Chapter 2 Chemistry Comes Alive: Part A. Matter Anything that has mass and occupies space States of...

Chapter 2 Chapter 2 Chemistry Comes Alive: Part AChemistry Comes Alive: Part A

MatterMatter

Anything that has mass and Anything that has mass and occupies spaceoccupies space

States of matter:States of matter:1.1. Solid—definite shape and volumeSolid—definite shape and volume

2.2. Liquid—definite volume, changeable Liquid—definite volume, changeable shapeshape

3.3. Gas—changeable shape and volumeGas—changeable shape and volume

EnergyEnergyCapacity to do work or put matter into Capacity to do work or put matter into motionmotion

Types of energy:Types of energy:Kinetic—energy in actionKinetic—energy in action

Potential—stored (inactive) energyPotential—stored (inactive) energy

PLAYPLAY Animation: Energy Concepts

Forms of EnergyForms of EnergyChemical energy—stored in bonds of Chemical energy—stored in bonds of chemical substances chemical substances

Electrical energy—results from movement Electrical energy—results from movement of charged particlesof charged particles

Mechanical energy—directly involved in Mechanical energy—directly involved in moving mattermoving matter

Radiant or electromagnetic energy—Radiant or electromagnetic energy—exhibits wavelike properties (i.e., visible exhibits wavelike properties (i.e., visible light, ultraviolet light, and X-rays)light, ultraviolet light, and X-rays)

Energy Form Energy Form ConversionsConversions

Energy may be converted from one form Energy may be converted from one form to anotherto another

Conversion is inefficient because some Conversion is inefficient because some energy is energy is ““lostlost”” as heat as heat

Composition of Composition of MatterMatter

ElementsElementsCannot be broken down by ordinary Cannot be broken down by ordinary chemical means chemical means

Each has unique properties:Each has unique properties:

Physical propertiesPhysical properties

Are detectable with our senses, or Are detectable with our senses, or are measurableare measurable

Chemical propertiesChemical properties

How atoms interact (bond) with How atoms interact (bond) with one anotherone another

Composition of Composition of MatterMatter

AtomsAtomsUnique building blocks for each elementUnique building blocks for each element

Atomic symbol: one- or two-letter Atomic symbol: one- or two-letter chemical shorthand for each elementchemical shorthand for each element

Major Elements of Major Elements of the Human Bodythe Human BodyOxygen (O) Oxygen (O)

Carbon (C) Carbon (C)

Hydrogen (H) Hydrogen (H)

Nitrogen (N)Nitrogen (N)

About 96% of body mass

Lesser Elements Lesser Elements of the Human of the Human

BodyBody About 3.9% of body mass:About 3.9% of body mass:Calcium (Ca), phosphorus (P), potassium Calcium (Ca), phosphorus (P), potassium (K), sulfur (S), sodium (Na), chlorine (Cl), (K), sulfur (S), sodium (Na), chlorine (Cl), magnesium (Mg), iodine (I), and iron (Fe)magnesium (Mg), iodine (I), and iron (Fe)

Trace Elements of Trace Elements of the Human Bodythe Human Body< 0.01% of body mass:< 0.01% of body mass:

Part of enzymes, e.g., chromium (Cr), Part of enzymes, e.g., chromium (Cr), manganese (Mn), and zinc (Zn)manganese (Mn), and zinc (Zn)

Atomic StructureAtomic StructureDetermined by numbers of subatomic Determined by numbers of subatomic particlesparticles

Nucleus consists of neutrons and Nucleus consists of neutrons and protonsprotons

Atomic StructureAtomic StructureNeutronsNeutrons

No chargeNo charge

Mass = 1 atomic mass unit (amu)Mass = 1 atomic mass unit (amu)

ProtonsProtonsPositive chargePositive charge

Mass = 1 amuMass = 1 amu

Atomic StructureAtomic StructureElectronsElectrons

Orbit nucleusOrbit nucleus

Equal in number to protons in atomEqual in number to protons in atom

Negative charge Negative charge

1/2000 the mass of a proton (0 amu)1/2000 the mass of a proton (0 amu)

Models of the Models of the AtomAtom

Orbital model: current model used by Orbital model: current model used by chemistschemists

Depicts probable regions of greatest Depicts probable regions of greatest electron density (an electron cloud)electron density (an electron cloud)

Useful for predicting chemical behavior Useful for predicting chemical behavior of atomsof atoms

Models of the Models of the AtomAtom

Planetary model—oversimplified, Planetary model—oversimplified, outdated modeloutdated model

Incorrectly depicts fixed circular electron Incorrectly depicts fixed circular electron pathspaths

Useful for illustrations (as in the text)Useful for illustrations (as in the text)

Copyright © 2010 Pearson Education, Inc. Figure 2.1

(a) Planetary model (b) Orbital model

Helium atom

2 protons (p+)2 neutrons (n0)2 electrons (e–)

Helium atom

2 protons (p+)2 neutrons (n0)2 electrons (e–)

Nucleus Nucleus

Proton Neutron Electroncloud

Electron

Identifying Identifying ElementsElements

Atoms of different elements contain Atoms of different elements contain different numbers of subatomic different numbers of subatomic particlesparticles

Compare hydrogen, helium and lithium Compare hydrogen, helium and lithium (next slide)(next slide)


Proton

Neutron

Electron

Helium (He)(2p+; 2n0; 2e–)

Lithium (Li)(3p+; 4n0; 3e–)

Hydrogen (H)(1p+; 0n0; 1e–)


Atomic number = number of protons in Atomic number = number of protons in nucleusnucleus


Mass number = mass of the protons and Mass number = mass of the protons and neutronsneutrons

Mass numbers of atoms of an element Mass numbers of atoms of an element are not all identicalare not all identical

Isotopes are structural variations of Isotopes are structural variations of elements that differ in the number of elements that differ in the number of neutrons they containneutrons they contain


Atomic weight = average of mass Atomic weight = average of mass numbers of all isotopesnumbers of all isotopes


Proton

Neutron

Electron

Deuterium (2H)(1p+; 1n0; 1e–)

Tritium (3H)(1p+; 2n0; 1e–)

Hydrogen (1H)(1p+; 0n0; 1e–)

RadioisotopesRadioisotopesSpontaneous decay (radioactivity)Spontaneous decay (radioactivity)

Similar chemistry to stable isotopesSimilar chemistry to stable isotopes

Can be detected with scannersCan be detected with scanners

RadioisotopesRadioisotopesValuable tools for biological research Valuable tools for biological research and medicineand medicine

Cause damage to living tissue:Cause damage to living tissue: Useful against localized cancersUseful against localized cancers

Radon from uranium decay causes lung Radon from uranium decay causes lung cancercancer

Molecules and Molecules and CompoundsCompounds

Most atoms combine chemically with Most atoms combine chemically with other atoms to form molecules and other atoms to form molecules and compoundscompounds

Molecule—two or more atoms bonded Molecule—two or more atoms bonded together (e.g., Htogether (e.g., H22 or C or C66HH1212OO66))

Compound—two or more different kinds Compound—two or more different kinds of atoms bonded together (e.g., Cof atoms bonded together (e.g., C66HH1212OO66))

Mixtures Mixtures Most matter exists as mixturesMost matter exists as mixtures

Two or more components physically Two or more components physically intermixedintermixed

Three types of mixturesThree types of mixturesSolutionsSolutions

ColloidsColloids

SuspensionsSuspensions

Solutions Solutions Homogeneous mixturesHomogeneous mixtures

Usually transparent, e.g., atmospheric Usually transparent, e.g., atmospheric air or seawater air or seawater

SolventSolventPresent in greatest amount, usually a Present in greatest amount, usually a liquidliquid

Solute(s)Solute(s)Present in smaller amountsPresent in smaller amounts

Concentration of Concentration of SolutionsSolutions

Expressed asExpressed asPercent, or parts per 100 partsPercent, or parts per 100 partsMilligrams per deciliter (mg/dl)Milligrams per deciliter (mg/dl)Molarity, or moles per liter (M)Molarity, or moles per liter (M)

1 mole = the atomic weight of an element 1 mole = the atomic weight of an element or molecular weight (sum of atomic or molecular weight (sum of atomic weights) of a compound in gramsweights) of a compound in grams1 mole of any substance contains 6.02 1 mole of any substance contains 6.02 10102323 molecules (Avogadro molecules (Avogadro’’s number)s number)

Colloids and Colloids and SuspensionsSuspensions

Colloids (emulsions)Colloids (emulsions)Heterogeneous translucent mixtures, Heterogeneous translucent mixtures, e.g., cytosole.g., cytosolLarge solute particles that do not settle Large solute particles that do not settle outoutUndergo sol-gel transformationsUndergo sol-gel transformations

Suspensions:Suspensions:Heterogeneous mixtures, e.g., bloodHeterogeneous mixtures, e.g., bloodLarge visible solutes tend to settle outLarge visible solutes tend to settle out


Solution

Soluteparticles

Soluteparticles

Soluteparticles

Solute particles are verytiny, do not settle out or

scatter light.

ColloidSolute particles are larger

than in a solution and scatterlight; do not settle out.

SuspensionSolute particles are very

large, settle out, and mayscatter light.

ExampleMineral water

ExampleGelatin

ExampleBlood

Mixtures vs. Mixtures vs. CompoundsCompounds

MixturesMixturesNo chemical bonding between No chemical bonding between components components Can be separated physically, such as by Can be separated physically, such as by straining or filteringstraining or filteringHeterogeneous or homogeneousHeterogeneous or homogeneous

CompoundsCompoundsCan be separated only by breaking bondsCan be separated only by breaking bondsAll are homogeneousAll are homogeneous

Chemical BondsChemical BondsElectrons occupy up to seven electron Electrons occupy up to seven electron shells (energy levels) around nucleus shells (energy levels) around nucleus

Octet rule: Except for the first shell Octet rule: Except for the first shell which is full with two electrons, atoms which is full with two electrons, atoms interact in a manner to have eight interact in a manner to have eight electrons in their outermost energy electrons in their outermost energy level (valence shell)level (valence shell)

Chemically Inert Chemically Inert ElementsElements

Stable and unreactiveStable and unreactive

Outermost energy level fully occupied Outermost energy level fully occupied or contains eight electronsor contains eight electrons

Copyright © 2010 Pearson Education, Inc. Figure 2.5a

Helium (He)(2p+; 2n0; 2e–)

Neon (Ne)(10p+; 10n0; 10e–)

2e 2e8e

(a) Chemically inert elements

Outermost energy level (valence shell) complete

Chemically Chemically Reactive Reactive ElementsElementsOutermost energy level not fully Outermost energy level not fully

occupied by electronsoccupied by electrons

Tend to gain, lose, or share electrons Tend to gain, lose, or share electrons (form bonds) with other atoms to (form bonds) with other atoms to achieve stability achieve stability

Copyright © 2010 Pearson Education, Inc. Figure 2.5b

2e4e

2e8e

1e

(b) Chemically reactive elementsOutermost energy level (valence shell) incomplete

Hydrogen (H)(1p+; 0n0; 1e–)

Carbon (C)(6p+; 6n0; 6e–)

1e

Oxygen (O)(8p+; 8n0; 8e–) Sodium (Na)

(11p+; 12n0; 11e–)

2e6e

Types of Chemical Types of Chemical BondsBonds

Ionic Ionic

Covalent Covalent

HydrogenHydrogen

Ionic BondsIonic BondsIons are formed by transfer of valence Ions are formed by transfer of valence shell electrons between atomsshell electrons between atoms

Anions (– charge) have gained one or Anions (– charge) have gained one or more electronsmore electrons

Cations (+ charge) have lost one or more Cations (+ charge) have lost one or more electronselectrons

Attraction of opposite charges results in Attraction of opposite charges results in an ionic bondan ionic bond

Copyright © 2010 Pearson Education, Inc. Figure 2.6a-b

Sodium atom (Na)(11p+; 12n0; 11e–)

Chlorine atom (Cl)(17p+; 18n0; 17e–)

Sodium ion (Na+) Chloride ion (Cl–)

Sodium chloride (NaCl)

+ –

(a) Sodium gains stability by losing one electron, and chlorine becomes stable by gaining one electron.

(b) After electron transfer, the oppositely charged ions formed attract each other.

Formation of an Formation of an Ionic BondIonic Bond

Ionic compounds form crystals instead Ionic compounds form crystals instead of individual moleculesof individual molecules

NaCl (sodium chloride)NaCl (sodium chloride)

Copyright © 2010 Pearson Education, Inc. Figure 2.6c

CI–

Na+

(c) Large numbers of Na+ and Cl– ions associate to form salt (NaCl) crystals.

Covalent BondsCovalent BondsFormed by sharing of two or more Formed by sharing of two or more valence shell electrons valence shell electrons

Allows each atom to fill its valence shell Allows each atom to fill its valence shell at least part of the timeat least part of the time


+

Hydrogenatoms

Carbonatom

Molecule ofmethane gas (CH4)

Structuralformulashows singlebonds.

(a) Formation of four single covalent bonds: carbon shares four electron pairs with four hydrogen atoms.

or

Resulting moleculesReacting atoms


or

Oxygenatom

Oxygenatom

Molecule ofoxygen gas (O2)

Structuralformulashowsdouble bond.(b) Formation of a double covalent bond: Two

oxygen atoms share two electron pairs.


+


+ or

Nitrogenatom

Nitrogenatom

Molecule ofnitrogen gas (N2)

Structuralformulashowstriple bond.(c) Formation of a triple covalent bond: Two

nitrogen atoms share three electron pairs.


Covalent BondsCovalent BondsSharing of electrons may be equal or Sharing of electrons may be equal or unequalunequal

Equal sharing produces electrically Equal sharing produces electrically balanced nonpolar moleculesbalanced nonpolar molecules• COCO22

Covalent BondsCovalent Bonds• Unequal sharing by atoms with different Unequal sharing by atoms with different

electron-attracting abilities produces electron-attracting abilities produces polar moleculespolar molecules– HH22OO

• Atoms with six or seven valence shell Atoms with six or seven valence shell electrons are electronegative, e.g., oxygenelectrons are electronegative, e.g., oxygen

• Atoms with one or two valence shell Atoms with one or two valence shell electrons are electropositive, e.g., sodiumelectrons are electropositive, e.g., sodium

Hydrogen BondsHydrogen Bonds• Attractive force between electropositive Attractive force between electropositive

hydrogen of one molecule and an hydrogen of one molecule and an electronegative atom of another electronegative atom of another moleculemolecule– Common between dipoles such as waterCommon between dipoles such as water– Also act as intramolecular bonds, holding Also act as intramolecular bonds, holding

a large molecule in a three-dimensional a large molecule in a three-dimensional shapeshape

PLAYPLAY Animation: Hydrogen Bonds

Copyright © 2010 Pearson Education, Inc.

(a) The slightly positive ends (+) of the watermolecules become aligned with the slightlynegative ends (–) of other water molecules.

+

–

–

–– –

+

+

+

+

+

Hydrogen bond(indicated bydotted line)

Figure 2.10a


(b) A water strider can walk on a pond because of the highsurface tension of water, a result of the combinedstrength of its hydrogen bonds.

Chemical Chemical ReactionsReactions

• Occur when chemical bonds are formed, Occur when chemical bonds are formed, rearranged, or brokenrearranged, or broken

• Represented as chemical equationsRepresented as chemical equations

• Chemical equations contain:Chemical equations contain:– Molecular formula for each reactant and Molecular formula for each reactant and

product product – Relative amounts of reactants and Relative amounts of reactants and

products, which should balance products, which should balance

Examples of Examples of Chemical Chemical EquationsEquationsH + H H + H H H22 (hydrogen gas) (hydrogen gas)

4H + C 4H + C CH CH44 (methane) (methane)

(reactants) (product)

Patterns of Patterns of Chemical Chemical ReactionsReactions• Synthesis (combination) reactionsSynthesis (combination) reactions

• Decomposition reactionsDecomposition reactions

• Exchange reactionsExchange reactions

Synthesis Synthesis ReactionsReactions

• A + B A + B AB AB– Always involve bond formationAlways involve bond formation– AnabolicAnabolic


ExampleAmino acids are joined together toform a protein molecule.

(a) Synthesis reactions

Smaller particles are bondedtogether to form larger,

more complex molecules.

Amino acidmolecules

Proteinmolecule

Decomposition Decomposition ReactionsReactions

• AB AB A + B A + B– Reverse synthesis reactionsReverse synthesis reactions– Involve breaking of bondsInvolve breaking of bonds– Catabolic Catabolic


ExampleGlycogen is broken down to releaseglucose units.

Bonds are broken in largermolecules, resulting in smaller,

less complex molecules.

(b) Decomposition reactions

Glucosemolecules

Glycogen

Exchange Exchange ReactionsReactions

• AB + C AB + C AC + B AC + B– Also called displacement reactionsAlso called displacement reactions– Bonds are both made and brokenBonds are both made and broken


ExampleATP transfers its terminal phosphategroup to glucose to form glucose-phosphate.

Bonds are both made and broken(also called displacement reactions).

(c) Exchange reactions

Glucose Adenosine triphosphate (ATP)

Adenosine diphosphate (ADP)Glucosephosphate

+

+

Oxidation-Oxidation-Reduction Reduction

(Redox) Reactions(Redox) Reactions• Decomposition reactions: Reactions in Decomposition reactions: Reactions in which fuel is broken down for energywhich fuel is broken down for energy

• Also called exchange reactions because Also called exchange reactions because electrons are exchanged or shared electrons are exchanged or shared differentlydifferently– Electron donors lose electrons and are Electron donors lose electrons and are

oxidizedoxidized– Electron acceptors receive electrons and Electron acceptors receive electrons and

become reducedbecome reduced

Chemical Chemical ReactionsReactions

• All chemical reactions are either All chemical reactions are either exergonic or endergonicexergonic or endergonic– Exergonic reactions—release energyExergonic reactions—release energy

• Catabolic reactionsCatabolic reactions

– Endergonic reactions—products contain Endergonic reactions—products contain more potential energy than did reactantsmore potential energy than did reactants• Anabolic reactionsAnabolic reactions

Chemical Chemical ReactionsReactions• All chemical reactions are theoretically All chemical reactions are theoretically

reversiblereversible– A + B A + B AB AB– AB AB A + B A + B

• Chemical equilibrium occurs if neither a Chemical equilibrium occurs if neither a forward nor reverse reaction is forward nor reverse reaction is dominantdominant

• Many biological reactions are Many biological reactions are essentially irreversible due toessentially irreversible due to– Energy requirementsEnergy requirements– Removal of productsRemoval of products

Rate of Chemical Rate of Chemical ReactionsReactions

• Rate of reaction is influenced by:Rate of reaction is influenced by: temperature temperature rate rate particle size particle size rate rate concentration of reactant concentration of reactant rate rate

• Catalysts: Catalysts: rate without being rate without being chemically changedchemically changed– Enzymes are biological catalystsEnzymes are biological catalysts

Chapter 2 Chemistry Comes Alive: Part A. Matter Anything that has mass and occupies space States of...

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