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Random Motion and Kinetic Theory

Understand the impact of temperature on energy states & molecular interactions in gases and liquids through engaging physics questions.

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Random Motion and Kinetic Theory

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  1. Random Motion and Kinetic Theory

  2. In the Boltzmann factor, , the "T" means: • Higher-energy states are only possible above a certain temperature • Higher-energy states are only possible below a certain temperature • Higher-energy states become more probable as the temperature increases • Higher-energy states become more probable as the temperature decreases • More than one of these • None of these NEXUS/Physics Clicker Questions

  3. A gas of molecules at room temperature interacts with the potential shown below. Each molecule can be in the state E1 or E2. If the gas is at STP and E1 – E2 = 25 meV, at equilibrium, the number of molecules found in the state E1divided by the number of molecules found in the state E2 will be • About 1 • About 1/3 • About 3 • Much, much larger than 1 • Much, much smaller than 1 • Cannot be determined from the information given. NEXUS/Physics Clicker Questions

  4. The energy of a C-C single bond is about 350 kJ/mol. What is the probability that thermal motion will result in breaking this bond?What if it were a double C=C bond? (Energy about 615 kJ/mol) NEXUS/Physics Clicker Questions

  5. The molecules in liquid water are connected by hydrogen bonds whose energy is about 23 kJ/mol. (This is what is responsible for the heat of vaporization of water.) What is the probability that the thermal motion of the water molecules at STP will result in breaking one of those hydrogen bonds? NEXUS/Physics Clicker Questions

  6. If we assume that the atmosphere is in thermal equilibrium and at a uniform temperature (not really a great assumption!), then we expect the density of a given molecule in the atmosphere (say oxygen) to fall off with height by the Boltzmann factor (this defines h0). Find h0, given that at STP, kBT≈ 1/40 eV or RT ≈ 2.4 kJ/mole and 1 eV/molecule ~ 100 kJ/mole. NEXUS/Physics Clicker Questions

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