Question

How much heat will it take to get 0 kg of water from 20 kg of ice at -20 oC?

Answer 1

Step 1: Heat required to raise the temperature of ice from -20 °C to 0 °C Use the formula

q = mcΔT

where
q = heat energy
m = mass
c = specific heat
ΔT = change in temperature

q₁ = (20*10^3 g)x(2.09 J/g·°C)[(0 °C - -20 °C)]
q₁ =836000 J

Step 2: Heat required to convert 0 °C ice to 0 °C water

Use the formula for heat:

q = m·ΔH_f

where
q = heat energy
m = mass
ΔH_f = heat of fusion

q₂ = (20*10^3 g)x(334 J/g)
q₂ = 6680000 joules

total heat = q1+q2 = 836000+6680000 = 7516000 J = 7.516 × 10⁶ J answer

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