Calculate the condensate temperature for liquid helium-4, pretending that liquid is a gas of noninteracting atoms. Compare to the observed temperature of the superfluid transition, 2.17K. ( the density of liquid helium-4 is 0.145g/cm3)

Short Answer

Expert verified

The condensate temperature for liquid helium-4 is 3.13K

Step by step solution

01

Step 1. Given information

Condensate temperature for a given substance =

Tc=1k0.527h22πmNV23

massofparticle,m=4(1.66×10-27)kg

For density of H4eliquid,

mHeV=0.145g/cm3

Now,

NV=mHeVmHeN

Putting the values of mHeV=0.145g/cm3andmHeN=4.00g/mol.

NV=0.145×103g/cm34.00g/mol

=0.036mol/cm3

=0.036mol/cm36.022×1023atoms1mole106cm31m3

=2.18×1028atoms/m3

02

Step 2. Putting the values of h, N/V, k, m in equation Tc=1k0.527h22πmNV23

we get,

Te=11.381×10-23J/K(0.527)6.63×10-34J·s22π(4)1.66×10-27kg2.18×1028atoms/m323

=3.13K

Therefore the condensate temperature for liquid helium-4 is 3.13K.

This value is similar to experimental value of 2.17K, neglecting all the interaction between Heatoms

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Most popular questions from this chapter

Figure 7.37 shows the heat capacity of a Bose gas as a function of temperature. In this problem you will calculate the shape of this unusual graph.

(a) Write down an expression for the total energy of a gas of Nbosons confined to a volume V, in terms of an integral (analogous to equation 7.122).

(b) For T<Tcyou can set μ=0. Evaluate the integral numerically in this case, then differentiate the result with respect to Tto obtain the heat capacity. Compare to Figure 7.37.

(c) Explain why the heat capacity must approach 32Nkin the high- Tlimit.

(d) For T>Tcyou can evaluate the integral using the values of μcalculated in Problem 7.69. Do this to obtain the energy as a function of temperature, then numerically differentiate the result to obtain the heat capacity. Plot the heat capacity, and check that your graph agrees with Figure 7.37.

Figure 7.37. Heat capacity of an ideal Bose gas in a three-dimensional box.

If you have a computer system that can do numerical integrals, it's not particularly difficult to evaluate μfor T>Tc.

(a) As usual when solving a problem on a computer, it's best to start by putting everything in terms dimensionless variables. So define t=T/Tc,c=μ/kTc,andx=ϵ/kTc. Express the integral that defines μ, equation N=0g(ϵ)1e(ϵ-μ)/kT-1dϵ, in terms of these variables, you should obtain the equation

2.315=0xdxe(x-c)/t-1

(b) According to given figure , the correct value of cwhen T=2Tc, is approximately -0.8. Plug in these values and check that the equation above is approximately satisfied.

(c) Now vary μ, holding Tfixed, to find the precise value of μfor T=2Tc. Repeat for values ofT/Tcranging from 1.2up to 3.0, in increments of 0.2. Plot a graph of μas a function of temperature.

Consider a system of five particles, inside a container where the allowed energy levels are nondegenerate and evenly spaced. For instance, the particles could be trapped in a one-dimensional harmonic oscillator potential. In this problem you will consider the allowed states for this system, depending on whether the particles are identical fermions, identical bosons, or distinguishable particles.

(a) Describe the ground state of this system, for each of these three cases.

(b) Suppose that the system has one unit of energy (above the ground state). Describe the allowed states of the system, for each of the three cases. How many possible system states are there in each case?

(c) Repeat part (b) for two units of energy and for three units of energy.

(d) Suppose that the temperature of this system is low, so that the total energy is low (though not necessarily zero). In what way will the behavior of the bosonic system differ from that of the system of distinguishable particles? Discuss.

For a gas of particles confined inside a two-dimensional box, the density of states is constant, independent of ε(see Problem 7.28). Investigate the behavior of a gas of noninteracting bosons in a two-dimensional box. You should find that the chemical potential remains significantly less than zero as long as T is significantly greater than zero, and hence that there is no abrupt condensation of particles into the ground state. Explain how you know that this is the case, and describe what does happen to this system as the temperature decreases. What property must ε have in order for there to be an abrupt Bose-Einstein condensation?

In a real hemoglobin molecule, the tendency of oxygen to bind to a heme site increases as the other three heme sites become occupied. To model this effect in a simple way, imagine that a hemoglobin molecule has just two sites, either or both of which can be occupied. This system has four possible states (with only oxygen present). Take the energy of the unoccupied state to be zero, the energies of the two singly occupied states to be -0.55eV, and the energy of the doubly occupied state to be -1.3eV(so the change in energy upon binding the second oxygen is -0.75eV). As in the previous problem, calculate and plot the fraction of occupied sites as a function of the effective partial pressure of oxygen. Compare to the graph from the previous problem (for independent sites). Can you think of why this behavior is preferable for the function of hemoglobin?

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