OCR A Physics A-level: Thermal Physics

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What is the force exerted by the wall on the atom, according to Newton's third law?

Equal and opposite force to the force exerted by the atom on the wall.

What is the relationship between pressure and volume at constant temperature, according to Boyle's law?

Pressure is inversely proportional to volume.

What is the constant of proportionality in the equation pV = nRT?

The molar gas constant, R.

What is the purpose of lowering the syringe slowly in the experiment to investigate Boyle's law?

To prevent heat from being produced from friction. Signup and view all the answers

What is the relationship between pressure and temperature at constant volume, according to Charles' law?

Pressure is directly proportional to temperature. Signup and view all the answers

What is the unit of measurement for the molar gas constant, R?

Jmol-1K-1. Signup and view all the answers

What is the purpose of plotting pressure against 1/volume in the experiment to investigate Boyle's law?

To show a constant relationship and verify Boyle's law. Signup and view all the answers

What is the goal of the experiment to estimate absolute zero using gas?

To determine the value of absolute zero in °C. Signup and view all the answers

What is the equation that combines Boyle's law and Charles' law?

pV = nRT. Signup and view all the answers

What is the result of collisions between molecules in a gas?

Molecules travel with random speed and direction. Signup and view all the answers

What is the electrostatic attraction between molecules in a gas?

Negligible. Signup and view all the answers

What is the definition of internal energy?

The sum of randomly distributed kinetic and potential energies associated with the atoms or molecules of a substance. Signup and view all the answers

What happens to the kinetic energy of molecules when a substance is heated but remains in the same state?

It increases. Signup and view all the answers

What happens to the potential energy of molecules when a substance changes state?

It increases. Signup and view all the answers

What is the definition of absolute zero?

The point where all molecules in a substance stop moving completely, which is 0K. Signup and view all the answers

What is the specific heat capacity of a substance?

The energy required per unit mass to increase the temperature by 1K. Signup and view all the answers

What is the equation for specific heat capacity?

E = mc∆θ Signup and view all the answers

What are the units of specific heat capacity?

Jkg-1K-1. Signup and view all the answers

What is the temperature at which the melting point of pure ice is marked on the Celsius scale?

0°C Signup and view all the answers

What is the temperature at which the boiling point of water is marked on the Celsius scale, under atmospheric pressure?

100°C Signup and view all the answers

What is the triple point of pure water used as a fixed point in the thermodynamic scale of temperature?

273.16K Signup and view all the answers

What is the relationship between the temperature increase in Kelvin and Celsius?

A temperature increase of 1 kelvin is equal to an increase of 1 Celsius. Signup and view all the answers

What happens when two substances are in contact, and one is hotter than the other?

There will be a net flow of thermal energy from the hotter object to the cooler object. Signup and view all the answers

What is the state of two objects when there is no net transfer of thermal energy between them?

They are in thermal equilibrium. Signup and view all the answers

What is the main difference between the kinetic energy of molecules in solids, liquids, and gases?

The kinetic energy of molecules increases as the phase changes from solid to liquid to gas. Signup and view all the answers

What is the difference between the electrostatic attraction between molecules in solids, liquids, and gases?

The electrostatic attraction between molecules decreases as the phase changes from solid to liquid to gas. Signup and view all the answers

What type of collision occurs between molecules in the gaseous phase?

Elastic collisions Signup and view all the answers

What is the relationship between the kinetic energy of gas molecules and the pressure of the gas?

As the kinetic energy of gas molecules increases, the pressure of the gas also increases. Signup and view all the answers

What is the significance of the x-intercept in a graph of pressure against temperature?

The x-intercept represents absolute zero, where the gas molecules have no kinetic energy and therefore no pressure. Signup and view all the answers

What is the root mean square (r.m.s.) speed of gas molecules, and how is it related to the pressure of the gas?

The r.m.s. speed is the square root of the average of the squares of the individual velocities of the molecules, and it is directly proportional to the pressure of the gas. Signup and view all the answers

How does the Maxwell-Boltzmann distribution change as the temperature of the gas increases?

The peak of the graph shifts to a higher speed, and the distribution becomes more spread out. Signup and view all the answers

What is the relationship between the Boltzmann constant (k) and the molar gas constant (R)?

The Boltzmann constant (k) is equal to the molar gas constant (R) divided by Avogadro's Constant (NA). Signup and view all the answers

What is the equation that relates the pressure of a gas to its root mean square speed?

p = ⅓(Nm/V)c^2, where p is the pressure, N is the number of molecules, m is the mass of a single molecule, V is the volume, and c is the root mean square speed. Signup and view all the answers

What is the significance of absolute zero in the context of gas behavior?

At absolute zero, the gas molecules have no kinetic energy and therefore no pressure. Signup and view all the answers

How does the Maxwell-Boltzmann distribution show the behavior of gas molecules?

The distribution shows the number of molecules with each speed, with the area under the graph representing the total number of molecules. Signup and view all the answers

What is the advantage of using the Boltzmann constant (k) in deriving an equation for the state of an ideal gas?

It allows for the derivation of a second equation, pV = NkT, which is equivalent to the ideal gas law, pV = nRT. Signup and view all the answers

What is the physical significance of the Boltzmann constant (k) in the context of an ideal gas?

The Boltzmann constant (k) relates the temperature of an ideal gas to the kinetic energy of its molecules. Signup and view all the answers

Explain why the kinetic energy of gas molecules is proportional to the temperature of an ideal gas.

The kinetic energy of gas molecules is proportional to the temperature of an ideal gas because the temperature of an ideal gas is a measure of the average kinetic energy of its molecules. Signup and view all the answers

Derive the equation for the internal energy of an ideal gas, assuming that the potential energy of the gas molecules is negligible.

The internal energy (U) of an ideal gas is equal to the total kinetic energy of its molecules, i.e., U = 3/2nRT, where n is the number of moles of gas and R is the gas constant. Signup and view all the answers

What is the physical meaning of the mean kinetic energy of gas molecules in an ideal gas?

The mean kinetic energy of gas molecules in an ideal gas represents the average kinetic energy of the molecules, which is proportional to the temperature of the gas. Signup and view all the answers

Explain how the kinetic energy of gas molecules is related to their root-mean-square (r.m.s.) speed.

The kinetic energy of gas molecules is proportional to the square of their r.m.s. speed. Signup and view all the answers

Derive the equation that relates the Boltzmann constant (k) to the gas constant (R) and the Avogadro constant (NA).

The equation is k = R/NA, which relates the Boltzmann constant to the gas constant and the Avogadro constant. Signup and view all the answers

What is the significance of the assumption that there are no electrostatic forces between molecules in an ideal gas?

The assumption that there are no electrostatic forces between molecules in an ideal gas implies that the potential energy of the gas molecules is negligible. Signup and view all the answers

Explain why the internal energy of an ideal gas is proportional to its temperature.

The internal energy of an ideal gas is proportional to its temperature because the kinetic energy of the gas molecules is proportional to the temperature. Signup and view all the answers

Derive the equation that relates the mean kinetic energy of gas molecules to the Boltzmann constant (k) and the temperature (T) of an ideal gas.

The equation is Ek = 3/2kT, which relates the mean kinetic energy of gas molecules to the Boltzmann constant and the temperature of an ideal gas. Signup and view all the answers