Ideal Gasses

Question 1

Explain the kinetic theory ( what happens when you increase temperature?)

Answer 1

Increasing temperature increases kinetic energy of the molecules making the molecules move faster therefore there are more frequent collisions with the wars of the container therefore force exerted by each collision increases and change of momentum increases with each collision. Total force is then increased for the same value therefore pressure increases.

Question 2

Name the two equations with pressure and temperature

Answer 2

Pressure= constant x temperature
P1/T1=P2/T2

Question 3

Describe a method that can be used to determine the relationship between pressure and temperature of of gas and how will you analyse the graph to determine a value for absolute zero?

Answer 3

Place a pressure gauge in ice cold water and place this on top of a Bunsen burner
Then check the pressure gauge for zero error and zero reading, then use to measure pressure
Measure the temperature using a thermometer to keep it in the middle of the flask and keep stirring the liquid
Change the temperature by heating the water bath with a Bunsen burner and 5° temperature change record temperature temperature and pressure
Ensure no gas enters or leaves the system
Put a graph of pressure against temperature and extrapolate the best fit line to find the X axis intercept. This will give an experimental value for absolute zero.

Question 4

When does absolute zero happens in gas molecules?

Answer 4

When the gas molecules exert pressure as they will have zero kinetic energy

Question 5

Equation for number of molecules

Answer 5

N= mass/molar mass x avagadros constant)

Question 6

Perfect answer for relation between volume and temp kinetic theory at constant pressure

Answer 6

Increasing the temp will increase the KE of the molecules making them move faster
This leads to an increase the frequency of the collision with the walls of the container
Therfore increased force exerted each collision
To keep pressure constant the volume must increase as this will lower te frequency of the collisions with the surface of the container
The increased force is then spread over a larger area so pressure can be constant
Therfore an increase of temp at a constant pressure requires an increase of volume

Question 7

Give the 2 equations for Charles law

Answer 7

V= kt
V1/t1=v2/t2

Question 8

A balloon shrinks when put into liquid nitrate, it then blow back up when taken out explain why

Answer 8

When a balloon is put into liquid nitrate the temp decreases and mas mass is constant, the number of collisions decreases therfore volume decreases however wen it is taken out temp increase therfore no of collisions increase and volume also increase

Question 9

Explain Charles law experiment

Answer 9

Place a thermometer and tube with an open end into water. The. Open end is to ensure constant pressure.then turn on the Bunsen burner and record readings for temp and volume, by using a vernier calliper to measure the diameter of the tube and see how far the gas travels using the scale for length. Then use the radius for volume. Do this for ultple readings and plot a graph of c against t . T

Question 10

Use Newton laws to explain the pressure of an ideal gas within a cubic box containing N particles each with mass M

Answer 10

The particles of the gas are free to move around with constant random motion and there are no forces of attraction between the particles therefore according to Newton‘s first law they continue to move with a constant velocity until they collide with another particle or the box itself
When a particle collides with a wall of the box the wall will exert an equal and opposite force on the passcode. This is newtons third law.
The size of the fourth exerted by the particle on the wall can be calculated using newtons second law which states that force is equal to the rate of change of momentum for example if a possible queue is travelling directly towards the wall with velocity u its momentum will be mu when it hits the wall. The force of the impact causes it to rebound in the opposite direction at the same speed therefore the momentum is now. -mu therefore the change in momentum is 2mu
Therefore, the force a particle exerts is proportional to its mass and its velocity

Question 11

State gay lussacs law

Answer 11

P=kT
At a constant volume , pressure and absolute temp are directly proportional to the

Question 12

State Charles’s law

Answer 12

V equals constant times temperature therefore the volume of a gas is directly proportional to the absolute temperature of a substance at constant pressure

Question 13

What is an ideal gas

Answer 13

A gas in which the ideal gas laws apply therefore there is no other interactions other than perfectly elastic collisions between the gas molecules

Question 14

What is molar mass?

Answer 14

The mass of one molecule and molar mass is equal to the MR

Question 15

If the equation for Boltzman constant

Answer 15

K=R/Na

Question 16

What is the capital N in the pressure

Answer 16

Number of molecules

Question 17

What is the lowercase N in pressure?

Answer 17

The number of moles

Question 18

A molecule with mass M and initial velocity you collide elastically with a wall use your knowledge of momentum and Newton’s laws to explain why the particle a force on the wall and why this leads to gas pressure

Answer 18

The wall exert a force on the particle so the particle exerts an equal opposite force on the wall the sum of the forces from an particles divided by the area equals pressure therefore there is gas pressure

Question 19

Why is there no potential energy in an ideal gas?

Answer 19

As molecules exert no force on each other except during collisions therefore internal energy equals to the kinetic energy of the particles

Question 20

Two gases of different particles are at the same temperature if one of the gases have a larger mass will it have a higher kinetic energy?

Answer 20

No Isaiah at the same temperature, therefore they were both have the same kinetic energy

Question 21

Defined the internal energy of an ideal gas

Answer 21

The sum of the main kinetic energies of the particles and there is zero potential energy in the ideal gas

Question 22

State in words, Boyles law

Answer 22

For a fixed mass of gas at a constant temperature pressure is inversely proportional to volume

Question 23

Explain Boyles law in terms of the kinetic theory of gases

Answer 23

When gas is a constant temperature, it’s pressure can be decreased by increasing its volume
This is because in a larger volume the molecules of gas will have to travel further between collisions with the wars on the container therefore there are fewer collisions per second. This means pressure decreases.

Question 24

Explain how newtons law are used in the derivation of the equation PV=1/3Nmc^2

Answer 24

Newton’s first law tells us that the gas molecule will move in a straight line until it collides with the walls of the container
Newton second law helps us find the force on the molecule caused by its collisions with the wall of the container as force is equal to the rate of change of moment
Newton’s third Lord tells us that the force wall is equal opposite the force exerted on the molecule

Question 25

State 6 assumptions of an ideal gas

Answer 25

Volume of the molecules is negligibly smaller compared to the volume of the gas
Molecules have perfectly elastic collisions
There is a large number of molecules
Molecules move in a random linear motion
The time between collisions is much larger than the duration of the collisions
There are no intermolecular forces

Question 26

State the general characteristics of the Maxwell Boltzman distribution curve

Answer 26

The area under the curve represents the total number of particles and this stays the same what ever the temperature
As temperature decreases the peak of the curve will shift further to the left

Question 27

A. Student investigates Brownian motion by observing through a microscope smoke particles suspended in air. Describe the behaviour of the particles and how the observations led to conclusions about the nature and properties of the gas molecules

Answer 27

Smoke particles move in a random zigzag manner
This is due to the random linear motion of the air particles as they are hitting the smoke particles, and there is small movement of smoke particles as they are being hit from all directions due to the large numbers of air molecules
The smoke particles are visible but the air particles are not therfore they are extremely small
The smoke particles are continuously moving as the air molecules are continuously moving.

Question 28

Use kinetic theory of gases to explain why the pressure of an ideal gas increases when heatead at constant volume

Answer 28

Particles are moving faster so there are more collisions per second with the wall, therefore more momentum change per second, therfore each collision has a greater momentum change so force is greater

Question 29

Explain why the volume occupied by an ideal gas increases when it is heated at a constant pressure

Answer 29

More collisions per second, this increases pressure
To keep the same a greater volume is required as there are fewer collisions per second

Question 30

4 assumptions about an ideal gas properties and behaviour when deriving an expression for the pressure of an ideal gas

Answer 30

All collisions are elastic
Molecules have negiligable volume compared to the volume of the gas
Time of collisions is much less than time in between collisions
No forces in between molecules

Question 31

The smoke particles in the Brownian motion are observed to move why

Answer 31

They are colliding with the air molecules

Question 32

Explain why some of the rms speeds of the particles are less than the average mean speed

Answer 32

There is a range of speeds
Some molecules will have lower speeds than the mean

Question 33

Stay and explain a situation in which the very high value for specific heat capacity for water is useful

Answer 33

Car cooling systems because it absorbs large amount of heat for small rising temp

Question 34

internal energy changes when a mass of water at 100°C becomes an equal mass of vapour at 100°C? Explain why

Answer 34

The potential energy of the molecules is increasing however the kinetic energy of the molecules is the same for water and the steam as they have the same temperature therefore work is done in moving particles apart therefore internal energy increases

Question 35

The molar mass of hydrogen is 2.02x10^-3 calculate the mass of a hydrogen molecule

Answer 35

Mol=mass/mr
Therefore N/NA=mass/mr
N=1
Therefor mass= 2.02x10^-3/NA