Flashcards on Thermal Physics

Define Internal energy (U)

The sum of the kinetic and potential energies of the molecules of a system.

What is Absolute zero?

The temperature at which the internal energy of a system is at a minimum, corresponding to pV = 0 for a gas.

What is Heat flow?

The transfer of heat energy from a region of higher temperature to a region of lower temperature.

What does the term “Thermal equilibrium” mean?

A state where the temperature is the same on both sides of a boundary, resulting in no heat flow.

First law of thermodynamics

States that the increase in internal energy (ΔU) of a system is given by ΔU = Q - W,

where Q is heat entering the system and

W is work done by the system.

What is Isothermal expansion?

A process where a gas expands slowly at constant temperature, resulting in ΔU = 0 and Q = W.

Define Work (W)

Energy transferred by doing work on a system, calculated as W = FΔx or W = pΔV.

What is the Specific heat capacity (c)?

The heat required per kilogram, per degree Celsius or Kelvin, to raise the temperature of a substance.

What is referred as the Change in internal energy (ΔU)?

The difference in internal energy of a system, calculated as ΔU = Q for solids and liquids where volume change is negligible.

What does a p-V graph show?

A graphical representation used to calculate work done in a system by finding the area under the curve.

What is the Molar gas constant (R)?

A constant used in equations involving gases, relating to the number of moles.

R = 8.31 Jmol^-1 K^-1

What is the Boltzmann constant (k)?

A physical constant that relates the average kinetic energy of particles in a gas with the temperature of the gas.

k = 1.38 × 10^-23 JK^-1

Change in volume (ΔV)

The difference in volume of a gas, used in calculating work done on or by the system.

Explain why the change in internal energy over a closed cycle is zero

Since the system returns to its original state, the total heat and work done over the cycle balance out, resulting in:

U = Q - W = 0

Thus, the change in internal energy over a closed cycle is zero.