Ideal Gasses Flashcards
Explain the kinetic theory ( what happens when you increase temperature?)
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.
Name the two equations with pressure and temperature
Pressure= constant x temperature
P1/T1=P2/T2
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?
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.
When does absolute zero happens in gas molecules?
When the gas molecules exert pressure as they will have zero kinetic energy
Equation for number of molecules
N= mass/molar mass x avagadros constant)
Perfect answer for relation between volume and temp kinetic theory at constant pressure
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
Give the 2 equations for Charles law
V= kt
V1/t1=v2/t2
A balloon shrinks when put into liquid nitrate, it then blow back up when taken out explain why
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
Explain Charles law experiment
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
Use Newton laws to explain the pressure of an ideal gas within a cubic box containing N particles each with mass M
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
State gay lussacs law
P=kT
At a constant volume , pressure and absolute temp are directly proportional to the
State Charles’s law
V equals constant times temperature therefore the volume of a gas is directly proportional to the absolute temperature of a substance at constant pressure
What is an ideal gas
A gas in which the ideal gas laws apply therefore there is no other interactions other than perfectly elastic collisions between the gas molecules
What is molar mass?
The mass of one molecule and molar mass is equal to the MR
If the equation for Boltzman constant
K=R/Na
What is the capital N in the pressure
Number of molecules
What is the n in pressure?
The number of moles
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
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
Why is there no potential energy in an ideal gas?
As molecules exert no force on each other except during collisions therefore internal energy equals to the kinetic energy of the particles
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?
No Isaiah at the same temperature, therefore they were both have the same kinetic energy
Defined the internal energy of an ideal gas
The sum of the mean kinetic energies of the particles and there is zero potential energy in the ideal gas
State in words, Boyles law
For a fixed mass of gas at a constant temperature pressure is inversely proportional to volume
Explain Boyles law in terms of the kinetic theory of gases
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.
Explain how newtons law are used in the derivation of the equation PV=1/3Nmc^2
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
State 6 assumptions of an ideal gas
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
State the general characteristics of the Maxwell Boltzman distribution curve
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
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
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.
Use kinetic theory of gases to explain why the pressure of an ideal gas increases when heatead at constant volume
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
Explain why the volume occupied by an ideal gas increases when it is heated at a constant pressure
More collisions per second, this increases pressure
To keep the same a greater volume is required as there are fewer collisions per second
4 assumptions about an ideal gas properties and behaviour when deriving an expression for the pressure of an ideal gas
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
The smoke particles in the Brownian motion are observed to move why
They are colliding with the air molecules
Explain why some of the rms speeds of the particles are less than the average mean speed
There is a range of speeds
Some molecules will have lower speeds than the mean
Stay and explain a situation in which the very high value for specific heat capacity for water is useful
Car cooling systems because it absorbs large amount of heat for small rising temp
internal energy changes when a mass of water at 100°C becomes an equal mass of vapour at 100°C? Explain why
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
The molar mass of hydrogen is 2.02x10^-3 calculate the mass of a hydrogen molecule
Mol=mass/mr
Therefore N/NA=mass/mr
N=1
Therefor mass= 2.02x10^-3/NA
Why do we use kelvin in the equations for ideal gasses
As vol or pressure tends to zero temp also tends to zero, this value of zero is on the Kelvin scale
Brownian motion provides evidence for the kinetic model of gasses, state three assumptions made in the kinetic theory of gases
Forces between particles are negligible except in collisions
Collisions are perfectly elastic
Particle occupy negligible volume compared to the volume of the gas
How can you find mass when the mr of a substance is given
Mass= mr/Na
Explain why there is still some helium on our planet when it should have escaped in the early atmosphere
Helium is an alpha particle which emitted in radioactive decay therfore it is generated
If a particle collides with a container 100 times and has a change of momentum of p what is the average force exerted
100p
