1. Nov 21, 2012

I need help with a question. I think I have an answer, but don't know if it's right. It also doesn't add up to 0 if I plug in the final temperture into the equation. But I keep getting the same answer. Help please!

A 150 g piece of copper at 90°C is placed in 250 g of water at 20°C. Assume that no heat escapes into the surroundings. Find the final temperature of the mixture.

mass of copper: (0.150kg)
specific heat capacity: (390J/(kg°C))
temperture of copper: (t2-90°C)

mass of water: (0.250kg)
specific heat capacity: (4200J/(kg°C))
temperture of water: (t2-20°C))

equation: (mass of copper)(spec. heat cap.)(final temp - intial temp) + (mass of water)(spec. heat cap.)(final temp - initial temp) = 0

(0.150kg)(390J/(kg°C))(t2-90°C)+(0.250kg)(4200J/(kg°C))(t2-20°C))=0
1108.5t2=26265
t2 = 23.7°C

2. Nov 21, 2012

Heat Exchange of Copper and Water

1. The problem statement, all variables and given/known data

I need help with a question. I think I have an answer, but don't know if it's right. It also doesn't add up to 0 if I plug in the final temperture into the equation. But I keep getting the same answer. Help please!

A 150 g piece of copper at 90°C is placed in 250 g of water at 20°C. Assume that no heat escapes into the surroundings. Find the final temperature of the mixture.

mass of copper: (0.150kg)
specific heat capacity: (390J/(kg°C))
temperture of copper: (t2-90°C)

mass of water: (0.250kg)
specific heat capacity: (4200J/(kg°C))
temperture of water: (t2-20°C))

2. Relevant equations

equation: (mass of copper)(spec. heat cap.)(final temp - intial temp) + (mass of water)(spec. heat cap.)(final temp - initial temp) = 0

3. The attempt at a solution

(0.150kg)(390J/(kg°C))(t2-90°C)+(0.250kg)(4200J/(kg°C))(t2-20°C))=0
1108.5t2=26265
t2 = 23.7°C

3. Nov 21, 2012

### ehild

Re: Heat Exchange of Copper and Water

Correct solution!

ehild

4. Nov 21, 2012

### haruspex

It's just rounding error. If you plug in 23.6942 you'll get something close to 0. But don't change your answer to that. 23.7 C is fine.

5. Nov 21, 2012