Chapter 5: States of Matter

Question 1

States of matter are characterized by

Answer 1

Different energies of particles

Question 2

Kinetic theory of matter:

Answer 2

Energy of particles is directly proportional to the temperature in the Kelvin scale of the system.

State of matter at given temp and pressure is determined by strength of intermolecular force between particles

Question 3

Properties of particles in solid, liquid, gas states

Answer 3

S: closely packed, inter particle force strong, vibrate in position, fixed shape and volume
L: more spread, force weaker, slide over each other, no fixed shape, fixed volume
G: spread out, force negligible, move freely, no fixed shape and volume

Question 4

Explain the heating curve:

Answer 4

Solid is heated, vibrational E increases and so does temp. Line going up

Melting point. Vibrations enough energetic for molecules to move away from fixed positions to form liquid. E added at this stage used to break intermolecular force, not raise KE, so temp (line) constant

Liquid heated, KE gained, temp goes up

Boiling point. Enough energy to break all intermolecular forces and form gas. Needs more E than melting as all forces must break. KE and hence temp contstant. Gas bubbles visible throughout liquid

Gas heated under pressure, KE and temp increase

Question 5

Basic assumptions of kinetic theory as applied to a ideal gas:

Answer 5

Ideal gas strictly obeys these:

1. Molecules are in continuous random motion
2. Volume occupied by molecules negligible compared to total volume occupied by gas. Ie molecules are point masses
3. Intermolecular force of attraction is negligible
4. Colliding molecules, perfectly elastic, no loss/gain of E
5. Pressie of gas is due to collision of molecules against containers walls

Question 6

Temp in Kevin is known as

Answer 6

Absolute temp

Question 7

Absolute zero, 0K, is…

Answer 7

Point of zero kinetic energy of particles

Question 8

0K=

Answer 8

-273°C

Question 9

Celsius –> Kelvin ?

Answer 9

Add 273

Question 10

How many Pa in 1 bar

Answer 10

10^5 ie 1 atm

Question 11

Cm3 –> dm3 ??

Answer 11

Divide by 1000

Question 12

1000cm3=xdm3

Answer 12

1dm3

Question 13

Dm3 –> m3 ??

Answer 13

Divide by 1000

Question 14

1m3=xdm3

Answer 14

1000dm3

Question 15

Boyle’s law:

Answer 15

Volume occupied by fixed mass of gas varies inversely with it’s pressure at constant temp

Question 16

Volume of gas=

Answer 16

Containers volume

Question 17

Pressure increases as

Answer 17

Frequency or energy of collisions increases

Question 18

Boyle’s law relationship

Answer 18

P α 1/V

PV is a constant

Question 19

Graphs of Boyle’s law

Answer 19

V X axis, p y axis. Decreasing curve

1/V X axis, P y axis. Straight line through origin

P X axis, pv y axis. Constant (—)

Question 20

Charles law:

Answer 20

Volume of given mass of gas directly proportional to it’s absolute temp, at constant pressure.

Question 21

Charles law relationship

Answer 21

VαT

V/T= a constant

Question 22

Charles law graph

Answer 22

Temp/K X axis, V y axis. Straight line through origin which is absolute 0 (0K)

Question 23

Relationship between temp and pressure

Answer 23

Increase in temp increase average KE of particles and they move faster and collide walls with more energy and frequency, raising pressure.

If volume is held constant pressure directly proportional to absolute temp
PαT
P/T= a constant

Question 24

Graph of PαT

Answer 24

Temp/K X axis, P y axis. Straight line through 0K at origin

Question 25

Charles laws:

Answer 25

VαT at const P PαT at const V

Question 26

Combined gas law equation

Answer 26

PV/T= a constant OR P1V1/T1=P2V2/T2 (1-ini, 2-fin)

Question 27

Ideal gas equation:

Answer 27

PV=nRT Derived from 3 gas laws for fixed mass of gas Practice the derivation

Question 28

Avogadros law:

Answer 28

V α n | At const temp, and pressure, equal volumes of gases contain equal no of moles

Question 29

What is R?

Answer 29

Universal gas constant

Question 30

``` When using ideal gas equation, P must be in: 1. V: 2. No of moles: 3. Temp: 4. ```

Answer 30

1. Pa 2. m3 3. m/M 4: K

Question 31

How do real gases behave

Answer 31

Deviated to some extent from ideal behavior

Question 32

Ideal gas defined as

Answer 32

Obeys ideal gas law PV=nRT under all conditions. One mole of gas relationship PV/RT=1. So graph of PV/RT against P for 1 mole is a horizontal line of intercept 1

Question 33

Real gas almost behaves like an ideal gas at

Answer 33

Low pressure | High temp

Question 34

Real gas shows greatest deviation at

Answer 34

High pressure | Low temp

Question 35

How to interpret when real gases behave most and least like ideal gases

Answer 35

Question validity of 2 assumptions from kinetic molecular theory 1) volume of gas particles negligible 2) no attractive forces between particles

Question 36

Explain why real gases can behave as ideal gases at low pressure, and not high in terms of volume

Answer 36

At low, volume of particles is about 0.05% of total so it's valid to call it negligible At high, space between then is reduced so percentage volume of particles increases to 20% of total - not negligible. As a result, volume of real gas at high pres is larger than predicted from ideal gas law

Question 37

Explain why real gases can behave as ideal gases at low pressure, and not high in terms of force of attraction

Answer 37

At low pressure, particles are wide spread so forces between are negligible. But high pressure, particles are closer so attractive forces strengthen. Reduce effect of pressure of gas. Low temp increase deviation because lower KE increases strength of forces.

Question 38

Which conditions being invalid make a real gas deviate from an ideal gas

Answer 38

High pressure and low temp molecules are close and volume occupied by individual molecules can't be ignored compared to total. And intermolecular force of attraction is large and can't be ignored

Question 39

Particles in liquid :

Answer 39

- have more KE than those in solid state - not in fixed positions - in constant motion, bouncing or colliding off eachother - closely packed but less than solid - attrsctive forces less than in solid

Question 40

Melting:

Answer 40

Solid changes its state when heated. Change happens because particles gain KE and vibrate with greater amplitude.

Question 41

Melting point:

Answer 41

Temp at which energy supplied is sufficient to over come binding force

Question 42

Vaporization :

Answer 42

Liquid surface is flat, expect near walls of container. this is because particles at surface are attracted inwards and sideways by other particles. Fastest moving surface particles escape into gas state.

Question 43

Why does temp decrease with evaporation

Answer 43

Escape of fastest particles decreases average KE of liquid so temp of liquid decreases with evaporation.

Question 44

What increases rate of evaporation

Answer 44

Higher the temp the faster rate of evaporation.

Question 45

Evaporation takes place at what temp

Answer 45

All the time | Because particles escape from surface all the time

Question 46

Evaporation in closed container

Answer 46

Escaped particles collect in space above surface and collide with eachother and walls

Question 47

Vapor pressure is

Answer 47

Vapor formed by escaping particles from particles in closed container exert a pressure

Question 48

Vapor pressure depends on:

Answer 48

Temp of liquid | Characteristics of liquid as force holding particles is different for each

Question 49

Saturated vapor pressure

Answer 49

As more and more particles escape molecules in vapor become close together and some condense back by hitting liquid surface. When 2 opposing changes are at same time an equilibrium is reached (with molecules going from liquid to vapor as same rate as vapor to liquid) between no of particles leaving and reentering liquid when vapor pressure remains constant at given temp. Pressure exerted by vapor at equilibrium is sat vap pres

Question 50

Boiling

Answer 50

Liquid in contact with air is heated, it's vapor pressure increases until a temp is reached at which vapor pressure = atmospheric pressure.

Question 51

Liquid boils when ... Bp relationship with vapor pressure

Answer 51

Saturated vapor pressure = atmospheric pressure Bp increases as vapor pressure does

Question 52

Saturated vapor pressure is a characteristic of liquid. Meaning?

Answer 52

Constant for given liquid at given temperature (+temp, +KE, able to overcome)

Question 53

Why does vapor condense back

Answer 53

Molecules in vapor come close as more molecules escape. Eventually molecules with lower KE are not able to over come attractive force of neighbouring molecules

Question 54

At equilibrium concentration of water molecules in vapor is

Answer 54

Constant