thermal physics Flashcards

1
Q

how do you convert from celsius to kelvin

A

add 273

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2
Q

why is absolute scale used

A

doesn’t depend of the properties of a given substance

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3
Q

what is 0k

A

absolute zero which means that the particles have minimum internal energy

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4
Q

describe the arrangement and energy of particles in a solid

A

regular arrangement, vibrate around fixed positions

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5
Q

describe the arrangement and energy of particles in a liquid

A

close together, constantly moving past each other

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6
Q

describe the arrangement and energy of particles in a gas

A

spaced very far apart, free to move in all direction

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7
Q

how does brownian motion give evidence for the particle model of matter

A

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

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8
Q

what is internal energy

A

the sum of potential and kinetic energies of a system

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9
Q

true or false: at a given temp all particles in a material have the same kinetic energy

A

false. the kinetic energies will be randomly distributed around a central most likely about

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10
Q

how can you increase the thermal energy of a system

A

heat it up or do work on the object

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11
Q

explain the energy changes that occur during a change of state

A

the potential engird of the particles change but the kinetic energies don’t - this is the flat part of a graph

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12
Q

what equation can be used to determine the energy required to change the temp of a substance

A

E = mc(delta theta)

E = energy
m = mass
C = specific heat capacity
delta theta = temp change

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13
Q

what is specific heat capacity

A

the energy required to raise the temp of 1kg of a substance by 1k

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14
Q

give the equation to work of the energy for change of state

A

E = ml

m = mass
l = specific latent heat of fusion or vaporisation

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15
Q

specific latent heat of a substance

A

the energy required to change the state per unit mass of a substance while keeping the temp constant

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16
Q

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

A

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

17
Q

what is avagadros constant

A

the number of atoms there are in one mole of a substance

18
Q

what are the key assumptions in the kinetic theory of gasses

A
  • 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
19
Q

why do gases exert a pressure on the container they are in

A
  • 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
20
Q

what is an ideal gas

A

a gas where the molecules don’t interact with each other
the molecules are thought to be perfect spheres

21
Q

what is the ideal gas equation

A

pV = nRT
n= number of moles
R = ideal gas constant
T = absolute temperature

22
Q

what is Boyle’s law

A

pressure is inversely proportional to volume providing temperature is constant

23
Q

assuming constant volume, how are the pressure and temperature of a gas related

A

they are directly proportional
P/T = constant

24
Q

use the kinetic theory of gases to explain why temperture increase leads to an increase in pressure

A
  • 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
25
what equation links N, V, p, m and c
pV = 1/3 Nmc^2 N = number of particles c = mean square speed
26
what is meant by the root mean square speed
the square root of the mean of the squares of the speeds of the molecules
27
what doe the area under a Maxwell boatman curve represent
the total number of particles
28
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
29
what are the units of the Boltzmann coefficient
j/k
30
the average kinetic energy of a particle in an ideal gas is equal to what
1.5kt
31
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
32
absolute 0
the lowest possible temperature of a system, where no heat remains and the particles in the system have no kinetic energy
33
what is a mole
the amount of substance which contains the same number of particles as atoms ion 12g of carbon 12
34
how to calculate the number of moles
mass/ molar mass n = m / M
35
how do you calculate the number of particles
number of moles x Na
36