Q1) A circular hole in an aluminum plate is 2.725 cm in diameter at 0C. A) What

Question

Q1) A circular hole in an aluminum plate is 2.725 cm in diameter at 0C. A) What is the diameter when the temperature of the plate is raised to 100C? B) If the Aluminum plate is 0.6kg how many moles is this? C) If instead we had the same about of moles of Neon gas, how many grams would this be?

The equation is (Delta L = Lo * alpha * Delta T )

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Q2) A section of copper paneling is constructed with an area of 0.85m2and a thickness of 0.04 inches. If the copper paneling is initially lying on the ground and the ground is at a temperature of 4C and the Air is at 21.11C how much energy is conducted through the paneling in a 5 hour period? You can assume that the temperature does not change from the given values for the ground or air for that 5 hour period.

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Explanation / Answer

Your answers for Q1, A) and B) are correct.

Q1) C)

There are N =22.239 moles of Ne.

Atomic mass of Ne is

M(Ne) =20.18 g

Total mass of Ne is

m =M*N =20.18*22.239 =448.78 grams

Q2)

The equation relation the energy conducted to the temparatures on both sides is

q = k*(dT/dx)

where q is the heat flux density . That is

q = power/area =P/S

k is the copper thermal conductivity

k=401 W/(m*K)

(dT/dx) is the variation of temperature over the thickness of the plate

dT =21.11-4 =17.11 Celsius

dx =0.04 inch =0.001016 m

dT/dx =16840.55 (K/m)

With these values we have

q =P/S =401*16840.55 =6.753*10^6 (W/m^2)

For an area of S =0.85 m^2

P =q*S =5.74*10^6 W

Since by definition P =E/t, the energy for t=5 hours =5*3600 =18000 seconds is

E =P*t =18000*5.74*10^6=1.033*10^11 (J)

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