thurmal physics (everything)

Question 1

the higher the tempreture of a body the higher the…

Answer 1

avarge Ek of particals

Question 2

what is the internal enegy of a body

Answer 2

Ek + potential enegy

Question 3

what is a closed system…

this means that…

(need to be dubble checked)

Answer 3

a system wich does not allow transfer of enegy and mass in or out

total enegy is constent and there is no work done unless the body is heated or cooled

Question 4

enegy is ______ ______ between particals within a system, through _______ ________ _______ but the _____ _______ ______ of all the particals ______ _____ duroing these collisions

Answer 4

constantly transfered, collisions between particals, total combined enegy, doesnt change

Question 5

how can internal enegy be incresed

Answer 5

• by heating
  OR
• by doing work to transfer enegy to the system (e.g changing shape)

Question 6

how can internal enegy be reduced

Answer 6

-by cooling
OR
-by doing work to remove enegy from the system

Question 7

a change of state causes a…

internal enegy increases as a result of change in state:
- what changes to cause an increase in internal enegy
- what stays constent

this means…

Answer 7

change of potential energy

potential enegy of the particals is changed
while
Ek is constent

tempreture stays constent

Question 8

specific heat capacity (c) is…

Answer 8

the amount of enegy needed to raise the tempreture of 1kg of a substanse by 1k (or1c’)

Question 9

give enegy change equaition
(When dealing with c)

Answer 9

ΔQ=mcΔT
enegy change = mass x spesific heat capacity x change in tempreture

(Δθ or Δt is sometimes used intead of ΔT)

Question 10

specific latent heat is…

therefore
the spesific latent heat (L) of _____ or ______ is the quantity of ______ ______ required to ______ ___ _____ of __ of a substance

Answer 10

the enegy needed to to brake the bonds that hold particals together therefore changing its state
(note you have to say some bonds if it is not a gass as there is still some bonds there)

fusion, vaoration, thurmal enegy, change the state, 1Kg

Question 11

give the energy change equation
(for l)

Answer 11

ΔQ=ml
enegy change = mass of substance changed x specific latent heat

Question 12

0K is where all particals have the _____ possible __

E of particals ∝

Answer 12

minumim, Ek

E of particals ∝tempreture

Question 13

K (kelvin) =

Answer 13

K = C + 273

Question 14

boyles law:
give equation

Explain

draw the graph

Answer 14

p∝1/V when T is constent

• if you reduce the volume of a gass the particals will be closer together
• therefore the particals will collid with each other and the container more often, so the pressure will increase

see pg 110

Question 15

charles law:
equation

explain

draw the graph

Answer 15

V∝T when p is constent

• when you heat a gass the particals gain Ek.
• this means the particals move quicker and further apart
• therefore to keep constent pressure the gasses volume must increase
  see pg 110

Question 16

pressure law:
give equation

explain

draw graph

Answer 16

P∝T when V is constent

• if you increase the tempreture of a gass the particals within the gass will have a greater Ek
• this means the particals will move faster
• if volume is constent then the particals will collide with each other and the conainer more often
• thereofre increaseing the pressure

see pg 110

Question 17

charles law, boyles law and the pressure law all apply if the gass is…

Answer 17

ideal

Question 18

define temperature when dealing with gases

Answer 18

This is the measure of the average Ek of the particles

Question 19

what does 1 mole contain

what is the mass of 1 mole of (4)(2)He

nomber of moles is represented as… and avagardos constent is represented as… and nomber of melecules is represented as…

therefore
nomber of molecules is given by the queation…

Answer 19

6.02x10^23 (avagardos constent N(A) - wich is number of atoms in a mole)

4g (1 mole is = to the reletive mass x 1g)

n, N(A), N

N=nN(A)

Question 20

what is R and give its value

Answer 20

gas constent for 1 mole of gas
(8.31Jmol^-1K^-1)

Question 21

give the ideal gas equation

when does this equation work well

Answer 21

pV=nRT

for when a real gass aproximats to a ideal gas.
this is when:
- low pressure
- high tempretures (compeared to there boiling point)

Question 22

what is K (not kelvin)…

K also =

when does this work

Answer 22

gas constent for 1 partical
(1.38x10^-23JK^-1)
(boltzmanns constent)

K=R/N(A)

when dealing with large nombers of molecules
because K is a statistical avarge for 1 partical

Question 23

give the equation of state equation

derive it

Answer 23

pV=NKT

pV=nRT
N=nN(A) K=R/N(A)
N/n=R/k
NK=nR
pV=NKT

Question 24

work is done to change the _____ of gass at a constent ________.

this normaly involves transfer of….

give wd equations (not given)

draw graph of p/V, what is the area

Answer 24

volume, tempreture

heat

wd=pΔV

see pg 113, area=wd

Question 25

give kenetic theory model equation and dirive it

Answer 25

pV=1/3 x Nm(Crms)^2 see phone or pg 114

Question 26

list all 5 assumption that are used in kinetic theory what is the gas that obays these assumptions called?

Answer 26

1. the molecules continually move about randomly 2. the motion of the molecules follow Newton's laws 3. Collisions between molecules themselfs or at the walls of a container are perfectly elastic 4. exept for during collisions, the molecules always move in stright lines 5. any forces that act during collisions last for much less time than the time between collisions an ideal gas

Question 27

ideal gases have internal enegys that are dependent only on... meaning...

Answer 27

kenetic enegy of the particals within the body the potential enegy = 0J

Question 28

when do real gases act like ideal gases

Answer 28

when: - low pressure - tempreture is high (compeared to there boiling point)

Question 29

what is the 2 approximation for the kinetic enegy of the molecules in any substance equation dirive both

Answer 29

Ek=3/2 x KT Ek=3/2 x RT/N(A) pV=1/3 x Nm(Crms)^2 pV= nRT pV=pV 1/3 x Nm(Crms)^2 = nRT 1/2 x Nm(Crms)^2 = 2/3 x nRT 1/2 x m(Crms)^2 = 2/3 x nRT/N NK = nR 1/2 x m(Crms)^2 = 2/3 x NkT/N 1/2 x m(Crms)^2 = 2/3 x kT therefore Ek=2/3 x kT K=R/N(A) 1/2 x m(Crms)^2 = 2/3 RT/N(A) therefore Ek=2/3 RT/N(A)

Question 30

emam question (2mark) Tempreture is constent but pressure in oven decreases as atoms leave through an exit whole. explain, using kinetic theory, why the pressure decreases

Answer 30

- because the nomber of particals within the oven decreases, the possible number of collisions per second also decreases. - as the change in p experienced by a partical when colliding with the container is constent (u, speed is content) then the total Δp per second experienced by teh container will decrease thereofre presure drops