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Use a computer to study the entropy, temperature, and heat capacity of an Einstein solid, as follows. Let the solid contain 50 oscillators (initially), and from 0 to 100 units of energy. Make a table, analogous to Table 3.2, in which each row represents a different value for the energy. Use separate columns for the energy, multiplicity, entropy, temperature, and heat capacity. To calculate the temperature, evaluate ΔU/ΔSfor two nearby rows in the table. (Recall that U=qϵfor some constant ϵ.) The heat capacity (ΔU/ΔT)can be computed in a similar way. The first few rows of the table should look something like this:

(In this table I have computed derivatives using a "centered-difference" approximation. For example, the temperature .28is computed as 2/(7.15-0).) Make a graph of entropy vs. energy and a graph of heat capacity vs. temperature. Then change the number of oscillators to 5000 (to "dilute" the system and look at lower temperatures), and again make a graph of heat capacity vs. temperature. Discuss your prediction for the heat capacity, and compare it to the data for lead, aluminum, and diamond shown in Figure 1.14. Estimate the numerical value of εin electron-volts, for each of those real solids.

Short Answer

Expert verified

The table can be prepared as:

The graphs can be made as:

For 50 oscillations

For 5000 oscillations

The values of εare:

εlead=6.875×10−3eVεaluminium=2.587×10−2eVεdiamond=0.19233eV

Step by step solution

01

Given Information

The given Einstein solid contains 50 oscillators from 0 to 100 units of energy.

That is,

N=50q=1to100

U=qϵ

02

Calculation for table values

The entropy of the system is given as:

Sk=lnΩSk=lnq+N-1⌊q⌊N-1

The temperature is given as:

1T=∂S∂UT=ΔUΔST=Δ(εq)Δ(klnΩ)kTϵ=Δ(q)Δ(lnΩ)

Heat capacity per oscillation is given as:

CN=ΔUNΔTCN=Δ(εq)NΔΔ(εq)Δ(klnΩ)CNk=Δ(q)NΔΔ(q)Δ(lnΩ)

The table consisting of entropy, temperature, and heat capacity of an Einstein solid for 50 oscillations with 0 to 100 units of energy can be prepared as follows:

03

Graph

The graphs of entropy vs energy and heat capacity vs temperature can be sketched as follows:

For 50 oscillations:

The graph of entropy vs energy can be made as:

The graph of heat capacity vs temperature can be made as:

For 5000 oscillations:

The graph of entropy vs energy can be made as:

The graph of heat capacity vs temperature can be made as:

The heat capacity is substantially smaller than the values in figure 1.14, since, for 5000 oscillations with the same units of energy, the energy is lowered, lowering the system's temperature.

04

Calculation of ε

For q=1,Ω=1

Solving for ε,we get,

U=ϵqε=Uqϵ=Tk(lnΩ)qε=kT

For lead, heat capacity is maximum at T=80K

εlead=kTεlead=1.38×10-23×80εlead=1.1×10-21Jεlead=6.875×10-3eV

For aluminum heat capacity is maximum at T=300K

εaluminum=kTεaluminum=1.38×10-23×300εaluminum=4.14×10-21Jεaluminum=2.587×10-2eV

For diamond heat capacity is maximum at T=2230K

εdiamond=kTεdiamond=1.38×10-23×2230εdiamond=3.0774×10-20Jεdiamond=0.19233eV

05

Final answer

The table of the values can be prepared as:

The graphs can be prepared as:

For 50 oscillations:

For 5000 oscillations:

The value of εare:

ϵlead=6.875×10−3eVϵaluminium=2.587×10−2eVϵdiamond=0.19233eV

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Most popular questions from this chapter

Use a computer to reproduce Table 3.2 and the associated graphs of entropy, temperature, heat capacity, and magnetization. (The graphs in this section are actually drawn from the analytic formulas derived below, so your numerical graphs won't be quite as smooth.)

Consider a monatomic ideal gas that lives at a height z above sea level, so each molecule has potential energy mgzin addition to its kinetic energy.

(a) Show that the chemical potential is the same as if the gas were at sea level, plus an additional term mgz:

μ(z)=-kTlnVN2πmkTh23/2+mgz.

(You can derive this result from either the definition μ=-T(∂S/∂N)U,Vor the formula μ=(∂U/∂N)S,V.

(b) Suppose you have two chunks of helium gas, one at sea level and one at height z, each having the same temperature and volume. Assuming that they are in diffusive equilibrium, show that the number of molecules in the higher chunk is

N(z)=N(0)e-mgz/kT

in agreement with the result of Problem 1.16.

When the sun is high in the sky, it delivers approximately 1000 watts of power to each square meter of earth's surface. The temperature of the surface of the sun is about 6000K, while that of the earth is about 300K.

(a) Estimate the entropy created in one year by the flow of solar heat onto a square meter of the earth.

(b) Suppose you plant grass on this square meter of earth. Some people might argue that the growth of the grass (or of any other living thing) violates the second law of thermodynamics, because disorderly nutrients are converted into an orderly life form. How would you respond?

A liter of air, initially at room temperature and atmospheric pressure, is heated at constant pressure until it doubles in volume. Calculate the increase in its entropy during this process.

In order to take a nice warm bath, you mix 50 liters of hot water at 55°C with 25 liters of cold water at 10°C. How much new entropy have you created by mixing the water?

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