properties and behaviours of gases

Question 1

Gases and volume

Answer 1

Unlike solids and liquids which have definite volume, gases expand to fill any space available to them. Their volume is defined by the volume of the container they are in. Gases also take up more volumes in the same substances of liquid or solid form (ex 100 ml of water fills 200 L of space in gas form)

Question 2

Gas properties

Answer 2

• shape and volume depend on container
• compressible and less organized
• . volume decreases when pressure is exerted but with solids and liquids, the particles cannot move closer together
• gases expand when heated but pressure remains constant (solids and liquids too but to much smaller degree).
• low viscosity and less dense.
• they are also always miscible

Question 3

Liquid properties

Answer 3

Variable shape but constant volume, incompressible but particles are able to slide over each other

Question 4

Solid properties

Answer 4

Constant shape and volume, incompressible and particles are fully organized

Question 5

Factors that determine state

Answer 5

Forces between particles: ions, atoms or molecules

And kinetic energy: which has the tendency to pull them apart

Question 6

No forces?

Answer 6

All substances would be gases so forces are necessary for solids and liquids

Question 7

Stronger forces

Answer 7

Greater the amount of energy to pull them apart. more strong forces= more solid compound (where ionic compounds are most definitely solid. weaker forces (like polar molecules) could be in any state of matter.

Question 8

How are polar molecules attracted?

Answer 8

Partial charges or dipoles which allow them to create dipole-dipole forces of attraction. Hydrogen bonded to a F,O or N make a hydrogen bond which is a very strong type of polar attraction.

Question 9

Non polar molecule attraction

Answer 9

Temporary dipoles which creates London forces. very weak. large molecules like C30H62 are solids which mid size C5H12 would be liquid. small ones like CO2 would be gases

Question 10

Kinetic energy of particles

Answer 10

Remember vibrational, rotational, translational?

Question 11

Temperature and kinetic energy

Answer 11

If there was 0 kin energy, everything would be a solid (not possible). by adding kin energy (heat), you increate types of movement in substance. if enough is added, the particles will overcome attractive forces and become gases.

Question 12

“the potential energy of the substance is increased.”

Answer 12

The energy given to overcome the attractive forces between the particles is stored in particles.

Question 13

Kinetic molecular theory

Answer 13

• particles area always moving and collisions are completely elastic. individual gas particles have a negligible volume and that attractive forces between particles of gas are also negligible.
• inform the news of boyle and charles’s from this

Question 14

Ideal gases

Answer 14

• point mass
• no attractive or repulsive force
• move in perfectly straight lines
• collisions are completely elastic
• has high translational kinetic energy
• average kinetic energy is directly related to temperature
  as pressure increases and/or temperature decreases, gases deviate further from ideal behaviour

Question 15

Closed system

Answer 15

the total amount of matter remains constant and matter can neither enter nor leave.

Question 16

Open system

Answer 16

Everything moves freely

Question 17

Isolated system

Answer 17

Neither matter or energy can move in or out

Question 18

pressure

Answer 18

Force exerted per unit of surface area (N/m2)

Question 19

Atmospheric pressure

Answer 19

• all gases are pulsed by gravity to earth and exert pressure on all objects on earth. atmospheric pressure is the force of a column of air on Earth’s surface divided by the area at the base of the column. it gets lower and the density of air is decreased as you move higher in altitude since as you move up, there are less air particles above you, pushing down

Question 20

Measuring pressure

Answer 20

• absolute pressure, actual pressure exerted by a gas using a barometer. pressure on the liquid will change depending on the weather and the altitude
• relative pressure (pressure exerted by a gas relative to the atmospheric pressure which is measured using a manometer.

Question 21

Stormy weather and headaches

Answer 21

• people have headaches on rainy days since there is less pressure due to storm and they are used to pushing against a certain atmospheric pressure. since the pressure is lower, the head swells to try to push back causing pain
• pressure is lower in storm since air gets sucked up into clouds
• higher altitude has lower pressure

Question 22

Standard ambient temperature and pressure

Answer 22

Standard conditions that help compare gases

Question 23

Boyle’s law

Answer 23

The volume of a given mas of a gas at constant temperature is inversely proportional to its pressure.
- Boyle’s Law can be rearranged to compare the change in initial and final volume and pressure of a gas sample

p1v1=p2v2

Question 24

Using Kinetic Molecular Theory to Explain Boyle’s Law

Answer 24

• The pressure on the walls of a container filled with gas is caused by collisions between the gas molecules and the container’s walls
• Each collision exerts a force on the wall.
• When the volume of the container is increased, the pressure is decreased because there is more space for the gas particles to move around. However, when the volume of the container is decreased, there is less space for particles to move around, which leads to more collisions and thus, more pressure

Question 25

Celsius to kelvin

Answer 25

Add 273

Question 26

Charles’ law

Answer 26

The volume of a fixed amount of any gas at fixed pressure is directly proportional to its Kelvin temperature.

“Carlie brown was a T over V show”

V/T 1=V/T2

Question 27

Charles’ law proof

Answer 27

When a fixed quantity of a gas in a cylinder with a moveable 
piston is heated, the kinetic energy of the gas particles is 
increased causing the piston to move up. the pressure is kept constant.

Question 28

Gay-lussac’s law

Answer 28

At constant volume, the pressure of a fixed mass of a gas is directly proportional to its Kelvin temperature

“felt societal pressure to change his name… different”

P1/T1=P2/T2

Question 29

combined gas law

Answer 29

amount of gas in moles remains constant.

any units may be used as long as they match but temperature must always be in kelvin

P1V1/T1=P2V2=T2

Question 30

law of combining volumes

Answer 30

when gases react, the volumes of the gaseous reactants and products, measured under the same conditions of temperature and pressure are always in whole number mole ratios.

Question 31

avogadro’s law

Answer 31

all equal volumes of all equal ideal gases at the same temperature and pressure contain the same number of molecules, regardless of mass. - this is because there is so much space between the molecules (and gases are just unique).

this means that you can find the moles and the volumes from the balanced eon

Question 32

1 mol of an ideal gas

Answer 32

in litres at STP occupies a constant volume of 22.4 L thus you can determine the number of moles

Question 33

determining molar volume of an ideal gas

Answer 33

• based on what we just learned about avogadro’s law, one mole of a gas occupies the same volume as one mole of any other gas at the same temperature and pressure. thus, it is possible to calculate molar volume

Question 34

molar volume

Answer 34

space that is occupied by one mole of gas. L/Mol

Question 35

ideal gas law

Answer 35

volume must be in L, temperature must be in K, pressure must be in Kpa

applies to any gas for which the ideal laws are valid

Question 36

universal gas constant

Answer 36

8.314 L/Mol -Kelvin

Question 37

density

Answer 37

measured in g/l which is mad of gas per litre. the relationship between molar mass and the density of a gas ca be combined with the ideal gas law as follows

Question 38

dalton’s law of partial pressures

Answer 38

total pressure of a mixture of gases is the sum of the pressures of each of the individual gases

Question 39

collecting gas in a lab

Answer 39

downward displacement of water. this works best with gases that have a low solubility in water (see textbook)

Question 40

important Dalton’s law notes

Answer 40

water vapour molecules will mix with the gas molecules you are trying to collect. According to Dalton’s law of partial pressure, you will need to take this into account when measuring the total volume of gas produced.

• thus, to determine the pressure of the collected gas, often referred to as “dry gas”, without the water vapour, you must subtract the pressure of them after vapour from the total pressure
• this can be done using a table of established values for the partial pressure of water at various temperatures

Question 41

Ideal gases vs real gases

Answer 41

• at STP most behave ideally but at high/low temperature, they don’t
• particles of gas have volume and molecules do attract each other, collisions are not elastic and they don’t move in straight lines
• gases at high/low pressures have smaller volumes making the molecules closer together which increase interaction. that also means that the total volume is smaller and that empty space between particles has decreased.

Question 42

relationship between atmospheric pressure and altitude

Answer 42

each layer of the atmosphere exerts a force on the layer below it. Because the weight of the entire column of air exerts a force on the bottom layer, the bottom layer is the most compressed. As the altitude increases, the amount of air above that level becomes smaller and exerts a smaller force on the air just below it, the higher layers of air are less compressed than the lower layers.

Question 43

Graham’s law

Answer 43

• gas molecules are constantly moving.

- the higher the molar mass, the slower it can effuse through a barrier

Question 44

Note on Kinetic Molecular Theory

Answer 44

• it provides a scientific model for explaining the behaviour of gases. the way it does that is by assuming an “ideal gas”

Question 45

gases can be easily compressed because

Answer 45

they have negligible intermolecular forces

Question 46

when do real gases deviate most from ideal behaviour

Answer 46

A real gas can be considered to behave like an ideal gas under low pressure and high temperature. As the temperature is decreased or the pressure increased, the behavior of the gas deviates from that of an ideal gas.