V. Physical Behavior of Matter J Deutsch 2003 2 Matter is classified as a pure substance or as a...

V. Physical Behavior of Matter

J Deutsch 2003 2

Matter is classified as a pure substance or as a mixture of substances. (3.1q)

Substances Mixtures

Elements Diatomic Elements

Compounds

J Deutsch 2003 3

A pure substance (element or compound) has a constant composition and constant properties throughout a given sample, and from sample to sample. (3.1r)

All substances are homogeneous.

J Deutsch 2003 4

Elements are substances that are composed of atoms that have the same atomic number. Elements cannot be broken down by chemical change. (3.1u)

There are more than 100 different elements

Elements are represented by chemical symbols

The first letter of the symbol is always a capital letter the rest are lower case

A temporary symbol

Nitrogen Neon

J Deutsch 2003 5

Some elements are diatomic. They come in pairs when not combined with other elements. Diatomic Elements

– Hydrogen

– Oxygen

– Nitrogen

– Chlorine

– Bromine

– Iodine

– Fluorine

Neon is a monatomic element

Nitrogen is a diatomic element

Br2 I2 N2 Cl2 H2 O2 F2

J Deutsch 2003 6

Compounds are substances that are composed of two or more different elements chemically combined. The elements in a compound are in fixed

proportions A compound can only be decomposed by

chemical means Compounds are represented by chemical

formulas Compounds are electrically

neutral

J Deutsch 2003 7

Using particle diagrams to represent elements, compounds and mixtures.

Element

Diatomic element

Compound

Mixture

J Deutsch 2003 8

Regents Question: 08/02 #6

Which species represents a chemical compound?

(1) N2 (3) Na

(2) NH4+ (4) NaHCO3

Compounds are made up of more than one type of element. (Look for more than one capital letter.)

Compounds are electrically neutral.

J Deutsch 2003 9

Which substance can be decomposed by a chemical change?

(1) Co

(2) CO

(3) Cr

(4) Cu

J Deutsch 2003 10

Mixtures are composed of two or more different substances that can be separated by physical means.

J Deutsch 2003 11

J Deutsch 2003 12

Regents Question: 08/02 #51On a field trip, Student X and Student Y collected two

rock samples. Analysis revealed that both rocks contained lead and sulfur. One rock contained a certain percentage of lead and sulfur by mass, and the other rock contained a different percentage of lead and sulfur by mass. Student X stated that the rocks contained two different mixtures of lead and sulfur. Student Y stated that the rocks contained two different compounds of lead and sulfur. Their teacher stated that both students could be correct.

Draw particle diagrams in each of the rock diagrams provided in your answer booklet to show how Student X’s and Student Y’s explanations could both be correct. Use the symbols in the key provided in your answer booklet to sketch lead and sulfur atoms.

J Deutsch 2003 13

Regents Question: 08/02 #51 AnswerDraw particle diagrams in each of the rock diagrams provided in your answer booklet to show how Student X’s and Student Y’s explanations could both be correct. Use the symbols in the key provided in your answer booklet to sketch lead and sulfur atoms.

Student X

Student Y

Rock A Rock B

J Deutsch 2003 14

When different substances are mixed together, a homogeneous or heterogeneous mixture is formed. (3.1s)

A homogeneous mixture is called a solution

A solution in which something is dissolved in water is called an aqueous solution

NaCl(aq) means that sodium chloride (table salt) is dissolved in water and is therefore a homogenous mixture. (aq) stands for aqueous

An alloy is a solution of metals eg. brass, bronze

J Deutsch 2003 15

Which of these terms refers to matter that could be heterogeneous?

(1) element

(2) mixture

(3) compound

(4) solution

J Deutsch 2003 16

The proportions of components in a mixture can be varied. Each component in a mixture retains its original properties. (3.1t)

Two mixtures of Hydrogen (H2) and Neon (Ne)

J Deutsch 2003 17

Differences in properties such as density, particle size, molecular polarity, boiling point and freezing point, and solubility permit physical separation of the components of the mixture. (3.1nn)

Chromatography, Filtration, Dissolving, Distillation, Crystallization

Density and polarity Particle Size solubility

Boiling Point Freezing Point

J Deutsch 2003 18

Regents Question: 01/04 #12A bottle of rubbing alcohol contains both 2-

propanol and water. These liquids can be separated by the process of distillation because the 2-propanol and water

(1) have combined chemically and retain their different boiling points

(2) have combined chemically and have the same boiling point

(3) have combined physically and retain the different boiling points

(4) have combined physically and have the same boiling point

J Deutsch 2003 19

Particle size

Boiling point

Density and polarity

J Deutsch 2003 20

A solution is a homogeneous mixture of a solute dissolved in a solvent. The solubility of a solute in a given amount of solvent is dependent on the temperature, the pressure, and the chemical natures of the solute and solvent. (3.1oo)

Dissolved particles are too small to be trapped by a filter

J Deutsch 2003 21

Regents Question: 08/02 #7Which mixture can be separated by using the

equipment shown?

(1) NaCl(aq) and SiO2(s)

(2) NaCl(aq) and C6H12O6(aq)

(3) CO2(aq) and NaCl(aq)

(4) CO2(aq) and C6H12O6(aq)(aq) stands for aqueous which means dissolved in water.

Dissolved particles are too small to be trapped by the filter.

J Deutsch 2003 22

Solubility of a nonvolatile solute depends on temperature. Solubility is the maximum amount of solute that a

solvent can hold at a given temperature.– An unsaturated solution is one in which the solvent

can dissolve more solute– A saturated solution is one in which the solvent has as

much solute as it can hold– A supersaturated solution is one in which there is

more solute dissolved than a solvent can normally hold.• Make a supersaturated solution by cooling a saturated solution• Supersaturated solutions are unstable and will precipitate the

excess solute when a seed crystal is added.

As temperature increases, solubility of a solid increases.

J Deutsch 2003 23

Table G shows the solubilities of some gases and some solids at various temperatures when dissolved in 100 grams of water.

J Deutsch 2003 24

•A solution which is on the line is saturated

•A solution below the line is unsaturated

•A solution above the line is supersaturated

J Deutsch 2003 25

Add a test crystal to see if a solution is unsaturated, saturated or supersaturated.

Unsaturated – the test crystal dissolves Saturated – the test crystal settles to the

bottom Supersaturated – a large amount of crystals

precipitate from the solution

J Deutsch 2003 26

According to Reference Table G, which solution is saturated at 30°C?

(1) 12 grams of KClO3 in 100 grams of water

(2) 12 grams of KClO3 in 200 grams of water

(3) 30 grams of NaCl in 100 grams of water

(4) 30 grams of NaCl in 200 grams of water

J Deutsch 2003 27

The solubility of a gas depends on temperature and pressure.

As temperature increases, the solubility of a gas decreases

As pressure increases, the solubility of a gas increases

J Deutsch 2003 28

Which are gases?

J Deutsch 2003 29

One hundred grams of water is saturated with NH4Cl at 50°C. According to Table G, if the temperature is lowered to 10°C, what is the total amount of NH4Cl that will precipitate?

(1) 5.0 g (3) 30. g

(2) 17 g (4) 50. g

J Deutsch 2003 30

Regents Question: 01/03 #65-66

When cola, a type of soda pop, is manufactured, CO2 (g) is dissolved in it.

A capped bottle of cola contains CO2 (g) under high pressure. When the cap is removed, how does pressure affect the solubility of the dissolved CO2 (g)?

A glass of cold cola is left to stand 5 minutes at room temperature. How does temperature affect the solubility of the CO2 (g)?

As the pressure decreases, the solubility decreases.

As the temperature increases, the solubility decreases.

J Deutsch 2003 31

Oil and water are not miscible Like dissolves like (charged

solutes dissolve in charged solvents, uncharged solutes dissolve in uncharged solvents)– Nonpolar solutes dissolve in

nonpolar solvents– Polar solutes dissolve in polar

solvents – Ionic solutes dissolve in polar

solvents

Dry cleaners use a nonpolar solvent to get rid of oil and grease

Liquids that dissolve each other are called miscible liquids.

(Polar)

(Nonpolar)

J Deutsch 2003 32

Hexane (C 6 H 14 ) and water do not form a solution. Which statement explains this phenomenon?

(1) Hexane is polar and water is nonpolar.

(2) Hexane is ionic and water is polar.

(3) Hexane is nonpolar and water is polar.

(4) Hexane is nonpolar and water is ionic.

J Deutsch 2003 33

Solubility Guidelines

Not all substances are soluble in water Reference Table F lists solubility rules and

exceptions to those rules.

J Deutsch 2003 34

Soluble Not Soluble

J Deutsch 2003 35

Which of the following compounds is least soluble

in water?

(1) copper (II) chloride

(2) aluminum acetate

(3) iron (III) hydroxide

(4) potassium sulfate

J Deutsch 2003 36

According to Table F, which of these salts is least soluble in water?

(1)LiCl

(2) RbCl

(3) FeCl2

(4) PbCl2

J Deutsch 2003 37

The concentration of a solution may be expressed as molarity (M), percent by volume, percent by mass, or parts per million (ppm). (3.1pp)

Molarity Percent by mass Parts per MillionM = moles solute % = grams solute x 100 ppm = grams solute x 1,000,000

Liters solution Grams solution Grams solution

Percent by volume% = liters solute x 100

Liters solution

J Deutsch 2003 38

What is the molarity of a solution that contains 0.50 mole of NaOH in 0.50 liter of solution?

(1) 1.0 M (3) 0.25 M

(2) 2.0 M (4) 0.50 M

Molarity = Moles

Liters

J Deutsch 2003 39

How many moles of solute are contained in 200 milliliters of a 1 M solution?

(1) 1 (3) 0.8

(2) 0.2 (4) 200

J Deutsch 2003 40

What is the total number of grams of NaI(s) needed to make 1.0 liter of a 0.010 M solution?

(1) 0.015 (3) 1.5

(2) 0.15 (4) 15Na 1 x 23.0 = 23.0

I 1 x 126.9 = 126.9

149.9 g / mole

Molarity = moles

liters

0.010M = x 1.0 L

X = 0.010 moles 0.010 moles x 149.9 g/mole =

J Deutsch 2003 41

Solubility data for four different salts in water at 60°C are shown in the table below. Which salt is most soluble at 60°C?

(1) A (2) B (3) C (4) D

Salt Solubility in Water at 60 °C

A - 10 grams /50 grams H2O

B - 20 grams /60 grams H2O

C - 30 grams /120 grams H2O

D - 40 grams/80 grams H2O

J Deutsch 2003 42

Regents Question: 01/04 #56-58A student uses 200 grams of water at a

temperature of 60°C to prepare a saturated solution of potassium chloride, KCl.

Identify the solute in this solution.

According to Reference Table G, how many grams of KCl must be used to create this saturated solution?

This solution is cooled to 10°C and the excess KCl precipitates (settles out). The resulting solution is saturated at 10°C. How many grams of KCl precipitated out of the original solution?

Hint: 200 g of water was used – table G is for 100 g of water

J Deutsch 2003 43

The addition of a nonvolatile solute to a solvent causes the boiling point of the solvent to increase and the freezing point of the solvent to decrease. The greater the concentration of particles, the greater the effect. (3.1qq)

Solute Moles of particles per mole of solute

C6H12O6 1 (Non-electrolytes do not separate into ions)

NaCl 2 (1-Na+ and 1 Cl-)

CaF2 3 (1-Ca2+ and 2 F-)

H2SO4 3 (2-H+ and 1 SO42-)

J Deutsch 2003 44

At standard pressure when NaCl is added to water, the solution will have a

(1) higher freezing point and a lower boiling point than water

(2) higher freezing point and a higher boiling point than water

(3) lower freezing point and a higher boiling point than water

(4) lower freezing point and a lower boiling point than water

J Deutsch 2003 45

The three phases of matter (solids, liquids, and gases) have different properties. (3.1kk)

Solid Liquid Gas

J Deutsch 2003 46

Properties of Solids

Regular geometric pattern in the arrangement of the molecules called a crystal lattice

Molecules are close together and vibrate in place Molecules do not move from place to place Solids are not compressible Definite shape and definite volume

J Deutsch 2003 47

Properties of Liquids

Molecules can move around (fluid) Molecules are farther apart than in a solid Liquids take the shape of their container Not compressible No definite shape but do have

definite volume

The forces of attraction between the molecules are weaker in a liquid than they are in a solid.

J Deutsch 2003 48

Properties of Gases

Molecules fill their container (spread out) Molecules are very far apart Molecules move in straight lines until they

hit something (another molecule or wall of the container)

No definite shape and no definite volume

The forces of attraction between the molecules are very weak.

J Deutsch 2003 49

Which statement correctly describes a sample of gas confined in a sealed container?

(1) It always has a definite volume, and it takes the shape of the container.

(2) It takes the shape and the volume of any container in which it is confined.

(3) It has a crystalline structure.

(4) It consists of particles arranged in a regular geometric pattern.

J Deutsch 2003 50

Which 5.0-milliliter sample of NH3 will take the shape of and completely fill a closed 100.0-milliliter container?

(1) NH3 (s) (3) NH3 (g)

(2) NH3 (l) (4)NH3 (aq)

J Deutsch 2003 51

In which material are the particles arranged in a regular geometric pattern?

(1) CO2 (g)

(2) NaCl(aq)

(3) H2O(l)

(4) C12H22O11 (s)

J Deutsch 2003 52

Energy can exist in different forms, such as chemical, electrical, electromagnetic, thermal, mechanical, and nuclear. (4.1a)

Kinetic energy – the energy of motion

Potential energy – the energy of position (stored energy)

J Deutsch 2003 53

The amount of thermal energy contained in the molecules depends on how fast they are moving and how many molecules there are. The total kinetic energy of all the molecules

combined is called thermal energy Thermal energy is a result of the Kinetic Energy of

the molecules’ motion (molecules are always moving.)

Which can melt more ice: a small cup of hot water or a swimming pool of cold water?

J Deutsch 2003 54

Heat is a transfer of energy (usually thermal energy) from a body of higher temperature to a body of lower temperature. Thermal energy is the energy associated with the random motion of atoms and molecules. (4.2a)The Law of Conservation of Energy states that energy can neither be created nor destroyed.

J Deutsch 2003 55

Heat is transferred to different materials at different rates.

The specific heat capacity (C) determines the rate at which heat will be absorbed.

The specific heat capacity for water is 4.18J/g

The quantity of heat absorbed (Q) can be calculated by: Q=mCTm=mass T=change in temperature

J Deutsch 2003 56

Temperature is a measurement of the average kinetic energy of the particles in a sample of material.

Temperature is not a form of energy. (4.2b)Two temperature scales used in chemistry are Celsius and Absolute

The unit of temperature in the Celsius scale is the degree (ºC)

The unit of temperature on the Absolute scale is the Kelvin (K)

J Deutsch 2003 57

Which change in the temperature of a 1-gram sample of water would cause the greatest increase in the average kinetic energy of its molecules?

(1) 1°C to 10°C (3) 50°C to 60°C

(2) 10°C to 1°C (4) 60°C to 50°C

J Deutsch 2003 58

To convert between absolute and Celsius temperature scales use K=ºC+273

J Deutsch 2003 59

Kinetic molecular theory (KMT) for an ideal gas states that all gas particles (3.4b): 1. are in random, constant, straight-line

motion. 2. are separated by great distances relative

to their size; the volume of the gas particles is considered negligible.

3. have no attractive forces between them. 4. have collisions that may result in the

transfer of energy between gas particles, but the total energy of the system remains constant.

J Deutsch 2003 60

The concept of an ideal gas is a model to explain the behavior of gases. A real gas is most like an ideal gas when the real gas is at low pressure and high temperature. (3.4a)

Molecules are far apart and moving very fast!

J Deutsch 2003 61

Real Gases Molecules do take up space Molecules do attract each other Energy is lost during collisions Under conditions of high temperature and

low pressure, real gases behave more like ideal gases

Small molecules take up little space and have weaker forces of attraction and are closer to an ideal gas

Hydrogen and helium are closest to being ideal gases

J Deutsch 2003 62

Kinetic molecular theory describes the relationships of pressure, volume, temperature, velocity, and frequency and force of collisions among gas molecules. (3.4c)

P1V1 P2V2

J Deutsch 2003 63

Ideal Gas Laws

Boyle’s Law– Indirect Relationship

between pressure and volume

– Temperature remains constant

– PxV = constant

Charles’ law– Direct relationship

between volume and temperature

– Pressure remains constant

– V/T = constant

– Temperature must be Absolute temperature (Kelvins)

J Deutsch 2003 64

Graphing the gas laws

Volume

Temperature

Pressure

Volume

Temperature

PressureAs absolute temperature increases, pressure increases at constant volume

As absolute temperature increases, volume increases at constant pressure

As pressure increases, volume decreases at constant temperature

J Deutsch 2003 65

Regents Question: 06/02 #14Which graph shows the pressure-temperature

relationship expected for an ideal gas?

J Deutsch 2003 66

Equal volumes of different gases at the same temperature and pressure contain an equal number of particles. (3.4e)

Avogadro’s Hypothesis

J Deutsch 2003 67

At the same temperature and pressure, which sample contains the same number of moles of particles as 1 liter of O2 (g)?

(1) 1 L Ne(g) (3) 0.5 L SO2 (g)

(2) 2 L N2 (g) (4) 1 L H2O(l)

J Deutsch 2003 68

The concepts of kinetic and potential energy can be used to explain physical processes that include: fusion (melting), solidification (freezing), vaporization (boiling, evaporation), condensation, sublimation, and deposition. (4.2c)Add energy

(endothermic) subliming

melting boiling

SOLID LIQUID GAS

Remove energy

(exothermic)freezing

depositing

condensing

J Deutsch 2003 69

Which change is exothermic?

(1) freezing of water

(2) melting of iron

(3) vaporization of ethanol

(4) sublimation of iodine

J Deutsch 2003 70

A change in phase is a change in Potential Energy, not Kinetic Energy

Potential energy changes so temperature

doesn’t

Boiling Point

Melting Point

J Deutsch 2003 71

Energy and phase changes

AB - solid warms up (KE inc/PE constant)

BC- solid melts (KE constant/PE inc)

CD – liquid warms up (KE inc/PE constant)

DE- liquid boils (KE constant/PE inc)

EF – gas warms (KE inc/PE constant)

J Deutsch 2003 72

As ice melts at standard pressure, its temperature remains at 0°C until it has completely melted. Its potential energy

(1) decreases

(2) increases

(3) remains the same

J Deutsch 2003 73

Regents Question: 08/02 #54A sample of water is heated from a liquid at 40°C

to a gas at 110°C. The graph of the heating curve is shown in your answer booklet.

a On the heating curve diagram provided in your answer booklet, label each of the following regions:

Liquid, only Gas, only Phase change

Liquid Only

Gas OnlyPhase change

J Deutsch 2003 74

Regents Question: cont’db For section QR of the graph, state what is

happening to the water molecules as heat is added.

c For section RS of the graph, state what is happening to the water molecules as heat is added.

They move faster, their temperature increases.

Their intermolecular bonds are breaking, their potential

energy is increasing.

J Deutsch 2003 75

What is the melting point of this substance?

(1) 30°C (3) 90°C

(2) 55°C (4) 120°C

J Deutsch 2003 76

The quantity of energy absorbed or released during a phase change can be calculated using the Heat of Fusion or Heat of Vaporization

Melting (fusion) or freezing (solidification)– Q=mHf where Hf is the heat of fusion

(for water: 333.6 J/g) Boiling (vaporization) or condensing

– Q=mHv where Hv is the heat of vaporization (for water: 2259 J/g)

Hf and Hv are given to Table B – m is the mass

J Deutsch 2003 77

In which equation does the term “heat” represent heat of fusion?

(1) NaCl(s) + heat NaCl(l)

(2) NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)+ heat

(3) H2O(l)+ heat H2O(g)

(4) H2O(l)+ HCl(g) H3O+(aq) + Cl –(aq) + heat

Fusion refers to melting.

J Deutsch 2003 78

Melting Point

The temperature at which a liquid and a solid are in equilibrium

The melting point for ice is 0ºC The melting point of a substance is the

same as its freezing point

J Deutsch 2003 79

Given the equation: H2O(s) H2O(l)

At which temperature will equilibrium exist when the atmospheric pressure is 1 atm?

(1) 0 K (3) 273 K

(2) 100 K (4) 373 K

K=C + 273

J Deutsch 2003 80

The solid and liquid phases of water can exist in a state of equilibrium at 1 atmosphere of pressure and a temperature of

(1) 0°C (3) 273°C

(2) 100°C (4) 373°C

J Deutsch 2003 81

The freezing point of bromine is

(1) 539°C

(2) –539°C

(3) 7°C

(4) –7°C

See Table S

Melting point is the same as freezing point

Convert K to C (K=C+273)

J Deutsch 2003 82

A physical change results in the rearrangement of existing particles in a substance. A chemical change results in the formation of different substances with changed properties. (3.2a) Physical Changes

– Changes in phase• Melting

• Boiling

• Subliming

– Dissolving

Chemical Changes– Any chemical reaction

• Synthesis• Decomposion• Single Replacment• Double Replacement• Combustion (burning)

J Deutsch 2003 83

Which type of change must occur to form a compound?

(1) chemical

(2) physical

(3) nuclear

(4) phase

J Deutsch 2003 84

Chemical and physical changes can be exothermic or endothermic. (4.1b) Exothermic

– Potential energy decreases

– Releases energy H is negative

– Energy is on the right2H2 + O2 2H2O + energy

Endothermic– Potential energy

increases

– Absorbs energy H is positive

– Energy is on the left2H2O + energy 2H2 + O2

J Deutsch 2003 85

Regents Question: 06/02 #64-66A hot pack contains chemicals that can be

activated to produce heat. A cold pack contains chemicals that feel cold when activated.

• Based on energy flow, state the type of chemical change that occurs in a hot pack.

• A cold pack is placed on an injured leg. Indicate the direction of the flow of energy between the leg and the cold pack.

• What is the Law of Conservation of Energy? Describe how the Law of Conservation of Energy applies to the chemical reaction that occurs in the hot pack.

Exothermic

From the leg to the cold pack (Hot to Cold)

Energy cannot be created nor destroyed. It can only be changed from one form to another. The heat produced in the hot pack was stored in the chemical bonds.

J Deutsch 2003 86

According to Table I, which potential energy diagram best represents the reaction that forms H2O(l) from its elements?

J Deutsch 2003 87

Activation Energy (Ea) is the energy

needed to get a reaction started (reach the activated complex).

J Deutsch 2003 88

Enthalpy (H) The heat of reaction H=PE products – PE reactants

The value for H is the same in the forward and the reverse reaction. Only the sign is changed.

Measured in kJ (kilojoules) + H – Endothermic – Energy absorbed - H – Exothermic – Energy released The large the value of H, the more energy

absorbed or released Reference Table I gives H for many reactions

J Deutsch 2003 89

Given the reaction:

CH4 (g) + 2 O2 (g) 2 H2O(g) + CO2 (g)

What is the overall result when CH4 (g) burns according to this reaction?

(1) Energy is absorbed and H is negative.

(2) Energy is absorbed and H is positive.

(3) Energy is released and H is negative.

(4) Energy is released and H is positive.

J Deutsch 2003 90

According to Table I, which salt releases energy as it dissolves?

(1) KNO3 (3) NH4NO3

(2) LiBr (4) NaCl

J Deutsch 2003 91

Given the reaction:

2 H2 (g) + O2 (g) 2 H2O(l) + 571.6 kJ

What is the approximate H for the formation of 1 mole of H2O(l)?

(1) –285.8 kJ (3) –571.6 kJ

(2) +285.8 kJ (4) +571.6 kJ

J Deutsch 2003 92

A catalyst lowers the activation energy to speed up a reaction

Activated Complex With Catalyst

J Deutsch 2003 93

Regents Question: 06/02 #55-56Given the

reaction:

A + B C

• Does the diagram illustrate an exothermic or an endothermic reaction? •State one reason, in terms of energy, to support your

answer.

• On the diagram provided in your answer booklet, draw a dashed line to indicate a potential energy curve for the reaction if a catalyst is added.

Endothermic

The potential energy of the products is higher than the reactants, Energy is absorbed.

J Deutsch 2003 94

The structure and arrangement of particles and their interactions determine the physical state of a substance at a given temperature and pressure. (3.1jj)

Solid Liquid Gas

J Deutsch 2003 95

Intermolecular forces created by the unequal distribution of charge result in varying degrees of attraction between molecules. Hydrogen bonding is an example of a strong intermolecular force. (5.2m)

Dipole-Dipole attraction between polar molecules

J Deutsch 2003 96

Hydrogen bonds occur when hydrogen is bonded to a small, highly electronegative atom.N, O and F can have hydrogen bonds when hydrogen is bonded to it.Account for the unusual properties of water:High boiling point, surface tension, six sided snowflake

J Deutsch 2003 97

Physical properties of substances can be explained in terms of chemical bonds and intermolecular forces.

•Ionic bonds are strong

•Hydrogen bonds are strong intermolecular forces

•Polar molecules exhibit attraction between the + and – sides of their molecules

•Bonds between nonpolar molecules are weak. The more protons in the molecule, the stronger these forces.

J Deutsch 2003 98

The strongest forces of attraction occur between

molecules of

(1) HCl (3) HBr

(2) HF (4) HI

J Deutsch 2003 99

These properties include conductivity, malleability, solubility, hardness, melting point, and boiling point. (5.2n) The stronger the intermolecular forces, the

higher the boiling point and melting point. The stronger the intermolecular forces, the

lower the vapor pressure.– See Table H

J Deutsch 2003 100

Table H – the vapor pressure of four liquids at various temperatures.

As temp inc, vapor pressure inc.

J Deutsch 2003 101

According to Reference Table H, what is the vapor pressure of propanone at 45°C?

(1)22 kPa

(2)33 kPa

(3)70. kPa

(4) 98 kPa

J Deutsch 2003 102

A liquid will boil when its vapor pressure equals the atmospheric pressure.

Raising the temperature will increase the vapor pressure of the liquid

Lowering the atmospheric pressure will lower the boiling point– On top of a high mountain, water boils at a

temperature below 100C

J Deutsch 2003 103

Standard pressure is 101.3 kilopascals (kPa) or 1 atmoshpere (atm)The normal boiling point occurs when the atmospheric pressure is 101.3 kPa (standard pressure)

The normal boiling point of ethanol is 80ºC.

J Deutsch 2003 104

As the pressure on the surface of a liquid decreases, the temperature at which the liquid will boil

(1) decreases

(2) increases

J Deutsch 2003 105

As the temperature of a liquid increases, its vapor pressure

(1) decreases

(2) increases

J Deutsch 2003 106

The vapor pressure of a liquid is 0.92 atm at 60°C. The normal boiling point of the liquid could be

(1) 35°C (3) 55°C

(2) 45°C (4) 65°C

The normal boiling point is the temperature at which a liquid boils when the atmospheric pressure

is standard pressure (1 atm or 101.3 kPa)

J Deutsch 2003 107

Regents Question: 01/03 #68What is the vapor pressure of liquid A at 70°C?

Your answer must include correct units.700 mm Hg

J Deutsch 2003 108

Regents Question: 01/03 #69At what temperature does liquid B have the

same vapor pressure as liquid A at 70°C?

Your answer must include correct units. 113°C

J Deutsch 2003 109

Regents Question: 01/03 #70Which liquid will evaporate more rapidly? Explain

your answer in terms of intermolecular forces.Liquid A will evaporate more rapidly because, at any temperature, it has the weaker intermolecular forces.

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