Quiz1_sol

Quiz1_sol - raise one degree celsius or one kelvin we need...

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Phy 7A Winter 2009 Quiz 1 Solution Michael Woods January 25, 2009 1) Initial: 0.1 kg of water at -10 C and 5 kg of lead at 80 C put into thermal contact. So from the diagram we found that Δ E th,ice + Δ E bond,H 2 O + Δ E th,water + Δ E th,lead = 0 (1) m I C I Δ T ice + m I Δ H I + m I C w Δ T water + m Pb C Pb Δ T Pb = 0 (2) - m I C I T i,ice + m I Δ H I + m I C w T f + m Pb C Pb ( T f - 80 C ) = 0 (3) T f = 1 m I C w + m Pb C Pb ( m Pb C Pb T i,Pb - m I Δ H ) (4) = 15 . 49 C (5) = 288 . 5 K (6) 1

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2) We can read straight from the chart that the freezing point is 40 C and the boiling point is 210 C. The slopes of the transition regions can tell us about the speciﬁc heats in each phase of this substance. The solid phase has a small slope so we can see that when we add a lot of energy the energy only increases slightly. Thus the speciﬁc heat for the solid state is large since to
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Unformatted text preview: raise one degree celsius or one kelvin we need to add a of energy. The liquid phase is very steep and has a very small speciﬁc heat. The gas phase is between the liquid and solid, and its speciﬁc heat is between that of the liquid and solid phases. The ﬂat region at 40 ◦ C represents the heat of melting while the ﬂat region at 210 ◦ C represents the heat of vaporization. We quantify the two by noting that the heat of melting is much larger (spans a much larger energy range) than the heat of vaporization. Note that this is probably verbose; more words than you needed to use on the quiz. 2...
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Quiz1_sol - raise one degree celsius or one kelvin we need...

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