How much heat does it take to increase 2 kilograms of the following:
a) air
b) liquid water
c) aluminum from 27 C to 77 C? (Hint: K = 273 + C)
In this case, the fi rst law, Q = ?U + ?PE + ?KE + W, reduces Q = ?U as
there is no work, change of kinetic power, or change of potential energies.
?U = m c (?T). Air ?U = (2 kg)(1.004 kJ/kg-K)(50 K) = 100.4 kJ; 418.6 kJ
water; 96.3 kJ aluminum
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