Chapter 14, 15 - Thermal Physics Flashcards
What are the 3 states of matter and their properties?
Solid - Particle vibrate in a fixed position in a regular lattice, there is a strong force of attraction between atoms.
Liquid - Particle are constantly moving and can flow over each other, but still a force of attraction between atoms.
Gas - Particles are free to move, little to no force of attraction between the atoms.
What is Brownian Motion?
Brownian motion is the random movement of atoms. This can be observed by pollen on water.
What is internal energy?
Internal energy is the sum of the kinetic and the potential energy of particle within a system.
What happens to internal energy at at change in phase?
At a change in state the temperature of a substance remains the same, however the atoms have an increased potential energy as the force of attraction between the atoms is being weakened.
How do you convert to Kelvin from degrees Celsius?
Celsius + 273 = Kelvin
What is specific heat capacity?
The specific heat capacity of a substance is defined as the the energy required per unit of mass to raise the temperature by 1 Kelvin.
E = mc∆𝜃
How can specific heat capacity be experimentally determined?
A known mass of substance is heated using an electric heater. The voltage, current, time and temperature rise is recorded.
VIt = mc∆𝜃
What is specific latent heat?
Energy is required in order for a substance to change phase.
E = mL
What is specific latent heat of fusion?
The specific latent heat of fusion, Lf, is the energy required per unit mass to change the phase of a substance from solid to liquid.
What is specific latent heat of vaporisation?
The specific latent heat of vaporisation, Lv, is the energy required per unit mass to change the phase of a substance from liquid to gas.
What are moles?
Moles are the SI unit for the amount of a substance.
1 mole contains 6.02 x 10^23 (Avogadro’s Constant).
n = m/M
What are the assumptions made to model a gas as an ideal gas?
The gas contains a large number of atoms which move with random, rapid motion.
The volume of the gas atoms is negligible when compared to the total volume of the gas.
All collisions between atoms, with other atoms and the walls of the container, are perfectly elastic.
The time taken for atoms to collide is negligible compared to the time between collisions.
The electrostatic forces between the atoms are negligible, except when the atoms are colliding.
How is Pressure explained by Ideal Gas Laws?
As collisions are perfectly elastic, rebound speed is equal to impact speed. Change in momentum is 2mv.
As p = Ft, F = 2mv/t
Using Newton’s 3rd law, we can stay force exerted on the is equal to the force multiplied by the atoms in that that area.
What is Boyle’s Law?
For a fixed mass of gas at constant temperature, the pressure is inversely proportional to the volume.
k = pV
What is Charles’ Law?
For a fixed mass of gas at a constant volume, the pressure is proportional to temperature.
p/T = k
What is the ideal gas equation relating Boyle’s and Charles’ Laws?
pV = nRT
p(pa)
V(m^3)
n(mol)
R(8.31)
T(k)
How can you investigate Boyle’s Law?
A sealed syringe can be filled with gas and connected to a pressure gauge.
The Syringe can be used to vary the volume.
Volumes and Pressure recorded.
Graph of pressure against 1/volume will give a straight line.
How can absolute zero be investigated?
A sealed container of air is connected to a pressure gauge.
Place container into a water bath, and take pressure reading at different temperatures.
Plot a graph of pressure again temperature, producing a straight line.
Extrapolate graph to 0 pa, this is the estimated value of 0 kelvin.
What is root mean square speed?
Root mean square speed, c̄, is found by averaging the squares of individual speeds and then rooting it.
What is the equation for pV on a microscopic scale using c̄?
pV = ⅓Nmc̄²
Where N is the number of molecules
m is the mass of an individual molecule
How does the speed of molecules vary?
The Maxwell-Boltzmann distribution shows how molecular speed varies in abundance.
The hotter a substance, the further the peak is to the right and the broader the peak.
What is the Boltzmann Constant?
k = R/Nₐ = 8.31/6.02x10²³ = 1.38x10⁻²³
pV = nRT → pV = NkT
What is the relation between kinetic energy and temperature in ideal gases?
Kinetic energy is proportional to the temperature.
pV=Nkt and pV=⅓Nmc̄²
kt = ⅓mc̄²
³/₂kt = ½mc̄²
³/₂kt = Eₖ
What is the internal energy of an ideal gas?
In an ideal gas the potential energy is equal to the kinetic energy. This is because we assume there are no electrostatic force, therefore no potential energy.
