Step 1: Calculate the heat supplied by the electric heater.
The heat supplied by the heater is given by the formula Q=VIt.
Given:
Voltage V=1.6V
Current I=0.1A
Time t=15min=15×60s=900s
Qheater=(1.6V)(0.1A)(900s)
Qheater=144J
Step 2: Calculate the heat gained by the ice.
The problem states "a piece of ice of mass 2kg is added at a temperature of 2∘C" and also provides the "latent heat capacity of ice". Ice cannot exist at 2∘C. This is a common ambiguity in physics problems. We will assume the intention is that the ice is at 0∘C, melts, and then the resulting water warms up. If it were already water at 2∘C, the latent heat would not be relevant.
First, calculate the heat required to melt the ice at 0∘C:
Qmelt=miceLf
Given:
Mass of ice mice=2kg
Latent heat of fusion of ice Lf=336000Jkg−1
Qmelt=(2kg)(336000Jkg−1)
Qmelt=672000J
Next, calculate the heat required to warm the melted ice (now water) from 0∘C to the final temperature Tf:
Qwarm,icewater=micecwater(Tf−0\circC)
Given:
Specific heat capacity of water cwater=4200Jkg−1K−1
Qwarm,icewater=(2kg)(4200Jkg−1K−1)(Tf)
Qwarm,icewater=8400TfJ
The total heat gained by the ice is:
Qicetotal=Qmelt+Qwarm,icewater
Qicetotal=672000+8400Tf
Step 3: Calculate the heat lost by the initial water and the copper calorimeter.
The initial temperature of the water and the calorimeter is 30∘C.
Heat lost by the initial water:
Qwaterloss=mwatercwater(Tinitial,water−Tf)
Given:
Mass of initial water mwater=40kg
Initial temperature of water Tinitial,water=30∘C
Qwaterloss=(40kg)(4200Jkg−1K−1)(30\circC−Tf)
Qwaterloss=168000(30−Tf)J
Heat lost by the copper calorimeter:
Qcopperloss=mcopperccopper(Tinitial,copper−Tf)
Given:
Mass of copper calorimeter mcopper=1.5kg
Specific heat capacity of copper ccopper=400Jkg−1K−1
Initial temperature of copper Tinitial,copper=30∘C
Qcopperloss=(1.5kg)(400Jkg−1K−1)(30\circC−Tf)
Qcopperloss=600(30−Tf)J
The total heat lost by the warmer components is:
Qlosstotal=Qwaterloss+Qcopperloss
Qlosstotal=168000(30−Tf)+600(30−Tf)
Qlosstotal=(168000+600)(30−Tf)
Qlosstotal=168600(30−Tf)
Qlosstotal=5058000−168600Tf
Step 4: Apply the principle of conservation of energy.
Assuming negligible heat loss to the surroundings, the total heat supplied by the heater plus the heat lost by the warmer components equals the total heat gained by the colder components.
Qheater+Qlosstotal=Qicetotal
144+(5058000−168600Tf)=672000+8400Tf
5058144−168600Tf=672000+8400Tf
Rearrange the equation to solve for Tf:
5058144−672000=8400Tf+168600Tf
4386144=177000Tf
Tf=1770004386144
Tf≈24.78047∘C
Rounding to two decimal places, the final temperature is:
Tf≈24.78∘C
The final temperature of the mixture is 24.78\circC.
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