High-altitude mountain climbers do not eat snow, but always melt it first with a

Question

High-altitude mountain climbers do not eat snow, but always melt it first with a stove.

Part A

To see why, calculate the energy absorbed from your body if you eat 0.80 kg of -12 C snow which your body warms to body temperature of 37C.

Express your answer to two significant figures and include the appropriate units.

Q=

Part B

Calculate the energy absorbed from your body if you melt 0.80 kg of -12 C snow using a stove and drink the resulting 0.80 kg of water at 5 C, which your body has to warm to 37C.

Express your answer to two significant figures and include the appropriate units.

Q=

Explanation / Answer

Specific heat capacity of snow (ice) { 2.1 kJ/kg.°C }
Specific heat capacity of water { 4.2 kJ/kg.°C }
Latent heat of fusion of ice { 333 kJ/kg }

Solve using:
Heat energy = mass * specific heat * change in temperature
Heat energy = mass * Latent heat of fusion

(a)

Total heat energy required =

Energy to raise temperature of 0.8 kg of ice from -12°C to ice at 0°C
+
Energy to change 0.8 kg of ice at 0°C to 0.8 kg at water at 0°C
+
Energy to raise temperature of 0.8 kg of water from 0°C to 37°C

= (0.8 kg * 2.1 kJ/kg.°C * 12°C) + (0.8 kg * 333 kJ/kg) + (0.8 kg * 4.2 kJ/kg.°C * 37°C)
= 20.16 kJ + 266.4 kJ + 124.32 kJ
= 410.88 kJ
= 4.1088 * 10^5 J

(b)
Energy required to change 0.8 kg of water at 5°C to water at 32°C
= 0.8 kg * 4.2 kJ/kg.°C * (37 - 5)°C
= 107.52 kJ
= 1.0752 x 10^5 J

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