thermal physics Flashcards
how do you convert from celsius to kelvin
add 273
why is absolute scale used
doesn’t depend of the properties of a given substance
what is 0k
absolute zero which means that the particles have minimum internal energy
describe the arrangement and energy of particles in a solid
regular arrangement, vibrate around fixed positions
describe the arrangement and energy of particles in a liquid
close together, constantly moving past each other
describe the arrangement and energy of particles in a gas
spaced very far apart, free to move in all direction
how does brownian motion give evidence for the particle model of matter
smoke particles suspend in air can be seen to move randomly in all directions. this must be as a result of random collisions with particles making up the air
what is internal energy
the sum of potential and kinetic energies of a system
true or false: at a given temp all particles in a material have the same kinetic energy
false. the kinetic energies will be randomly distributed around a central most likely about
how can you increase the thermal energy of a system
heat it up or do work on the object
explain the energy changes that occur during a change of state
the potential engird of the particles change but the kinetic energies don’t - this is the flat part of a graph
what equation can be used to determine the energy required to change the temp of a substance
E = mc(delta theta)
E = energy
m = mass
C = specific heat capacity
delta theta = temp change
what is specific heat capacity
the energy required to raise the temp of 1kg of a substance by 1k
give the equation to work of the energy for change of state
E = ml
m = mass
l = specific latent heat of fusion or vaporisation
specific latent heat of a substance
the energy required to change the state per unit mass of a substance while keeping the temp constant
in an experiment to find c for water lots of energy input escapes to the surrounding. will this lead to an over or underestimate of specific heat capacity
an overestimate
- specific heat capacity = E/m(change in temp)
- the energy input will be used, but the temp change of the water will be lower that it should be due to the escaped energy therefore c will be too high
what is avagadros constant
the number of atoms there are in one mole of a substance
what are the key assumptions in the kinetic theory of gasses
- large number of molecules in random rapid motion
- particles are negligibly small compared to the total volume of the gas
- all collisions are perfectly elastic
- time taken for collisions is perfectly negligible small compared with the time between collisions
- between collisions there are no forces between particles
why do gases exert a pressure on the container they are in
- gas particles collide with the surfaces of the container
- the container exerts a force on the particles to change their direction
- particle exert an equal and opposite force on the container
- pressure is force applied in total by all particles per unit area
what is an ideal gas
a gas where the molecules don’t interact with each other
the molecules are thought to be perfect spheres
what is the ideal gas equation
pV = nRT
n= number of moles
R = ideal gas constant
T = absolute temperature
what is Boyle’s law
pressure is inversely proportional to volume providing temperature is constant
assuming constant volume, how are the pressure and temperature of a gas related
they are directly proportional
P/T = constant
use the kinetic theory of gases to explain why temperture increase leads to an increase in pressure
- temp increase means the particles have more kinetic energy
- more kinetic energy means greater change in momentum during collisions with the container. there are also more frequent collisions
- change in momentum is proportional to force applied and therefore to pressure as well
what equation links N, V, p, m and c
pV = 1/3 Nmc^2
N = number of particles
c = mean square speed
what is meant by the root mean square speed
the square root of the mean of the squares of the speeds of the molecules
what doe the area under a Maxwell boatman curve represent
the total number of particles
how does the Maxwell Boltzmann curve change if the temp of a gas is increased
the average particle speed and maximum particle speed both increase and the curve shifts right
the curve becomes lower and more spread out
what are the units of the Boltzmann coefficient
j/k
the average kinetic energy of a particle in an ideal gas is equal to what
1.5kt
true/false : the. internal energy of an ideal gas is proportional to absolute temp
true - as temperature increases the average kinetic energy increases which leads to an increase in internal energy
absolute 0
the lowest possible temperature of a system, where no heat remains and the particles in the system have no kinetic energy
what is a mole
the amount of substance which contains the same number of particles as atoms ion 12g of carbon 12
how to calculate the number of moles
mass/ molar mass
n = m / M
how do you calculate the number of particles
number of moles x Na
