You have a mass of hot water at 90oC and twice the mass of cool water at 10oC. the hot and cold water are mixed together. will the final temperature be midway between 10 and 90oC, closer to 90oC, or closer to 10oC?

closer to 90oC

Explanation:

The heat lost by the hot water is equal to the heat gained by the cold water.

Heat loss = mcΔθ

let the mass of hot water be m then the mass of cold water will be 2m

let the final temperature be F

2m * c * (90 - F) = m * c * (F - 10)

180 - 2F = F - 10

3F = 190

F = 63.33oC

63.33 - 10 = 53.33oC

90 - 63.33 = 26.67oC

Based on the computation, the final temperature will be closer to 90oC.