Module 5 Flashcards
When are two objects in thermal equilibrium?
When there is no net flow of thermal energy between them. Any two objects in thermal equilibrium must be at the same temperature.
What is the zeroth law of thermodynamics?
If two objects are in thermal equilibrium with a third, then all three are in thermal equilibrium with each other.
What does the absolute temperature scale use as its fixed points?
The triple point of water and absolute zero
How do you convert between temperature in Kelvin and degrees centigrade.
T(K)=T(C)+273
What does the kinetic model describe?
How all substances are made up of atoms or molecules, which are arranged differently depending on the phase of the substance.
How are atoms or molecules arranged in a solid?
Regularly arranged and packed closely together, with strong electrostatic forces of attraction between them holding them in fixed positions, but they can vibrate and therefore have kinetic energy.
How are atoms or molecules arranged in a liquid?
Very close together, but they have more kinetic energy than solids, and can change positions and flow past each other.
How are atoms or molecules arranged in gasses?
Have higher kinetic energy than in liquids, and are much further apart. They are free to move past each other as there are negligible electrostatic forces between them, unless they collide with each other or the container walls. They move randomly with different speeds and in different directions.
What is the internal energy of a substance?
The sum of the randomly distributed kinetic and potential energies of atoms or molecules within the substance.
What are the electrostatic potential energies of the atoms or molecules within a gas?
The electrostatic potential energy is zero because there are negligible electrical forces between the atoms or molecules.
What are the electrostatic potential energies of the atoms or molecules within a liquid?
The electrostatic forces between atoms or molecules give the electrostatic potential energy a negative value. The negative means that the energy must be supplied to break the bonds.
What are the electrostatic potential energies of the atoms or molecules within a solid?
The electrostatic forces between atoms or molecules are very large, so the electrostatic potential energy has a large negative value.
What is specific heat capacity?
The energy required per unit mass to change the temperature by 1 K.
What is specific latent heat?
The energy required to change the phase per unit mass while at a constant temperature. When changing from solid to liquid it is the specific latent heat of fusion, and when it is liquid to gas it is the specific latent heat of vaporisation.
How do you calculate the total number of atoms or molecules in a substance?
N = n x NA
N is number of atoms or molecules, n is number of moles, NA is Avogadro’s constant
What are the assumptions made in the kinetic model for an ideal gas?
- the gas contains a very large number of atoms or molecules moving in random directions with random speeds
- the atoms or molecules of the gas occupy a negligible volume compared with the volume of the gas
- the collisions of atoms or molecules with each other and the container walls are perfectly elastic
- the time of collisions between the atoms or molecules is negligible compared to the time between the collisions
- electrostatic forces between atoms or molecules are negligible except during collisions
What is Boyle’s law?
If the temperature and mass of a gas remain constant then the pressure of an ideal gas is inversely proportional to its volume.
What is Charles’ law?
If the volume and mass of a gas remain constant, the pressure of an ideal gas is directly proportional to its absolute temperature.
What is the distribution of particle speeds at different temperatures?
Maxwell-Boltzmann distribution.
The hotter a gas becomes, the greater the range of speeds. The modal speed and r.m.s. speed increase.
What is the Boltzmann constant?
Molar gas constant/Avogadro constant
What is angular velocity?
The rate of change of angle, therefore w = theta/t
w=2pi/T
w=2pif
What is a centripetal force?
Any force that keeps a body moving with a uniform speed along a circular path.
What is centripetal acelleration?
The acceleration of an object travelling in a circular path at a constant speed.
What is simple harmonic motion?
A kind of oscillating motion where the acceleration is given by a=-w^2x where w^2 is a constant for the oscillator.