Thermal Physics Flashcards
What is temperature?
Temperature is the average kinetic energy of the particles in a body.
What is specific heat capacity?
The amount of energy needed to heat 1kg of a substance by 1K.
What is the internal energy of a body?
The internal energy of a body is the sum of all the randomly distributed potential and kinetic energies of all its particles.
What is the Pressure Law?
The Pressure Law states that (for a fixed volume): Pressure/Time = Constant, i.e. p1/t1 = p2/t2 = constant.
What experiment can be conducted to discern the Pressure Law?
A round-bottomed flask contains a constant volume of a gas. It is heated in a water bath whilst connected to a Bourdon pressure gauge. Both the temperature of the gas (assumed to be equal to the temperature of the water bath) and the pressure are recorded and then plotted on a graph of pressure versus temperature. When using Kelvin, this graph is linear and the line passes through the origin, so pressure is directly proportional to temperature.
What is Charles’s Law?
Charles’s Law or the Volume Law states that (for a fixed pressure): Volume/Temperature = Constant, i.e v1/t1 = v2/t2 = constant.
What experiment can be conducted to discern the Volume Law?
A column of air is trapped in an open-ended capillary tube, suspending a bead of mercury. This is heated in a water bath. Since the pressure above and below the bead must be the same, we know that the pressure of the fixed column of gas is atmospheric pressure, and so we can plot a graph of volume versus temperature. Using Kelvin means this graph is linear and passes through the origin, so volume is directly proportional to temperature.
What is Boyle’s Law?
Boyle’s Law states that (for a fixed temperature): Pressure X Volume = Constant, i.e. p1v1 = p2v2 = constant.
What experiment can be conducted to discern Boyle’s Law?
A column of air is trapped above a column of oil. A pump is used to increase the pressure on the oil and as such the pressure on the gas. The volume of trapped air is measured on a scale and the pressure is measured using a pressure gauge. The pressure on the oil is decreased slowly and the data for pressure and volume of the gas is recorded. This must be done slowly and the apparatus must be allowed to stand so that the temperature of the gas can return to room temperature. Plotting a graph of pressure versus 1/volume shows that pressure and volume are inversely proportional (when using Kelvin).
What is the combined gas equation, and what is its drawback?
p1V1/T1 = p2V2/T2 = constant; the drawback is that it can only be used to compare the same gas under different conditions. (T1 and T2 must be in Kelvin).
What is the equation of state?
pV=nRT; where: p is pressure, V is volume, n is number of moles, R is Molar Gas Constant (8.31JK^-1mol^-1), and T is absolute temperature.
What is the relationship between pressure exerted by a gas and the mean speed of the particles?
p=1/3(ϱ)(Crms)^2
What assumptions are made in the derivation of p=1/3(ϱ)(Crms)^2?
P ostulates:
R andom - All gas particles move with random motion; all motions are equally probable.
I dentical - All particles are identical (have the same mass).
V olume - The volume occupied by the particles is negligible compared to the overall volume of the gas.
A ttraction - The force of attraction between particles is negligible.
T ime - The time the particles spend in collisions with the container is negligible compared to time between collisions.
E lastic - All collisions between the particles and the wall are perfectly elastic.
What is the relationship between temperature and KE of a gas?
Total KE of n moles of gas = (n)3/2(RT)
What is the relationship between temperature and KE of one particle in a gas?
Average KE of one particle = 3/2 kT
