M5.1 Thermal Physics Flashcards
what are the fixed points around Kelvin
Absolute Zero
the triple point of water
define brownian motion
the random motion of small particles suspended in a fluid
both direction and speed
describe an experiment to see brownian motion
smoke cell under a microscope using a glass reservoir and a layer of vaseline
smoke should appear to have random motion
air particles knock carbon particles around
air particles too small to see in microscope
why does brownian motion happen
the larger particles suspended collide with the air particles which changes their velocities
proves gasses move freely and randomly
what are the assumptions in brownian motion
Forces between particles are negligible except during collisions
collisions are perfectly elastic
time of collision is negligible
particles occupy a negligible volume
there are lots of particles in random motion
define internal energy
the sum of all the kinetic and potential energy stored in all the particles
define electrostatic potential energy
the energy due to the separation between molecules
what are the factors that affect internal energy
temperature
state of matter
intermolecular forces
define a mole
unit of substanec
1 mole is the amount of particles to make their atomic mass in grams
what is molar mass
mass of one mole of a substance
mass/num of mols
what are the assumptions made in kinetic theory of an ideal gas
molecules of negligible volume
collisions are elastic
cannot be liquified
has no interactions between molecules (except collisions)
obeys te gas laws
boyles law
pressure ∝ 1/V
when temperature is constant
p*v = constant
charles law
V∝T
when pressure is constant
V/t = constant
pressure law
P∝T
p/t = constant
what do the pressure laws combine to make
PV/t =constant
when only one mole that constant is the molar gas constant
PV/t = nR
Pv = nRt
what are the microscopic properties of a gas
mass and speed
what are the macroscopic properties of a gas
pressure and volume
describe the kinetic model of a solid and what happens when heated
particles in a fixed ordered lattice
Vibrate around a fixed point
very small spacing between particles
vibrations amplitue increased when heated
describe the kinetic model of a liquid
have translational kinetic energy
and slide past each other
describe the kinetic model of a gas
particles very far apart
random brownian motion
define potential energy
energy caused by the intermolecular force and the acceleration caused by it
(look at the video notes in the one note)
while heating a substance how do the energies change
when not changing state KE increases much more than PE
When changing state KE constant PE increases lots
how to reduce uncertainty when measring the temperature or calculating the SHC
stir the water regularly to even the temperatures
some energy may be transfered to the container which could be included in calculations
why do we must use the Kelvin scale when in the equation pV = nRT
becuase when p or V tends to 0 T must also tend to 0
Kelvin is the scale where that is 0
aparatus set up to measure pressure against temperature of a gas ina conical flask
how would you ensure results are accurate [4]
turn heat off and stir to ensure heat is evenly distributed
make sure that as much of the conical flaks is immersed in the liquid as possible
the tube is small compared to the volume of the flask
allow time for heat to conduct to the air
why has all the helium particles not escaped the atmosphere over a long period of time [2]
previous about why some helium can escape
helium nucleus is an alpha particle so is “replenished” to the atmosphere through radiation
helium is also found in natural gas deposits underground
figure above is a maxwell boltzman distribution
Use your knowledge to of kinetic theory of gasses to describe the shape of this distribution and explain why some helium is able to escape from earth
random motion and elastic collisions of particles
leads to distribution of KEs among particles
few will have very high velocities at the top end of the distribution
to escape have to be very far from the rms
hence very few will be able to escape
