Please help clarify which is the correct answer and or method to the following problem:
Ideally, when a thermometer is used to measure the temperature of an object, the temperature of the object itself should not change. However, if a significant amount of heat flows from the object to the thermometer, the temperature will change. A thermometer has a mass of 31 g, a specific heat capacity of 815 J/kg·°C, and a temperature of 12°C. It is immersed in 119 g of water, and the final temperature of the water and thermometer is 41.5°C. What was the temperature of the water before the insertion of the thermometer?
The answer posted by the instructor is 43 degrees C.
I am confused because I'm getting conflicting instructions from different sources, or maybe I'm just not understanding the full concept.
The instructor's way uses:
m1c1(TfTi) = m2c2(TfTi)
with this I got 40 degrees C.
Another source instructed to use:
m1c1(TfTi) = m2c2(TiTf)
with this I got 43 degrees C.
I do understand that Q=m1c1(TfTi).
So, is the posted answer incorrect, or is the instructor's method incorrect, or is it just my calculation? Thanks and much appreciated! The attached image shows my work.
Ideally, when a thermometer is used to measure the temperature of an object, the temperature of the object itself should not change. However, if a significant amount of heat flows from the object to the thermometer, the temperature will change. A thermometer has a mass of 31 g, a specific heat capacity of 815 J/kg·°C, and a temperature of 12°C. It is immersed in 119 g of water, and the final temperature of the water and thermometer is 41.5°C. What was the temperature of the water before the insertion of the thermometer?
The answer posted by the instructor is 43 degrees C.
I am confused because I'm getting conflicting instructions from different sources, or maybe I'm just not understanding the full concept.
The instructor's way uses:
m1c1(TfTi) = m2c2(TfTi)
with this I got 40 degrees C.
Another source instructed to use:
m1c1(TfTi) = m2c2(TiTf)
with this I got 43 degrees C.
I do understand that Q=m1c1(TfTi).
So, is the posted answer incorrect, or is the instructor's method incorrect, or is it just my calculation? Thanks and much appreciated! The attached image shows my work.
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