UNIT 2 UNIT 2 CHEMISTRYCHEMISTRY

Chapter 5 Chapter 5 I. Properties and ChangesI. Properties and Changes

Note: Good scientists are questioning, Note: Good scientists are questioning, sceptical, persistent & honestsceptical, persistent & honest

The Particle Theory of MatterThe Particle Theory of Matter All matter is made up of extremely tiny All matter is made up of extremely tiny

particles called atomsparticles called atoms Each pure substance has its own kind of Each pure substance has its own kind of

particle, different from the particles of other particle, different from the particles of other pure substancespure substances

Particles attract each other.Particles attract each other.

Particles are always movingParticles are always moving Particles at a higher temperature move Particles at a higher temperature move

faster (on average) than particles at a faster (on average) than particles at a lower temperaturelower temperature

Scientific Model Scientific Model – any understanding that allows a scientist any understanding that allows a scientist

to picture the processes of nature that to picture the processes of nature that cannot be simply or directly seen.cannot be simply or directly seen.

Example – Particle Theory of MatterExample – Particle Theory of Matter– points a & b: what matter looks likepoints a & b: what matter looks like– Points c-e: how matter behavesPoints c-e: how matter behaves

See bottom of page 156 See bottom of page 156

II. II. A Matter of Behavior - MixturesA Matter of Behavior - Mixtures

In nature particles may be mixed in different ways.In nature particles may be mixed in different ways.

A mixture is a substance that contains A mixture is a substance that contains more that one type of particle.more that one type of particle.

Mechanical Mixtures (Heterogenous)Mechanical Mixtures (Heterogenous)– Mixtures in which particles are not evenly Mixtures in which particles are not evenly

scattered. All parts can be seen.scattered. All parts can be seen.

E.g. raisin bran, trail mix, gravel, etc.E.g. raisin bran, trail mix, gravel, etc.

Solutions (Homogenous)Solutions (Homogenous)– Mixtures in which types of particles are Mixtures in which types of particles are

evenly scattered. One type of particle evenly scattered. One type of particle (solute) is dissolved in the other (solvent) (solute) is dissolved in the other (solvent) material. Not all parts can be seen.material. Not all parts can be seen.

– E.g.. Salt waterE.g.. Salt water Pure SubstancesPure Substances

– Contain only one type of particleContain only one type of particle– Includes elements and compoundsIncludes elements and compoundsE.g. water, oxygen, etc.E.g. water, oxygen, etc.

III. Changes In MatterIII. Changes In Matter

Physical ChangesPhysical Changes A change in the substance but no new A change in the substance but no new

substance is formedsubstance is formed They are often reversibleThey are often reversible

E.g.. Phase Changes – solid, liquid & gasE.g.. Phase Changes – solid, liquid & gas Change in shape – cutting or bendingChange in shape – cutting or bending

Chemical ChangesChemical Changes A change in a substance(s) in which at A change in a substance(s) in which at

least one new substance (with new least one new substance (with new properties) is formed. properties) is formed.

Often difficult or impossible to reverseOften difficult or impossible to reverse

E.g. – Burning paper, electrolysis of water to E.g. – Burning paper, electrolysis of water to form Hform H22 and O and O22

Physical PropertiesPhysical Properties– Can be observed or measured without a Can be observed or measured without a

chemical change happeningchemical change happening

E.g. phase, color, temperature, density (d = E.g. phase, color, temperature, density (d = m/v)m/v)

Chemical PropertiesChemical Properties– Can be observed only during a chemical Can be observed only during a chemical

change.change.

E.g. combustabilityE.g. combustability

Qualitative PropertyQualitative Property Describes the quality of a property Describes the quality of a property Cannot be measuredCannot be measured

E.g. smells really bad, a yellow solidE.g. smells really bad, a yellow solid

Quantitative PropertyQuantitative Property1.1. Describes a property using a numberDescribes a property using a number

E.g. volume, mass, density, freezing point, E.g. volume, mass, density, freezing point, melting pointmelting point

See Table 5.2 on page 164See Table 5.2 on page 164

Evidence of Chemical ChangeEvidence of Chemical Change Heat is produced or absorbed.Heat is produced or absorbed. The starting material is used up.The starting material is used up. A change in color.A change in color. A material with new properties forms.A material with new properties forms. Gas bubbles form.Gas bubbles form. Grains of a solid (precipitate) form when Grains of a solid (precipitate) form when

2 liquids are mixed.2 liquids are mixed.

Changes of State

The changes on this side use energy. The changes on this side give off energy

GAS

SOLID

LIQUID

Activities/AssignmentActivities/Assignment

– Teacher DemonstrationTeacher Demonstration– SteamboatSteamboat– Investigation 5-A, page 160-161Investigation 5-A, page 160-161

– Read pages 152-169 and do CYU on page Read pages 152-169 and do CYU on page 169 1-4169 1-4

– AIMS #1AIMS #1

IV. Historical Ideas About the IV. Historical Ideas About the Nature of MatterNature of Matter

Ancient Greek Philosophers Ancient Greek Philosophers (500 B.C.E.)(500 B.C.E.) Wondered why matter behaves as it does Wondered why matter behaves as it does Manipulated ideas in their minds but did no Manipulated ideas in their minds but did no

experimentsexperiments

c) Empidocles proposed that matter was composed of four elements: earth, water, air & fire

d) Democritus suggested that matter was made of tiny particles that could not be broken down further. He called these particles “atomos,” which means indivisible.

Cutting the Cheese

This model was later rejected by Aristotle This model was later rejected by Aristotle and Socrates and predominant thinking and Socrates and predominant thinking went back to the four element theory. went back to the four element theory. This lasted for the next 2000 years.This lasted for the next 2000 years.

Alchemists Alchemists (500-1600 A.C.E.)(500-1600 A.C.E.) First people to perform hands-First people to perform hands-

on experiments.on experiments. They were part They were part pharmacist, part mystic and pharmacist, part mystic and secretive. secretive.

  Three main beliefsThree main beliefs– Some elements could be changed Some elements could be changed

into others (especially into goldinto others (especially into gold– There was a substance that would There was a substance that would

grant eternal lifegrant eternal life– They could produce a universal They could produce a universal

solvent that could dissolve all solvent that could dissolve all substancessubstances

Modern Chemists Modern Chemists (1600-Present)(1600-Present) Sir Francis Bacon Sir Francis Bacon (1561-1626)(1561-1626)

– contributed the scientific method.contributed the scientific method.– argued that science should be based on argued that science should be based on

the basis of experimental knowledge the basis of experimental knowledge rather than speculation.rather than speculation.

Robert Boyle Robert Boyle (1627-1691)(1627-1691) – 1661 published “The Skeptical 1661 published “The Skeptical

Chymist” wrote about elements as Chymist” wrote about elements as being being “unmingled bodies.”“unmingled bodies.”

– Recognized that elements could be Recognized that elements could be combined to form compounds.combined to form compounds.

– But didn't know which materials were But didn't know which materials were which.which.

Joseph Priestly Joseph Priestly (late 1700’s)(late 1700’s) First person to isolate oxygen First person to isolate oxygen

scientificallyscientifically He didn’t know it was an elementHe didn’t know it was an element

Antoine de Lavoisier Antoine de Lavoisier (1743-1794)(1743-1794) defined elements as “pure substances defined elements as “pure substances

that cannot be chemically broken down that cannot be chemically broken down into simpler substances. (We still use this into simpler substances. (We still use this definition today.)definition today.)

Discovered and identified 23 elements Discovered and identified 23 elements based on careful measurement.based on careful measurement.

Identified air as a mixture of oxygen and Identified air as a mixture of oxygen and some other gas. some other gas.

V. Models of Atomic StructureV. Models of Atomic Structure

1.1. Dalton’s “Billiard Ball” Model Dalton’s “Billiard Ball” Model (early (early 1800’s) page 183 1800’s) page 183

All elements are composed of atoms. All elements are composed of atoms. Atoms are solid, indivisible & indestructible Atoms are solid, indivisible & indestructible particles.particles.

Atoms cannot be created nor destroyed in a Atoms cannot be created nor destroyed in a chemical reaction. chemical reaction.

All atoms of the same element are identical All atoms of the same element are identical in mass and size, but they are different in in mass and size, but they are different in mass and size from the atoms of other mass and size from the atoms of other elements.elements.

Compounds are created when atoms of Compounds are created when atoms of different elements link together in definite different elements link together in definite proportions.proportions.

Dalton’s Atomic Theory (cont’d)Dalton’s Atomic Theory (cont’d)

2.2. Thomson’s “Raisin Bun” Model of the Thomson’s “Raisin Bun” Model of the Atom Atom (1904)(1904)

Discovered electrons (very light Discovered electrons (very light negative particles) through negative particles) through experiments that involved passing an experiments that involved passing an electrical current through a gas. electrical current through a gas.

This disproved Dalton’s theory that the This disproved Dalton’s theory that the atom was indivisible.atom was indivisible.

Discovered protons (heavier positive Discovered protons (heavier positive particles)later using more advanced particles)later using more advanced apparatus.apparatus.

Thomson proposed the following:Thomson proposed the following: Electrons have a small mass and a Electrons have a small mass and a

negative chargenegative charge An atom is a sphere of positive electricityAn atom is a sphere of positive electricity Negative electrons are embedded in the Negative electrons are embedded in the

positive sphere, so that the resulting positive sphere, so that the resulting atom is neutral or uncharged.atom is neutral or uncharged.

3.3. Rutherford’s “Nuclear” ModelRutherford’s “Nuclear” Model Shot Helium alpha

particles (a type of radiation) through gold foil to test Thomson’s model and discovered a dense, positively charged core in the atom called the nucleus.

gold foil

helium nuclei

He found that while most of the helium nuclei passed

through the foil, a small number were deflected and, to

their surprise, some helium nuclei bounced straight

back.

helium nuclei

He proposedHe proposed The nucleus is a very tiny, dense, and The nucleus is a very tiny, dense, and

positively charged core of an atom.positively charged core of an atom. All of the atom’s positively charged All of the atom’s positively charged

particles, called protons, are contained in particles, called protons, are contained in the nucleus.the nucleus.

The nucleus is surrounded by mostly The nucleus is surrounded by mostly empty space.empty space.

Rapidly moving, negatively charged Rapidly moving, negatively charged electrons are scattered outside the electrons are scattered outside the nucleus around the atom’s edge in what nucleus around the atom’s edge in what is referred to as an electron cloud.is referred to as an electron cloud.

Improved on Improved on Rutherford’s Rutherford’s model by model by placing placing electrons in electrons in specific orbits specific orbits about the about the nucleus.nucleus.

4.4. Bohr’s “Planetary” Model Bohr’s “Planetary” Model (1913)(1913)

Bohr’s Atom

electrons in orbits

nucleus

HELIUM ATOM

+N

N

+-

-

proton

electron

neutron

Shell

What do these particles consist of?

He proposed:He proposed: Electrons move around the nucleus in Electrons move around the nucleus in

nearly circular paths called orbits, much nearly circular paths called orbits, much like how planets circle the Sun.like how planets circle the Sun.

Each electron in an orbit has a definite Each electron in an orbit has a definite amount of energy. Electrons can move amount of energy. Electrons can move within these energy levels without loss of within these energy levels without loss of energy.energy.

4.4. Bohr’s “Planetary” Model Bohr’s “Planetary” Model (1913)(1913)

The nucleus is surrounded by mostly The nucleus is surrounded by mostly empty space.empty space.

Rapidly moving, negatively charged Rapidly moving, negatively charged electrons are scattered outside the nucleus electrons are scattered outside the nucleus around the atom’s edge in what is referred around the atom’s edge in what is referred to as an electron cloud.to as an electron cloud.

Bohr’s model Bohr’s model worked well in worked well in explaining the explaining the behaviour of behaviour of simple atoms simple atoms such as such as hydrogen, that hydrogen, that contained few contained few electrons, but it electrons, but it did not explain did not explain the more the more complex atoms.complex atoms.

5.5. Einstein’s Quantum (“Wave”) Model Einstein’s Quantum (“Wave”) Model of the Atom – Quantum Mechanicsof the Atom – Quantum Mechanics

The Quantum Model proposed the The Quantum Model proposed the following:following:

Electrons do not move about the atom’s Electrons do not move about the atom’s nucleus in a definite path like planets nucleus in a definite path like planets around the sun around the sun

It is impossible to determine the exact It is impossible to determine the exact location of an electron.location of an electron.

5.5. Einstein’s Quantum (“Wave”) Model Einstein’s Quantum (“Wave”) Model of the Atom – Quantum Mechanicsof the Atom – Quantum Mechanics

The probable location of an electron is The probable location of an electron is based on its energy.based on its energy.

Energy levels are divided into four Energy levels are divided into four sublevels, and each sublevel is made up of sublevels, and each sublevel is made up of several pairs of electrons called orbitals.several pairs of electrons called orbitals.

Electrons move randomly in electron Electrons move randomly in electron clouds called orbitals.clouds called orbitals.

– AIMS Booklet #3AIMS Booklet #3– Timeline of Atomic Models DiagramsTimeline of Atomic Models Diagrams

AssignmentAssignment

VI.VI. Bohr-Rutherford DiagramsBohr-Rutherford Diagrams

Proton (p) – A positively charged Proton (p) – A positively charged subatomic particle. subatomic particle.

Neutron (n) – a neutrally charged Neutron (n) – a neutrally charged subatomic particle.subatomic particle.– Protons and neutrons make up the nucleus of Protons and neutrons make up the nucleus of

an atom and each one has a mass of an atom and each one has a mass of approximately one atomic unit. approximately one atomic unit.

Electron (e) – a negatively charged Electron (e) – a negatively charged subatomic particle that “orbits” the subatomic particle that “orbits” the nucleus in rings/shells. It has a mass nucleus in rings/shells. It has a mass so small that it generally doesn’t so small that it generally doesn’t count.count.

Atomic mass – the total amount of Atomic mass – the total amount of mass of an atom and is equal to the # mass of an atom and is equal to the # of protons + # of neutrons.of protons + # of neutrons.

Electron Shells Electron Shells The electrons move around the nucleus The electrons move around the nucleus

in orbits called shells. in orbits called shells. The more energy the electron has, the The more energy the electron has, the

further it is from the nucleus.further it is from the nucleus. The shells can hold:The shells can hold:

– K shell = 2 e’sK shell = 2 e’s– L shell = 8 e’sL shell = 8 e’s– M shell = 8 e’s (18 if forced)M shell = 8 e’s (18 if forced)

Drawing Bohr-Rutherford DiagramsDrawing Bohr-Rutherford Diagrams Find the element on the periodic tableFind the element on the periodic table The atomic # = # of p’s = # of e’sThe atomic # = # of p’s = # of e’s Find the atomic mass on the periodic Find the atomic mass on the periodic

table (round off to the nearest whole #)table (round off to the nearest whole #) # of n’s = atomic mass – # of p’s # of n’s = atomic mass – # of p’s Draw the nucleus as a circle with the # of Draw the nucleus as a circle with the # of

p’s and n’s on the insidep’s and n’s on the inside Draw the same number of e’s as p’s Draw the same number of e’s as p’s

placing them in the shells (in pairs)placing them in the shells (in pairs) PracticePractice

AssignmentAssignment

– BLM 7-18BLM 7-18– Bohr-Rutherford Model PracticeBohr-Rutherford Model Practice– Practice QuizPractice Quiz– Bohr-Rutherford diagrams for the first 20 Bohr-Rutherford diagrams for the first 20

elements.elements.– QuizQuiz

VII. The Periodic TableVII. The Periodic Table

HistoryHistory In the 1850s there were about 50 known In the 1850s there were about 50 known

elements. elements. They were named by the people who They were named by the people who

had found them. had found them. The lists were made in alphabetical The lists were made in alphabetical

order. order. Unfortunately that meant reorganizing Unfortunately that meant reorganizing

the entire table when new elements the entire table when new elements were found.were found.

Dmitri MendeleevDmitri Mendeleev Organized elements in groups Organized elements in groups

(families) with similar characteristics.(families) with similar characteristics. He arranged them in columns with the He arranged them in columns with the

lightest first and the heaviest last.lightest first and the heaviest last. Mendeleev’s system allowed the Mendeleev’s system allowed the

periodic table to grow since he could periodic table to grow since he could leave room for the elements that leave room for the elements that seemed to be missing. seemed to be missing.

It also allowed people to “look for” the It also allowed people to “look for” the missing elements.missing elements.

FamiliesFamilies

1.1. Alkali MetalsAlkali Metals very reactive family (1 every reactive family (1 e-- beyond beyond

stability)stability) shiny, ductile, malleableshiny, ductile, malleable solids at room temperaturesolids at room temperature conduct electricity and heatconduct electricity and heat

2.2. Alkaline Earth MetalsAlkaline Earth Metals fairly reactive family (2 efairly reactive family (2 e-- beyond beyond

stability)stability) shiny, ductile, malleableshiny, ductile, malleable solids at room temperaturesolids at room temperature conduct electricity and heatconduct electricity and heat

3.3. HalogensHalogens very reactive family (1 every reactive family (1 e-- short of short of

stability)stability) non-metalnon-metal don’t conduct heat or electricity don’t conduct heat or electricity

wellwell all gases (except bromine) at all gases (except bromine) at

room temperature.room temperature.

4.4. Noble gasesNoble gases completely non-reactive (don’t completely non-reactive (don’t

socialize with other families)socialize with other families) all are gases at room temperatureall are gases at room temperature stable octetstable octet (outer shell) (outer shell) don’t conduct heat or electricitydon’t conduct heat or electricity used in light bulbsused in light bulbs

5.5. Coinage MetalsCoinage Metals

a)a) got their name because early currency got their name because early currency was made from these elementswas made from these elements

b)b) they are all shiny and very malleable they are all shiny and very malleable (hammered) and ductile (stretched into (hammered) and ductile (stretched into wire)wire)

c)c) all are valuableall are valuable

d)d) they occur in their natural forms (earliest they occur in their natural forms (earliest metals discovered)metals discovered)

e)e) they are not very reactivethey are not very reactive

f)f) fairly high melting pointsfairly high melting points

6.6. Transition MetalsTransition Metals Iron & LeadIron & Lead

• Lead has a low BPLead has a low BP• Iron has a high BPIron has a high BP

Patterns in the Periodic TablePatterns in the Periodic Table Metals on the left, non-metals on the Metals on the left, non-metals on the

rightright atomic number increases left to rightatomic number increases left to right atomic mass increases down a groupatomic mass increases down a group elements in a period (row) have same elements in a period (row) have same

number of electron shellsnumber of electron shells elements in a group have same number elements in a group have same number

of valence (outer shell) electrons (eof valence (outer shell) electrons (e --)) outer families are more reactive (except outer families are more reactive (except

noble gases)noble gases)

AssignmentAssignment

• AIMS #2 & #4AIMS #2 & #4• Crosswords 1 & 2Crosswords 1 & 2• Elementary My Dear WatsonElementary My Dear Watson

VIII. Atoms vs. IonsVIII. Atoms vs. Ions

AtomsAtoms # of protons = # of electrons# of protons = # of electrons neutral chargeneutral charge are ‘happiest’ when they have full valence are ‘happiest’ when they have full valence

shells or empty valence shells. They are shells or empty valence shells. They are very dissatisfied very dissatisfied if if they “don’t quite have a they “don’t quite have a full shell”full shell”

IonsIons atoms which have gained or lost atoms which have gained or lost

electrons to get a full or empty valence electrons to get a full or empty valence shell.shell.

have charges on them. (electrons are have charges on them. (electrons are negative!) negative!)

MetaMetaLLs s LLose electrons to get empty ose electrons to get empty valence shells. They become positive ions.valence shells. They become positive ions.

Eg) Alkali Metals like Na lose 1 eEg) Alkali Metals like Na lose 1 e-- and become and become NaNa1+1+

Eg) Alkaline Earth Metals like Mg lose 2 eEg) Alkaline Earth Metals like Mg lose 2 e-- and and become Mg become Mg 2+2+

Na atom

+++++ - - - - -

++++++ - - - - - -

Na+Na+ ion

+++++ - - - - -

++++++ - - - - - -

Non-metals gain electrons to get full Non-metals gain electrons to get full valence shells. They become negative valence shells. They become negative ions.ions.

Eg) If Cl gains 1 electron it becomes ClEg) If Cl gains 1 electron it becomes Cl1-1-

Cl atom

+++++ - - - - -

++++++ - - - - - -

++++++ - - - - - -

Cl- atom

+++++ - - - - - -

++++++ - - - - - -

++++++ - - - - - -

Chemical BondingChemical Bonding Atoms always bond with each other Atoms always bond with each other

through the valence electrons. through the valence electrons. There are 3 ways in which atoms bond There are 3 ways in which atoms bond

together. We will only study 1 way.together. We will only study 1 way. Ionic bondsIonic bonds

– Occur between metals and non-metalsOccur between metals and non-metals – Metals happily Metals happily transfertransfer their electrons to their electrons to

non-metals which happily accept the non-metals which happily accept the electrons.electrons.

– Electrons transfer making two oppositely Electrons transfer making two oppositely charged IONS which stick togethercharged IONS which stick together

Ionic compounds are formedIonic compounds are formed Ionic compoundsIonic compounds::

– have high melting points. (strong ionic have high melting points. (strong ionic bonds)bonds)

– usually dissolve easily in waterusually dissolve easily in water– are electrolytes – materials that conduct are electrolytes – materials that conduct

electricity when molten or when dissolved electricity when molten or when dissolved (aqueous)(aqueous)

AssignmentAssignment

– AIMS #5AIMS #5– AIMS #6AIMS #6

Writing Chemical Formulas Writing Chemical Formulas – Positive ions balance negative ions to Positive ions balance negative ions to

form neutral compoundsform neutral compoundsE.g. Na + ClE.g. Na + Cl NaCl NaCl

Find the type/charge of ion Find the type/charge of ion formed – From the formed – From the family/groupfamily/group

Na (1+) + Cl (1-)Na (1+) + Cl (1-)

Describe how many ions Describe how many ions are needed to balance the are needed to balance the chargescharges

1Na + 1Cl1Na + 1Cl

Write the compound (metal Write the compound (metal first)first)

NaClNaCl

E.g. Mg + ClE.g. Mg + Cl MgClMgCl22

Find the type/charge of ion Find the type/charge of ion formed – From the formed – From the family/groupfamily/group

Mg (2+) + Cl (1-)Mg (2+) + Cl (1-)

Describe how many ions Describe how many ions are needed to balance the are needed to balance the chargescharges

1Mg + 2Cl1Mg + 2Cl

Write the compound (metal Write the compound (metal first)first) MgClMgCl

22

AssignmentAssignment

– AIMS # 7AIMS # 7– AIMS #8AIMS #8– BLM 8-1, 8-2 (2 pages), 8-3 & 8-4BLM 8-1, 8-2 (2 pages), 8-3 & 8-4

Naming Ionic CompoundsNaming Ionic Compounds Ionic Compounds – electrons are Ionic Compounds – electrons are

transferred from metals to non-metals. transferred from metals to non-metals. The ions stick together. The ions stick together.