thermal physics

Question 1

how do you convert from celsius to kelvin

Answer 1

add 273

Question 2

why is absolute scale used

Answer 2

doesn’t depend of the properties of a given substance

Question 3

what is 0k

Answer 3

absolute zero which means that the particles have minimum internal energy

Question 4

describe the arrangement and energy of particles in a solid

Answer 4

regular arrangement, vibrate around fixed positions

Question 5

describe the arrangement and energy of particles in a liquid

Answer 5

close together, constantly moving past each other

Question 6

describe the arrangement and energy of particles in a gas

Answer 6

spaced very far apart, free to move in all direction

Question 7

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

Answer 7

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

Question 8

what is internal energy

Answer 8

the sum of potential and kinetic energies of a system

Question 9

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

Answer 9

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

Question 10

how can you increase the thermal energy of a system

Answer 10

heat it up or do work on the object

Question 11

explain the energy changes that occur during a change of state

Answer 11

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

Question 12

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

Answer 12

E = mc(delta theta)

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

Question 13

what is specific heat capacity

Answer 13

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

Question 14

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

Answer 14

E = ml

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

Question 15

specific latent heat of a substance

Answer 15

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

Question 16

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

Answer 16

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

Question 17

what is avagadros constant

Answer 17

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

Question 18

what are the key assumptions in the kinetic theory of gasses

Answer 18

• 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

Question 19

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

Answer 19

• 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

Question 20

what is an ideal gas

Answer 20

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

Question 21

what is the ideal gas equation

Answer 21

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

Question 22

what is Boyle’s law

Answer 22

pressure is inversely proportional to volume providing temperature is constant

Question 23

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

Answer 23

they are directly proportional
P/T = constant

Question 24

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

Answer 24

• 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

Question 25

what equation links N, V, p, m and c

Answer 25

pV = 1/3 Nmc^2

N = number of particles
c = mean square speed

Question 26

what is meant by the root mean square speed

Answer 26

the square root of the mean of the squares of the speeds of the molecules

Question 27

what doe the area under a Maxwell boatman curve represent

Answer 27

the total number of particles

Question 28

how does the Maxwell Boltzmann curve change if the temp of a gas is increased

Answer 28

the average particle speed and maximum particle speed both increase and the curve shifts right

the curve becomes lower and more spread out

Question 29

what are the units of the Boltzmann coefficient

Answer 29

j/k

Question 30

the average kinetic energy of a particle in an ideal gas is equal to what

Answer 30

1.5kt

Question 31

true/false : the. internal energy of an ideal gas is proportional to absolute temp

Answer 31

true - as temperature increases the average kinetic energy increases which leads to an increase in internal energy

Question 32

absolute 0

Answer 32

the lowest possible temperature of a system, where no heat remains and the particles in the system have no kinetic energy

Question 33

what is a mole

Answer 33

the amount of substance which contains the same number of particles as atoms ion 12g of carbon 12

Question 34

how to calculate the number of moles

Answer 34

mass/ molar mass

n = m / M

Question 35

how do you calculate the number of particles

Answer 35

number of moles x Na