Simple Models Of Matter

Question 1

What is absoloute zero?

Answer 1

• Lowest possible temp as all patricle have the minimu possible kinetic energy
• -273 degree celcius

Question 2

What causes a change in temp?

Answer 2

A net transfer of thermal energy

Question 3

When two blocks are the same temp theyre in

…..

Answer 3

Thermal equillibrium

Question 4

Specific heat capactiy definition…

Answer 4

Energy needed to raise the temp of 1kg of substance by 1k

Question 5

Method to find soecific heat capacity?

Answer 5

1. equipment: electric heater,thermometer,, with either solid or liquid surrounded by insulating material
2. heat so substance increases 10k
3. attach ammeter and voltemeter to calculate work done (assuming all is transfereed into thermal energy

Question 6

What is boyles law?

Answer 6

At constant temp pressure and volume are inversely proportional

Question 7

How to test boyles law?

Answer 7

1.use a pump, pressure gauge,tube with scale in mm with some oil in
2.The oil traps a pocket of air eith fixed dimentions
.
3. Tyre pump used to increase pressure and recorded by pressure gauge
4.Record volume at every pressire increase
5.multiply should always give ocnstant in ideal gas

Question 8

What is charles law?

Answer 8

At constant pressure volume is directly proportional to temperature

Question 9

How to test charles law?

Answer 9

1. Set up capillary tube w a drop of H2SO4 halfway so theres an air collum at bottom of tube.
2. Stand in near boiling water and measure length of air collum
3. As water cools regularly record length of air collum with temperatures
4. Repeat for average
5. plot length against temp or volume against temp (volume proportional to length) to get straight line through thr origin

Question 10

What is the pressure law?

Answer 10

At constant volume pressure of a gas is directly proportional to temperature

Question 11

Test for pressure law?

Answer 11

1. Immeres flask of air in water and connect to gauge using a tube of negligible volume
   2.Heat the water and stir for uniform temp and allow time to heet air to same temp as water
   3.record temp and pressure from gauge asit cools at regular intervals
   4.repeat
   5plot pressure against temp
2. Can extrapolate to find absoloute zero (temp when pressure is zero)

Question 12

How to find absoloute zero experimentally?

Answer 12

Extropolate pressure against temp graph to find temp when pressure is zero

Question 13

When does the ideal gas equation work well for real gases?

Answer 13

Low pressures ans high temos

Question 14

What are the assumptions made for an ideal gas?

Answer 14

• Particles occupy a ngligible volume compared w volume of the container
• collisions are always perfectically elastic
• negligible forces between particles (except in collidions)
• large no of particles that move rapidly and randomly

Question 15

Explain how to model motion in a gas?

Answer 15

• model by a random walk that assume Each particle starts in one place and moves N steps in random directions to end up spmewhere else
• particles changes direction everytime it collided with another particle
• average distance moved in those steps is modelled by =rootN x length lf one step

Question 16

What is diffusion?

Answer 16

Net movemtn of particles from a high to a low concentration

Question 17

Do ideal gases obey newtons 2nd law?

Answer 17

Yes as the collisions are assumed elastic so momentum is conserved
There fore we can use F=mv/t

Question 18

What does the area under a force time graph show?

Answer 18

Change in momentum/ impulse

Question 19

What is the root mean square speed and why do we use it?

Answer 19

• Particle are travelling in different directions so average v would be zero
• instead we average squared velocities to give mean square soeed and root this number

Question 20

Explain why particle velocity is proportional to pressure in an ideal gas?

Answer 20

• faster particle have greater momentum and therefore greater impules in collisions
• this meams greater forces exerted in collisions Fx change in t=change in p
• and less time between collisions as moving faster
• therefore greater pressure as pressure=force/area

Question 21

Explain why Number of particles is proportional to pressure in an ideal gas?

Answer 21

• More particles means more collisions and every collision excerts a force
• So number of particle proportional to total force and
• Force=pressure/area so greater force grater pressure

Question 22

Explain why the volume of a container is inversely proportional to pressure?

Answer 22

-if volume of comtainer is smaller
Particles collide more often with container and each other as less distance between them so greater change in momentum per secon whuch increases force F=mv/t
-volume smaller so area smaller
-pressure =force/area therfore greater pressure

Question 23

What can u estimate about the dimensions particles are travelling in?

Answer 23

Estimate a third are travelling in one direction at one time

Question 24

Equation to find mean square soeed of particle? What are units?

Answer 24

PV=1/3Nmc^2

P in Pa,V in m^3,N is no of particles,m is kg,c is m^2s^-2

Question 25

What is internal energy?

Answer 25

Sum of kinetic and potential energy of the particles within a system

Question 26

In an ideal gas what can be said about its internal energy

Answer 26

All kinetic-no potential

Question 27

What is internal energy proportional to?

Answer 27

Temperature

As Average energy per particle=kt

Question 28

What equations do you derive E=kT from?

Answer 28

PV=NKT and PV=1/3Nmc^2