Heat:

$\overline{){\mathbf{Q}}{\mathbf{=}}{\mathbf{mC}}{\mathbf{\u2206}}{\mathbf{T}}}$

Heat of fusion:

$\overline{){\mathbf{Q}}{\mathbf{=}}{\mathbf{m}}{{\mathbf{L}}}_{{\mathbf{f}}}}$

Power:

$\overline{){\mathbf{P}}{\mathbf{=}}\frac{\mathbf{E}}{\mathbf{t}}}$

**(a)**

Heat lost while cooling water to 0 °C:

C_{w} = 4.186 J/(g•K) × (1000g/kg) = 4186 J/(kg•K)

m = 250 g (1kg/1000g) = 0.25kg

1 °C = 1 K

ΔT = (21 °C - 0 °C) = 21 °C (1K/1 °C) = 21 K

Refer to the temperature versus time graph (Figure 2) when answering the questions in Parts C through F A system consists of 250 g of water. The system, originally at T_{A} 21.0 °C, is placed in a freezer, where energy is removed from it in the form of heat at a constant rate. The figure shows how the temperature of the system takes t_{1 }= 10 min 600 s to drop to 0°C, after which the water freezes. Once the freezing is complete, the temperature of the resulting ice continues to drop, reaching temperature T_{B} after an hour. The following specific heat and latent heat values for water may be helpful.

How much energy must be transferred out of the system as heat *Q* to lower its temperature to 0°C?

Cooling Power of P is 36.6 W

At what time *t*2 will the water be completely frozen so the temperature can begin to fall below °C?

(seconds)

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