Chemistry 11 Unit 5 Gases and Atmospheric Chemistry Flashcards Preview

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Flashcards in Chemistry 11 Unit 5 Gases and Atmospheric Chemistry Deck (26):
1

Melting point temperature and Freezing point temperature

MP: The temperature at which a solid changes to a liquid

FP: The temperature at which a liquid changes to a solid

*MP and FP temperatures are ALWAYS EQUAL

2

Normal Melting Point Temperature vs. Normal Freezing Point Temperature

Normal MP: temperature at which a solid changes to a liquid at One Atmosphere of Pressure

Normal FP: the temperature at which a liquid changes to a solid at One Atmosphere of Pressure

*pressure impacts the point temperatures (above and below sea level)

3

Boiling Point Temperature vs. Normal Boiling Point Temperature

BP temperature: Temperature at which a liquid changes to a gas

Normal BP temperature: the temperature at which a liquid changes to a gas at One Atmosphere of Pressure

*BP increases with pressure

**BP = temperature where the vapour pressure = atmospheric pressure

4

Heating and Cooling Curves

Axis:
Y: Temperature (degree Celsius)
X: Time

Heating Curve:
Low to High
First point /: Solid
First Straight line: Melting (MP)
Second Point /: Liquid
Second Straight line: vaporizing (boiling/BP)
Third point /: Gas
^Endothermic (need heat, temperature is going up)

Cooling Curve:
High to low
First Point /: Gas
First straight line: Condensing
Second Point /: Liquid
Second straight line: Freezing (solidifying)
Third Point /: Solid
^Exothermic (feel hot)

5

The Kinetic Molecular Theory (KMT)

A theory about how atoms and molecules (esp. GASES) behave and how it related to the ways we have to look at the things around us

Describes a gas as:
-large number of small particles (atoms or molecules)
-constant, random motion.
-The rapidly moving particles constantly collide with each other and with the walls of the container.
-gases travel in a straight line, do not lose energy when they bounce off a wall
-The kinetic energy of a gas is a measure of its Kelvin temperature. Individual gas molecules have different speeds, but the temperature and kinetic energy of the gas refer to the average of these speeds.
-The average kinetic energy of a gas particle is directly proportional to the temperature.  An increase in temperature increases the speed in which the gas molecules move.
-All gases at a given temperature have the same average kinetic energy.
-Lighter gas molecules move faster than heavier molecules.


5 main points:
1. all matter is made of atoms (smallest unit of each element)

2. atoms have an energy of motion that we feel as temperature-translational, vibrational or rotational
-At any given time, molecules are moving in many different directions at many different speeds.

3. Temperature we can extrapolate ->Absolute zero: motion of the atoms and molecules would stop

4. Pressure of a gas is due to the motion of the atoms or molecules of gas striking the object bear that pressure
-collisions are elastic (no friction and do not lose energy when colliding)

5. very large distance between the particles of a gas compared to the size of the particles (size of the particle can be considered negligible)

6

STP?

physical properties of a substance (including vapour pressure, boiling point, freezing point etc.) are determined at Standard temperature and Pressure

O degrees Celcius and 1 atmosphere of pressure

7

Diffusion

spreading of one substance through another due to random motion of particles

Rate of diffusion increases with increasing temperature and is greater in substances with lower molar masses (smaller diffuses faster)

-therefore if question asks which substance will diffuse quicker, pick one that has lower molar mass

8

Vapour pressure
-gas

The pressure created by gas molecules when a liquid changes to a gas (vaporizes) in a closed system

When?
Vaporizes when it has enough ENERGY to overcome the IMF's holding the molecules within the liquid (able to break apart to become gas)

Strong IMF: low vapour pressure (tightly packed, harder to convert to gas state easily) i.e. water
Weak IMF: high vapour pressure (i.e. nail polish remover)

Low Temperature = low vapour pressure
High Temperature = high vapour pressure
*temperature is the ONLY FACTOR that will affect the vapour pressure of a substance

***
High vapour pressure = weak IMF -->smallest non-polar molecule

9

Vapour pressure and Boiling point relationship

When does Boiling occur?

When does Boiling occur:
When the pressure pushing the particles apart (vapour pressure) is GREATER OR EQUAL to the pressure holding the particles together (atmospheric pressure)

Pvap = Patm or Pvap > Patm

*
(boiling occurs when the forces to break apart of stronger than the forces keeping them together)

10

Pressure conversion

1 atm (atmosphere) = 101.325 kPa = 760 mmHg = 760 Torr = 14.7 Psi

*given in data booklet

11

Temperature (Kelvins) conversion with Degree Celcius

0 degrees Celcius = 273 K

12

Gas Laws

Boyle, Charles, Guy-Lussac, Avogadro

Boyle's Law: P1V1 = P2V2
Temperature is constant (pressure and volume are inversely related)
Ex: marshmallow in syringe (increase volume, decrease pressure)-->lungs

Charle's Law: V1/T1 = V2/T2
Pressure is constant (volume and temperature directly proportional)
Ex: Bottle in fridge, hot air balloon (increase in temperature, increase in volume)

Guy-Lussac's Law: P1/T1 = P2/T2
Volume is constant (pressure and temperature directly proportional)
Ex: Hot Can in cold water (decrease in temperature, decrease in pressure)

Avogadro's Law: "equal volumes of different gases at the same temperature and pressure have the same number of molecules (or atoms if the gas is monatomic)"
Ex: Balloon increases in size with increase in particles
-equal volume, same T and P = same #p

Temperature in K
Pressure doesn't matter as long as consistent
Volume doesn't matter as long as consistent

13

Ideal gas laws and characteristics

PV = nRT

*T is K
*V is L
R is a constant depending on P

Characteristics of Idea Gases:
-gas particles have zero volume
-no attractive forces between the particles
-the kinetic energy of the particles is proportional to absolute temperature (meaning that molecular motion ceases if reach absolute 0, gases at same temperature will have same average kinetic energy)

*not all gases will follow the rules (if so, then would never condense into a liquid)

REAL GASES act most like an ideal gas at HIGH TEMPERATURES (move faster, no attractive forces) and LOW PRESSURES (not close together)

-stay in same condition, just converting to solve for variables
*n = V/MV is only at STP

14

Combined Gas Law

P1V1/T1 = P2V2/T2

-n and R both constant
-take a gas and move to different condition

Temperature must be in K, but P and V can be any unit as long as same units used

-can eliminate variables if they are constants (just becomes the gas laws like Charles, Boyle and GL)

*write out given information

15

Gas Stoichiometry

-similar to mole stoichiometry

Use PV = nRT
-still needs mole for mole ratio

Ex: ideal gas law for moles, then ideal gas law for other (v, p,t etc.)

Ideal gas law for moles, then n=m/mm for mass

n=m/mm for moles, then idea gas law for V,t, p etc.

16

Endothermic vs. exothermic

Endo: requires heat Ex: S to L, L to G

Exo: releases heat Ex: L to S

17

Phase Transitions

S to L = melting (not necessarily hot) Endothermic (needs heat)

L to S = freezing/solidification (not necessarily cold) Exothermic



L to G: boiling/vaporization Endothermic
*Evaporate is below BP (i.e. sweat)
Vaporate is above BP

G to L: Condensing Exothermic

S to G: sublimation (ex: Dry ice) Endothermic

G to S: Deposition (solid deposits) Exothermic
ex: Frost on car windshield

18

Dalton's Law of Partial pressure

The total pressure of a gaseous mixture is equal to the sum of the pressures of the individual gases (known as partial pressures)

Ptot = PA + PB + PC...

Find partial pressure of a gas: PA = Ptot * (N of A/total N)

Total N is sum of all moles
Total V is sum of all Volumes

*use total pressure equation to check is partial pressures are correct

Also use law to find pressure of gas in a mixture containing water:
Pdrygas = Ptotal - Ph20 (water vapour)

^as long as pressure same okay
Check Table of Vapour Pressure of Water for pressure of water at different temperatures

19

Theorizing pressure, temperature and volume

when changing states from solid to liquid to gas...

energy/heat is needed to spread the particles a part (endothermic). When this happens, the area around the substance becomes cold.

When changing states from gas to liquid to solid...

energy/heat release energy to compress and reduce the space between the molecules. As molecules become more compact, energy becomes vibrational (not moving-almost no energy)


The more frequently these molecules collide with the walls of the container, the greater the net force and hence the greater the pressure they exert on the walls of the container (ex: decrease volume, increase in pressure because less space causes more collisions)

20

Pressure relating with in above sea level, sea level, below sea level

Above sea level (ex. mountains) have low pressure. Therefore, Pvap is greater or equal to Patm, allowing boiling to occur faster (at a lower temperature)

Below sea level (ex: underwater) have high pressure. Therefore it takes longer for water to boil (at a higher temperature)

Boiling is simply changing from liquid to gas

21

Temperature and kinetic energy

Temperature and kinetic energy are essentially the same idea = how fast particles are moving (ex: High temperature = fast movement)

Substances are solids at lower temperatures and liquids and gases at higher temperatures -->definition of temperature as average kinetic energy: since the molecules in gases and liquids have more freedom of movement, they have a higher average velocity.

22

Temperature and effects

When a solid is heated, its temperature and vapour pressure increase because the molecules of a solid have increasing kinetic energy

During melting: heat is absorbed as the solid is converted into a liquid at a constant temperature

During boiling: heat is absorbed as liquid is converted into a gas at a constant temperature

In gas phase, the temperature increases as gases require additional kinetic energy

23

Closed container/system means?

Volume remains constant

24

Three states of matter and comparisons

Solid:
-high density
-non-compressible (almost, some if use special machine)
-fixed shape
-fixed volume
-strong IMF
-no diffusion
-low energy
-vibrational motion (basically not moving)
-can feel
-particles are close together

Liquid
-medium density
-non-compressible (almost, some if use special machine)
-variable shape
-fixed volume
-Moderate IMF
-diffusion occurs (i.e. water and food colouring)
-Medium energy
-vibrational, rotational, translational motion
-can feel
-particles are moderately close together

Gas
-low density
-compressible
-variable shape
-variable volume
-Weak IMF
-diffusion occurs (i.e. perfume)
-high energy
-vibrational, rotational, translational motion
-cannot feel
-particles are far a part

25

Evaporation vs. vaporization

Evaporation: change from liquid to gas below boiling point

Vaporization: change from liquid to gas above boiling point

both are forms of boiling (L to G)

26

Density units

d = m/v

g/L