15 Gas Laws Flashcards
How is P1 and T1 related to P2 and T2?
P1 is pressure before
T1 is temperature before
P2 is pressure after
T2 is temperature after
Explain why a hot balloon expands
As temperature rises, the particles gain kinetic energy
Particles move faster
More collisions per unit time AND particles collide with more force
Pressure = force / area
Increased pressure on the inside of the balloon, with same pressure on the outside results in greater forces on inside compared to outside of balloon - balloon skin stretches outward
What are the control variables for the Boyles’ Law investigation where the volume of a gas was measured as the pressure was varied?
Moles/amount of gas
Temperature of gas
Use the equation below to calculate the new volume of a gas as its pressure increased from 100kPa to 200kPa.
Its initial volume was 50cm3.
P2V2 = P1 V1
V2 = P1V1/P2
V2 = 100kPa x 50cm3 / 200kPa
V2 = 25cm3
Convert 373K to ºC
ºC = 373 - 273
= 100ºC
Convert 100K to ºC
ºC = 100 - 273
= -173ºC
Name the independent and dependent variable for the Pressure-Temperature experiment
Independent : temperature gas
Dependent : pressure of gas
What happens to the pressure of a gas if the volume is halved?
Explain why this happens.
As volume is halved, pressure is doubled
There are double the number of particles per unit volume
Double the number of collision per unit time on the sides of the container
Double the force means double the pressure
P = F/A
Name the independent and dependent variable for Boyle’s law experiment
Independent : pressure
Dependent : volume of gas
What happens to the movement of the particles of a gas when they are heated?
The particles gain energy
KE of particles increases
Particles move faster
Convert 100ºC to Kelvin
K = 100 + 273
= 373 K
How would you represent the motion of a smoke particles in air? (Brownian motion)
Uses arrows of different length and directions to show continual random movement.
What is the unit for volume of a gas?
cm3 or m3
How many Pa are in a kPa?
1000 Pa = 1 kPa
From the graph, how is pressure of a gas related to its volume? (at constant temperature and moles of gas)
Pressure is inversely proportional to volume at constant temperature and moles of gas
Convert -273ºC to Kelvin
K = -273 + 273
= 0 K
A pupils stated that as the temperature of a gas in degrees celsius is doubles, the kinetic energy of the gas must also double.
Is this statement true or false?
False
At temperature of a gas in kelvin doubled, the average kinetic energy of the particles doubles
Temperature must be in kelvins!!
How is P1 and V1 related to P2 and V2?
P1 is pressure before
V1 is volume before
P2 is pressure after
V2 is volume is after
Use the pressure-temperature equation to work out the new temperature for a gas where the pressure was decreased from 100kPa to 50kPa
Intial temperature was 40K.
T2/P2 = T1/P1
(write the equation with T2 first- this makes it easier to rearrange!!)
T2= T1P2/P1
T2= 40K x 50kPa / 100kPa
T2 = 20K
How can Brownian motion be observed?
Random jerky movement of smoke particles in a smoke cell through a microscope
A pupils stated that as the temperature of a gas in kelvin is doubled, the average speed of the gas must also double.
Is this statement true or false?
False
As temperature of a gas in kelvin doubles, the average kinetic energy of the particles doubles, NOT the average speed
Why does an air balloon grow bigger when air is heated
As temperature of a gas increases, kinetic energy increases
particles move with greater speed and hit the sides of the balloon more frequently AND with more force
Pressure = force / area
Greater force on walls of balloon increases the pressure of the gas pushing the walls of the balloon outward.
From the graph, how is pressure related to temperature in kelvin of a gas - at the same volume and mole of gas?
Pressure is proportional to temperature in kelvin at the same volume and moles of gas
What is Brownian motion?
It is the continuous and random zig zag movement of microscopic particles in a fluid, as a result of continuous bombardment from molecules of the surrounding medium.
(pollen in water)
Use the equation below to calculate the original pressure of a gas as its volume increased from 50cm3 to 100cm3
Its final pressure was 40kPa.
P<span>1</span>V<span>1</span> = P2 V2
P1 = P2V2/V1
P1 = 40kPa x 100cm3 / 50cm3
P1 = 80kPa
Use the equation below to calculate the new pressure of a gas as its volume decreased from 100cm3 to 50cm3.
Its initial pressure was 1atm.
P2V2 = P1 V1
P2 = P1V1/V2
P2 = 1atm x 100cm3 / 50cm3
P2 = 2atm
How is pressure of a gas related to its volume?
What would a graph of pressure against volume look like?
Pressure is inversely proportional to volume
As pressure doubles, volume halves
(For same moles of gas and temperature)
State Boyle’s Law
Pressure is inversely proportional to volume- at a constant temperature.
If pressure of a gas is doubled, its volume would halve
A pupils stated that as the temperature of a gas in kelvin is doubles, the average speed of the gas must also double.
Is this statement true or false?
False
At t_emperature of a gas in kelvin doubles,_ the average kinetic energy of the particles doubles, NOT the average speed
How is temperture related to the average KE of particles
Temperature is proportional to the average KE of the particles
NOTE: Temperature is not proportional to the average velocity of the particles!!
What are the control variables for the investigation where pressure of a gas was measured as temperature was varied?
Moles/mass of gas
Volume of gas
Use the pressure-temperature equation to work out the initial pressure for a gas where the temperature was increased from 100K to 200K
Final pressure was 5 atm.
P1/T1 = P2/T2
(write the equation with P1 first- this makes it easier to rearrange!!)
P1= P2T1/T2
P1= 5atm x 100K / 200K
P1 = 2.5atm
How does the pressure of a gas relate to it temperature in kelvin?
What would a graph of pressure against temperature look like?
Pressure is proportional to temperature in kelvin
(For same moles of gas and volume)
Straight time through the origin
How is pressure related to temperature in degrees celsius?
Pressure is linearly related to temperature in degrees celsius.
(For same moles of gas and volume)
It is a straight line but does not go through the origin.
Convert 0ºC to Kelvin
K = 0 + 273
= 273 K
Convert 0K to ºC
ºC = 0 - 273
= -273ºC
Use the pressure-temperature equation to work out the initial temperature for a gas where the pressure was decreased from 100Pa to 50Pa
final temperature 15K.
T1/P1 = T2/P2
(write the equation with Ti first- this makes it easier to rearrange!!)
T1= T2P1/P2
T1= 15K x 100Pa /50Pa
T1 = 30K
Use the pressure-temperature equation to work out the new pressure for a gas where the temperature was increased from 100K to 200K
Intial pressure was 3 atm.
P2/T2 = P1/T1
(write the equation with P2 first- this makes it easier to rearrange!!)
P2= P1T2/T1
P2= 3 atm x 200K / 100K
P2 = 6atm
Using data only, how can you show that variables are proportional?
Variables which are proportional give a straight line through the origin.
Therefore the gradient is always the same.
rise/run or the ratio of the data is always the same!
Calculate the ratio of each data set and comment on if they are the same.
Using data only, how can you show that data is inversely proportional?
As one doubles, the other halves, therefore the product is always the same!
The product of each data set is the same
Volume x pressure = constant
- Example calculations:*
- Trial 1 - 2.00 x 6.00 = 12.00*
- Trial 2 - 3.00 x 4.00 = 12.00*
- Trial 3 - 4.00 x 3.00 = 12.00*
