg°C.

Answer in units of g.

—

Thanks so much.

OK … here we go:

The energy absorbed by the water is:

E = 4184J/(kg*C)*8C*0.160kg = 495.36J

For the copper, we want to know the mass so let’s multiply its specific heat by what we know and see what happens. Note: we must use the inverse of the specific heat to get the units right and get an answer in grams. Lets try:

(kg*C/387J)*(495.36J/87.3C) = 0.014662kg or 14.662g

Lets check it just to make sure.

E = 387J/(kg*C)*87.3C*0.014662kg = 495.36J

Both the copper and the water exchanged the same number of joules!

The answer is 14.662 grams of copper.

Best,

Dave

**Physics: Thermodynamic processes (1)**