thermal Flashcards
define internal energy
the sum of randomly distributed potential and kinetic energies of the particles in a body
how does the internal energy of the system increase
-heat energy is transferred
-work is done on the system
equation of first law of thermodynamics
Q=change in U+W
U=internal energy
W=work done by the system
Q=heat added
define specific heat capacity
the amount of energy required to increase the temperature of 1 kg of the substance by 1C without changing its state
define specific latent heat of fusion/vaporisation
energy required to change the state of 1 kg of the substance from _ to _ without changing its temperature
how to calculate delta theta
final temperature - initial temperature
what cancels out in the continuous flow calorimeter calculation
heat loss, as in this experiment delta theta is set to be constant so heat loss is also constant
explain why an electric motor become warm when it is used
-work is done by the magnetic field
-electrons collides and gives up some of their energy in the wire
describe the energy transfer in the electric motor
-electrical energy converted to kinetic energy and heat energy in the motor,
-heat energy transferred to the surrounding from the motor
what is absolute zero temperature
0K,=-273C
what is Boyle’s law
p1V1=p2V2, constant temperature
what is Pressure’s law
p1/T1=p2/T2
what is Charles’s law
V1/T1=V2/T2
the steeper the gradient in volume against temperature graph means that
the lower the pressure
the further the curve away from the origin in pressure against volume graph
the higher the temperature
difference between n and N
n=moles , N=number of molecules, N=Avogadro*n
equation for work done
W=p*change in V
define Avogadro’s constant
the number of molecules in one mole of a substance/ the number of atoms in 12g of carbon-12
For ideal gas, all molecules of a gas are identical so they have the same
mass and change in momentum on average
describe the motion of ideal gas
molecules move in random motion
How do ideal gas collide
elastic collision, KE is conserved
How does it mean when ideal gas said to be following the newton’s 1st law
the molecules move in straight
assumption on the volume for ideal gas
the volume of molecules is negligible compared to the volume of the gas
large amount of molecules for ideal gas so
constant force on the wall
what can we say about the attraction between molecules in ideal gas
no attraction so potential energy is zero
assumption on time for ideal gas
the duration of collisions is negligible compared to the time between each collisions
how to derive pV=1/3Nm(c rms)^2
-change in momentum for each molecules
-one round trip in t time
-times them to get the total change in momentum of one molecule
-divide the total N by 3 as molecules move in random motion
-time it by the total change in momentum
-find F , F=mv/t
-find p, substitute in V
equation for total kinetic energy of molecule in ideal gas
KE=3/2nRT
methodology for answering KE model explanation
-effects on collisions per second/mean KE due to___
- effects on change in momentum and rate of change in momentum
-force is proportional to pressure
