IDEAL GASES Flashcards
1
Q
- What is the atmosphere composed of?
A
- Nitrogen (N2)
- Oxygen (O2)
- Water Vapour
(this depends on the local humidity levels)
2
Q
- What are three properties of gases?
A
- they are miscible
(they mix together) - they form homogenous mixtures
- they are compressible
3
Q
- Why do water and oil not mix together when they are in a liquid state?
A
- oil is less dense than water
- it will rise above the water
- water is more dense than oil
- it will sink below the oil
- they have different intermolecular forces between
their particles
4
Q
- In which state do oil and water mix together?
A
- in a gaseous state
5
Q
- What results in the properties of gases?
A
- the large distances between the gas particles
- this limits the interactions that are possible between
the particles
6
Q
- What is air composed of?
A
- 0.1% volume of gas particles
- 99.9% empty space
7
Q
- How is gas pressure calculated mathematically?
A
- it is the force divided by the given area
- the units of force are Newtons
- the units of area are m²
- the units of pressure is Pascals (Pa)
8
Q
- How else can Newtons be written?
A
- kg m / s²
9
Q
- How else can Pascals (Pa) be written?
A
- N/m²
- kg / (ms²)
- pascals are an extremely small unit
10
Q
- How would we work out the Gas pressure in this diagram?
- the column of the Earth’s atmosphere has a
dimension of 1m x 1m - this is estimated to have a mass of 10 300kg
- the column of gases is pressing down on the surface
of the Earth at sea level - this creates the atmospheric pressure
- the area of the column is 1.00m²
A
- P = m x g / A
- the gravitational force is calculated as F = m x g
- g = Earth’s gravitational constant
- g = 9.8m.s⎺²
∴P = 10 300 kg x 9.81m.s⎺² / 1.00m²
NB:
- if we go to a high mountain
- the height of the column is smaller
- this gives a reduced mass
- it also gives a reduced atmospheric pressure
11
Q
- Why is Mercury harmful to your health?
A
- it is neurotoxic
- it destroys the neurons in oyur brain
12
Q
- What is a Barometer?
A
- it is a weight measuring device
- it measures the weight of the atmospheric gases acting
on the Earth - it is a crude instrument
- it is used for measuring atmospheric pressures
13
Q
- How do we set up a Mercury Barometer?
A
- we fill up a bowl with liquid mercury
- we fill a glass test tube completely with mercury
- we place the glass test tube with the opening facing
downwards - the test tube is placed inside the bowl with Mercury
14
Q
- How does a Mercury Barometer work?
A
- gravity pulls down on the Mercury in the test-tube
- the mercury moves down the test tube
- this creates a vacuum at the top
- the atmospheric pressure is also pushing down on the
liquid mercury in the bowl - this pushes the liquid up into the test tube
15
Q
- How do we express atmospheric pressure using a Mercury Barometer?
A
- when a balance is reached between the forces in the
Mercury barometer - the height of Mercury in the test tube is measured
- in this case it is 760mm
- this is the atmospheric pressure
16
Q
- What is are other equivalent units of 1 atm?
A
- 760 mmHg
- 760 torr
- 101.325 kPa
17
Q
- What is a torr?
A
- it is a unit of measurement
- it is equal to 1 mmHg
18
Q
- What is one bar equal to?
A
- 100 kPa
- 0.986923 atm
19
Q
- How do we calculate the pressure of an enclosed gas?
A
- using an open ended manometer
20
Q
- What does an open-end manometer consist of?
A
- it has a glass bulb on the left side
- this is filled with an unknown gas
- it has a U shaped tube
- the U shaped tube is filled with Mercury
- the right side of the U-tube is open to the
atmosphere
21
Q
- How does an Open end Manometer work?
A
- the atmosphere is pushing down on the right side of
the U-tube - this is pushing the Mercury down
- the gas is pushing down on the mercury on the left
side of the U-tube
22
Q
- What happens when the gas pressure is equal to the atmospheric pressure in the Open End Manometer?
A
- the levels of the mercury in the two arms of the U-tube
will be the same
23
Q
- What happens when the gas pressure is less than the atmospheric pressure in the Open End Manometer?
A
- the right side of the U-tube will be lower than the left-
side
24
Q
- What happens when the gas pressure is more than the atmospheric pressure in the Open End Manometer?
A
- the left side of the U-tube will be lower than the right-
side
25
Q
- What determines the pressure that an enclosed gas exerts?
A
- the frequency of the collisions with the inner container
walls - the intensity of these collisions
26
Q
- What kind of motion do the gas particles inside the box have?
A
- constant motion
- this type of motion is random
- it is called Brownian motion
27
Q
- What does the Brownian motion of these particles result in?
A
- the randomness of the motion results in continuous
collisions between the gas particles - this leads to a redirection of these particles in different
directions
28
Q
- What creates pressure in this container?
A
- the gas particles collide frequently with the inner
walls of the container - this creates pressure
29
Q
- Which two factors determine the magnitude of the pressure inside the box?
A
- THE FREQUENCY OF THE COLLISIONS
- these happen with the inner walls of the box
- THE INTENSITY OF THE COLLISIONS
30
Q
- What happens when the frequency of the collisions of the particles is higher?
A
- the higher the pressure within the box will be
31
Q
- What happens when the intensity of the collisions of the particles is higher?
A
- the higher the force of the collision
- the pressure is higher
32
Q
- What keeps a balloon from capsizing on itself?
A
- the collisions of the particles within the balloon
- these collisions are caused by the Brownian motion of
the particles
33
Q
- What will happen to the pressure inside a container of gas if the temperature of the gas is increased?
A
A HIGHER TEMPERATURE RESULTS IN:
- the particles moving faster
- the particles have more kinetic energy
- they collide with the walls of the container more
frequently
- they collide with the walls with more force
- the total pressure inside the container increases
34
Q
- What will happen to the pressure inside a container of gas if the container is reduced to half its volume?
A
A HALVED CONTAINER RESULTS IN:
- the particles are moving at the same speed
- they will collide with the walls of the container with
the same force
- they will travel a much shorter distance before they
collide with the walls of the container
- they will collide more frequently
- the pressure will increase
