Math Problem Statement

Finnish saunas can reach temperatures as high as 130 - 140 degrees Celcius - which extreme sauna enthusiasts can tolerate in short bursts of 3 - 4 minutes. Calculate the heat required to convert a 0.6 kg block of ice, brought in from an outside temperature of -19 degrees Celcius, to steam at 110.5 degrees Celcius in the sauna. [The specific heat capacity of water vapour is 1.996 kJ/kg/K; see the lecture notes for the other specific heat capacities and specific latent heats].

Solution

To calculate the total heat required to convert a 0.6 kg block of ice at -19°C to steam at 110.5°C, we need to consider several steps involving heating and phase changes. Here's the breakdown:


Step 1: Heat the ice from -19°C to 0°C

The formula for heat transfer is: q=mcΔTq = mc\Delta T where:

  • m=0.6kgm = 0.6 \, \text{kg} (mass of ice),
  • cice=2.1kJ/kg/°Cc_{\text{ice}} = 2.1 \, \text{kJ/kg/°C} (specific heat capacity of ice),
  • ΔT=(0(19))=19°C\Delta T = (0 - (-19)) = 19 \, \text{°C}.

q1=0.6×2.1×19=23.94kJq_1 = 0.6 \times 2.1 \times 19 = 23.94 \, \text{kJ}


Step 2: Melt the ice at 0°C to water

The heat required for phase change is: q=mLfq = mL_f where:

  • Lf=334kJ/kgL_f = 334 \, \text{kJ/kg} (specific latent heat of fusion for ice).

q2=0.6×334=200.4kJq_2 = 0.6 \times 334 = 200.4 \, \text{kJ}


Step 3: Heat the water from 0°C to 100°C

q=mcΔTq = mc\Delta T where:

  • cwater=4.2kJ/kg/°Cc_{\text{water}} = 4.2 \, \text{kJ/kg/°C} (specific heat capacity of water),
  • ΔT=100°C\Delta T = 100 \, \text{°C}.

q3=0.6×4.2×100=252kJq_3 = 0.6 \times 4.2 \times 100 = 252 \, \text{kJ}


Step 4: Convert water at 100°C to steam at 100°C

q=mLvq = mL_v where:

  • Lv=2260kJ/kgL_v = 2260 \, \text{kJ/kg} (specific latent heat of vaporization for water).

q4=0.6×2260=1356kJq_4 = 0.6 \times 2260 = 1356 \, \text{kJ}


Step 5: Heat the steam from 100°C to 110.5°C

q=mcΔTq = mc\Delta T where:

  • csteam=1.996kJ/kg/°Cc_{\text{steam}} = 1.996 \, \text{kJ/kg/°C} (specific heat capacity of water vapor),
  • ΔT=110.5100=10.5°C\Delta T = 110.5 - 100 = 10.5 \, \text{°C}.

q5=0.6×1.996×10.5=12.56kJq_5 = 0.6 \times 1.996 \times 10.5 = 12.56 \, \text{kJ}


Total Heat Required:

Qtotal=q1+q2+q3+q4+q5Q_{\text{total}} = q_1 + q_2 + q_3 + q_4 + q_5 Qtotal=23.94+200.4+252+1356+12.56=1844.9kJQ_{\text{total}} = 23.94 + 200.4 + 252 + 1356 + 12.56 = 1844.9 \, \text{kJ}


Final Answer:

The total heat required is 1844.9 kJ.


Would you like a detailed breakdown of any specific step?

Related Questions:

  1. What would happen if the initial temperature of the ice was even lower, say -40°C?
  2. How does the specific heat capacity of water compare to that of ice and steam?
  3. How would the calculation change if the mass of ice were doubled?
  4. What physical phenomena account for the large latent heat values for fusion and vaporization?
  5. How can this knowledge be applied to real-world energy calculations in saunas?

Tip:

Always check the units in thermal energy problems to avoid errors in conversions and ensure accuracy!

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Math Problem Analysis

Mathematical Concepts

Thermodynamics
Heat transfer
Phase changes in matter

Formulas

q = mcΔT
q = mL
Q_total = q1 + q2 + q3 + q4 + q5

Theorems

Conservation of Energy in Thermal Systems

Suitable Grade Level

Grades 11-12 and College