..

CHAPTER 2: CHEMISTRYCHAPTER 2: CHEMISTRY

Composition of MatterComposition of Matter2-12-1

MatterMatter

EVERYTHING IS MADE OF MATTEREVERYTHING IS MADE OF MATTER MatterMatter: anything that occupies space : anything that occupies space

and has massand has mass MassMass: quantity of matter an object : quantity of matter an object

hashas Mass is NOT the same as weightMass is NOT the same as weight

WeightWeight: the pull of gravity on an object: the pull of gravity on an object

ElementsElements

Pure substances that cannot be broken Pure substances that cannot be broken down chemically into simpler kinds of down chemically into simpler kinds of mattermatter

About 100 elementsAbout 100 elements Only 30 crucial to living thingsOnly 30 crucial to living things Almost 90% mass of all living things made Almost 90% mass of all living things made

from combinations of only 4 elements!from combinations of only 4 elements! Oxygen (O)Oxygen (O) Carbon (C) Carbon (C) Hydrogen (H)Hydrogen (H) Nitrogen (N)Nitrogen (N)

What we areWhat we aremade of…..made of…..

ElementsElements Each element has chemical symbolsEach element has chemical symbols

Consists of 1 or 2 lettersConsists of 1 or 2 letters Most cases symbol derives from first Most cases symbol derives from first

letters in name of elementletters in name of element Some come from Latin words for Some come from Latin words for

elementselements Example: Symbol for sodium = Na from Example: Symbol for sodium = Na from

word word natriumnatrium (Latin) (Latin)

Atomic Mass

Element Name

Atomic Number

Element Symbol

AtomsAtoms

Simplest particle of an element that Simplest particle of an element that has all the properties of that elementhas all the properties of that element

So small cannot be observedSo small cannot be observed Scientists therefore make models Scientists therefore make models

describing the structure/properties of describing the structure/properties of atomsatoms

Two main parts:Two main parts: NucleusNucleus Electron shellElectron shell

NucleusNucleus

Central core of atomCentral core of atom Made up of two particles:Made up of two particles:

PROTONSPROTONSNEUTRONSNEUTRONS

Positively chargedPositively charged NeutralNeutral

++ 00

ElectronsElectrons High-energy particles with little mass.High-energy particles with little mass. Move around nucleus at very high Move around nucleus at very high

speedspeed Move within different Move within different energy levelsenergy levels Electrons in outermost energy levels Electrons in outermost energy levels

have the have the mostmost energy energy Each energy level can hold a certain Each energy level can hold a certain

number of electronsnumber of electrons First energy level holds 2 First energy level holds 2 Second energy level holds 8Second energy level holds 8

Electron orbits: Example Electron orbits: Example CarbonCarbon

CompoundsCompounds

Pure substance made up of atoms of two or Pure substance made up of atoms of two or more elementsmore elements

The amount of atoms in the compound are fixedThe amount of atoms in the compound are fixed Example: Water, HExample: Water, H22O indicates that atoms always O indicates that atoms always

combine in a proportion of two hydrogen atoms to combine in a proportion of two hydrogen atoms to one oxygen atomone oxygen atom

Physical and chemical properties of a compound Physical and chemical properties of a compound differ from the physical and chemical properties differ from the physical and chemical properties of individual elements that compose itof individual elements that compose it

How do elements form How do elements form compounds?compounds?

Most atoms are not stable as individual Most atoms are not stable as individual atomsatoms

Depends on the number and arrangement Depends on the number and arrangement of electrons in the atoms of elementsof electrons in the atoms of elements Atoms are stable when the outermost energy Atoms are stable when the outermost energy

level is filledlevel is filled Most atoms are not stable in their natural state Most atoms are not stable in their natural state

therefore tend to react with other atoms therefore tend to react with other atoms in ways that make the atoms more stable in ways that make the atoms more stable (atoms react to make themselves more stable)(atoms react to make themselves more stable)

These reactions = chemical reactionsThese reactions = chemical reactions

Chemical ReactionsChemical ReactionsWhat does a chemical reaction consist of?What does a chemical reaction consist of? chemical bonds are brokenchemical bonds are broken Atoms are rearrangedAtoms are rearranged New chemical bonds—attachments—are New chemical bonds—attachments—are

formedformed

Chemical Vs. Physical Chemical Vs. Physical ChangeChange

This is only a change in the state of the matter:

Solid liquid; Solid gas

Gas solid; Gas liquid

Liquid solid; Liquid gas

This is a change in the composition of matter

Ionic BondsIonic Bonds

Forms when atoms Forms when atoms gain or losegain or lose electronselectrons

Why do atoms form bonds? TO BECOME MORE STABLE

-Has 7e-

-Wants 8e-

-Has 3e-

-Wants 2e-

Covalent BondsCovalent Bonds

Forms when two atoms Forms when two atoms shareshare one or one or more electronsmore electrons

-Hydrogen has 1e- in the outer electron shell

-oxygen has 6e- in the outer electron shell

-hydrogen wants 2e-

-oxygen wants 8e-

-they share to make each other happy

Why do atoms form bonds? TO BECOME MORE STABLE

Ionic or Covalent Bond?Ionic or Covalent Bond?

MetalsMetals NonmetalsNonmetals Ionic: metal + nonmetalIonic: metal + nonmetal

Ex. NaClEx. NaCl Covalent: nonmetal + nonmetalCovalent: nonmetal + nonmetal

Ex. HClEx. HCl

Review QuestionsReview Questions Define element, atom, compound, molecule.Define element, atom, compound, molecule. How are particles arranged in the atom?How are particles arranged in the atom? How can we predict which elements are How can we predict which elements are

stable under natural conditions and which stable under natural conditions and which elements tend to undergo chemical elements tend to undergo chemical reactions?reactions?

How does an ionic bond differ from a covalent How does an ionic bond differ from a covalent bond?bond?

Neon seldom, if ever, combines with other Neon seldom, if ever, combines with other elements to form compounds. Why is this so?elements to form compounds. Why is this so?

In the early 1900’s, hydrogen gas was used to In the early 1900’s, hydrogen gas was used to inflate airships. After one large airship inflate airships. After one large airship crashed and caught on fire, helium gas began crashed and caught on fire, helium gas began to be used to inflate airships. Why was helium to be used to inflate airships. Why was helium preferred over hydrogen?preferred over hydrogen?

Review Questions: Review Questions: AnswersAnswers

Define element, atom, compound, molecule. Define element, atom, compound, molecule. ElementsElements are substances that cannot be broken are substances that cannot be broken down chemically into simpler chemical substances. down chemically into simpler chemical substances. An An atom atom is the simplest part of an element that is the simplest part of an element that retains all of the properties of the element. A retains all of the properties of the element. A compoundcompound is a pure substance made up of two or is a pure substance made up of two or more elements. A more elements. A moleculemolecule is the simplest part of is the simplest part of a substance that retains all of the properties of the a substance that retains all of the properties of the substance and that can exist in a free state.substance and that can exist in a free state.

How are particles arranged in the atom? How are particles arranged in the atom? ProtonsProtons and and neutrons neutrons make up the nucleus of the atom. make up the nucleus of the atom. ElectronsElectrons move around the nucleus move around the nucleus

Review Questions: Review Questions: AnswersAnswers How can we predict which elements are stable How can we predict which elements are stable

under natural conditions and which elements tend under natural conditions and which elements tend to undergo chemical reactions? to undergo chemical reactions? Stable elements Stable elements have filled outermost energy levels. Elements with have filled outermost energy levels. Elements with unfilled outmost energy levels tend to be reactiveunfilled outmost energy levels tend to be reactive

How does an ionic bond differ from a covalent How does an ionic bond differ from a covalent bond? bond? In an ionic bond, ions with opposite electrical In an ionic bond, ions with opposite electrical charges attract each other. In a covalent bond, the charges attract each other. In a covalent bond, the atoms share pairs of electronsatoms share pairs of electrons

Neon seldom, if ever, combines with other elements Neon seldom, if ever, combines with other elements to form compounds. Why is this so? to form compounds. Why is this so? Neon has the Neon has the maximum number of electrons that its outermost maximum number of electrons that its outermost energy levels can hold. Thus, neon is stable and energy levels can hold. Thus, neon is stable and tends not to react with other atoms. tends not to react with other atoms.

In the early 1900’s, hydrogen gas was used to In the early 1900’s, hydrogen gas was used to inflate airships. After one large airship crashed and inflate airships. After one large airship crashed and caught on fire, helium gas began to be used to caught on fire, helium gas began to be used to inflate airships. Why was helium preferred over inflate airships. Why was helium preferred over hydrogen? hydrogen? Hydrogen is very reactive, while helium Hydrogen is very reactive, while helium is relatively unreactive.is relatively unreactive.

ENERGYENERGY

Ch. 2-2Ch. 2-2

Energy & MatterEnergy & Matter

The ability to do work or cause change.The ability to do work or cause change. Energy cannot be destroyed or createdEnergy cannot be destroyed or created Energy can be converted into another Energy can be converted into another

formform Ex. Light bulb: electrical energy Ex. Light bulb: electrical energy radiant radiant

energy (light) energy (light) thermal energy (heat) thermal energy (heat)

States of MatterStates of Matter

All atoms & molecules in any All atoms & molecules in any substance are in constant motionsubstance are in constant motion

Rate which atoms or molecules move Rate which atoms or molecules move determines the state it is in:determines the state it is in: SolidSolid Liquid Liquid GasGas

States of MatterStates of Matter

SolidSolid Definite shapeDefinite shape Definite volumeDefinite volume Not compressible Not compressible Tightly packed particlesTightly packed particles

LiquidLiquid Indefinite shapeIndefinite shape Definite volumeDefinite volume Not compressibleNot compressible Medium packed particlesMedium packed particles

GasGas Indefinite shapeIndefinite shape Indefinite volumeIndefinite volume CompressibleCompressible Loosely packed particlesLoosely packed particles

Liquid

Solid

Gas

Chemical ReactionsChemical Reactions

Living things undergo thousands of Living things undergo thousands of chem. Rxns during lifetimechem. Rxns during lifetime

Consist of:Consist of: ReactantsReactants: left side of equation: left side of equation ProductsProducts: right side of equation: right side of equation

COCO22 + H + H22O O H H22COCO33

REACTANTS PRODUCTS

Energy TransferEnergy Transfer1. We take in food 1. We take in food 2. Sugars undergo series of chemical rxns2. Sugars undergo series of chemical rxns3. Sugar & substances are broken down to 3. Sugar & substances are broken down to

carbon dioxide & water (cellular carbon dioxide & water (cellular respiration)respiration)

4. During this process, energy is released 4. During this process, energy is released for use by bodyfor use by body

Exergonic ReactionsExergonic Reactions: release of energy: release of energy Endergonic ReactionsEndergonic Reactions: absorption of : absorption of

energyenergy

Activation EnergyActivation Energy

In order for exergonic & endergonic In order for exergonic & endergonic reactions to begin, energy must be added reactions to begin, energy must be added to the reactantsto the reactants

The amount of energy needed to start a The amount of energy needed to start a chemical reaction = chemical reaction = activation energyactivation energy

CatalystsCatalysts reduce the amount of activation reduce the amount of activation energy needed to begin a reactionenergy needed to begin a reaction EnzymesEnzymes: crucial catalyst for living things: crucial catalyst for living things

We have thousands, each made for specific reactionsWe have thousands, each made for specific reactions

Activation Energy DiagramActivation Energy Diagram

Reduction-Oxidation Reduction-Oxidation ReactionsReactions

Many chemical rxns that help transfer Many chemical rxns that help transfer energyenergy in living things involve the transfer in living things involve the transfer of of electronselectrons These known as reduction-oxidation rxns OR These known as reduction-oxidation rxns OR

redox rxnsredox rxns Oxidation rxnsOxidation rxns: reactant loses one or more : reactant loses one or more

electronselectrons becoming more positively charged becoming more positively charged Reduction rxnsReduction rxns: reactants gain one or more : reactants gain one or more

electronselectrons becoming more negatively charged becoming more negatively charged Always occur togetherAlways occur together OILRIGOILRIG: : OOxidation xidation IIs s LLoss oss RReduction eduction IIs s GGain (of ain (of

electrons)electrons)

Example: Redox ReactionExample: Redox Reaction

Formation of NaCl: Sodium ChlorideFormation of NaCl: Sodium Chloride Sodium atom loses electron to Sodium atom loses electron to

achieve stability when it forms ionic achieve stability when it forms ionic bond bond sodium atom undergoes sodium atom undergoes oxidationoxidation

When a chlorine atom gains an When a chlorine atom gains an electron electron undergoes reduction undergoes reduction

Na + Cl Na + Cl NaCl NaCl

Review QuestionsReview Questions

What are the three states of matter?What are the three states of matter? How can a substance be changed from a liquid to How can a substance be changed from a liquid to

a gas?a gas? State the difference between endergonic and State the difference between endergonic and

exergonic reactionsexergonic reactions Explain how a catalyst affects a reactionExplain how a catalyst affects a reaction Why does a reduction reaction always accompany Why does a reduction reaction always accompany

an oxidation reactionan oxidation reaction Living things need a constant supply of energy, Living things need a constant supply of energy,

even though many of the chemical reactions they even though many of the chemical reactions they undergo release energy. Why is this true?undergo release energy. Why is this true?

Review Questions: Review Questions: AnswersAnswers What are the three states of matter? What are the three states of matter? Matter can exist as a Matter can exist as a

solid, liquid or gassolid, liquid or gas How can a substance be changed from a liquid to a gas? How can a substance be changed from a liquid to a gas? A A

substance can be changed from a liquid into a gas by substance can be changed from a liquid into a gas by heatingheating

State the difference between endergonic and exergonic State the difference between endergonic and exergonic reactions: reactions: Endergonic reactions involve a net absorption of Endergonic reactions involve a net absorption of free energy. Exergonic reactions involve a net release of free energy. Exergonic reactions involve a net release of free energy.free energy.

Explain how a catalyst affects a reaction: Explain how a catalyst affects a reaction: A catalyst lowers A catalyst lowers the amount of activation energy that is required for a the amount of activation energy that is required for a chemical reaction to begin.chemical reaction to begin.

Why does a reduction reaction always accompany an Why does a reduction reaction always accompany an oxidation reaction? oxidation reaction? If an atom is oxidized (loses electrons), If an atom is oxidized (loses electrons), then another atom must be reduced (accept those electrons then another atom must be reduced (accept those electrons that have been lost).that have been lost).

Living things need a constant supply of energy, even though Living things need a constant supply of energy, even though many of the chemical reactions they undergo release many of the chemical reactions they undergo release energy. Why is this true? energy. Why is this true? Even exergonic reactions need a Even exergonic reactions need a small amount of energy—activation energy—to begin. small amount of energy—activation energy—to begin.

SOLUTIONSSOLUTIONS

Ch. 2-3Ch. 2-3

Describing SolutionsDescribing Solutions

Mixture which one or more substances are uniformly Mixture which one or more substances are uniformly distributed in another substance.distributed in another substance. SoluteSolute: substance dissolved in the solution: substance dissolved in the solution SolventSolvent: substance in which the solute is dissolved: substance in which the solute is dissolved

EXAMPLE: sugar waterEXAMPLE: sugar water Sugar = soluteSugar = solute Water = solventWater = solvent

ConcentrationConcentration of solution is measurement of the of solution is measurement of the amount of solute dissolved in fixed amount of solutionamount of solute dissolved in fixed amount of solution The more solute dissolved, the greater the concentration of The more solute dissolved, the greater the concentration of

solutionsolution Aqueous Aqueous solutions: water is solventsolutions: water is solvent

Crucial for living thingsCrucial for living things

MixtureMixture

Two main kinds:Two main kinds: HomogeneousHomogeneous: uniformly mixed : uniformly mixed

throughoutthroughout Ex. Sugar waterEx. Sugar water

HeterogeneousHeterogeneous: not uniformly mixed : not uniformly mixed throughoutthroughout

Ex. Oil & vinegar salad dressingEx. Oil & vinegar salad dressing

Acids & BasesAcids & Bases

One of the most important aspects of a One of the most important aspects of a living system is the degree of its living system is the degree of its

acidity or alkalinity acidity or alkalinity Alkaline = BaseAlkaline = Base

AcidsAcids

If the number of If the number of hydroniumhydronium (H (H33OO++) ions in ) ions in solution is solution is greatergreater than the number of than the number of hydroxide hydroxide (OH(OH--) ions in solution = ) ions in solution = acidacid Ex. of Acidic solutions: Orange juice, VinegarEx. of Acidic solutions: Orange juice, Vinegar Ex. of common acid: hydrochloric acid (HCl) Ex. of common acid: hydrochloric acid (HCl) How does it affect our everyday lives? How does it affect our everyday lives?

Sulfur dioxide (SOSulfur dioxide (SO22): produced by burning fossil fuels, ): produced by burning fossil fuels, reacts with water in the atmosphere to produce acid reacts with water in the atmosphere to produce acid rainrain

Acid rain: can make lakes too acidic to support lifeAcid rain: can make lakes too acidic to support life

BasesBases

If the number of If the number of hydroxidehydroxide (OH (OH--) ions in ) ions in solution is solution is greatergreater than the number of than the number of hydroniumhydronium (H (H33OO++) ions in solution = ) ions in solution = basicbasic Ex. of common basic solutions:Ex. of common basic solutions:

Cleaning agentsCleaning agents Soaps Soaps

Ex. of common base: sodium hydroxide Ex. of common base: sodium hydroxide (NaOH)(NaOH)

NeutralNeutral

If the number of hydronium ions If the number of hydronium ions equals the number of hydroxide ions equals the number of hydroxide ions in solutionin solution Example: Pure waterExample: Pure water

**Hydronium ion = H**Hydronium ion = H33OO++

**Hydroxide ion = OH**Hydroxide ion = OH--

pH ScalepH Scale

Scale for comparing the relative Scale for comparing the relative concentrations of hydronium ions and concentrations of hydronium ions and hydroxide ions in a solutionhydroxide ions in a solution

pH of 0-7 = AcidicpH of 0-7 = Acidic pH of 0 is VERY acidicpH of 0 is VERY acidic

pH of 8-14 = BasicpH of 8-14 = Basic pH of 14 is VERY basicpH of 14 is VERY basic

pH of 7 = NeutralpH of 7 = Neutral pH of solution is measured with pH of solution is measured with Litmus PaperLitmus Paper

pH ScalepH Scale

A solution with a pH of 3 compared to a A solution with a pH of 3 compared to a solution with a pH of 5solution with a pH of 5 pH of 3 is 100X more acidic than pH of 5pH of 3 is 100X more acidic than pH of 5 pH of 3 is 10X more acidic than pH of 4pH of 3 is 10X more acidic than pH of 4 pH of 1 is 1000X more acidic than pH of 4pH of 1 is 1000X more acidic than pH of 4 pH of 13 is 10X more basic than pH of 12pH of 13 is 10X more basic than pH of 12

**there is a 10X difference between each **there is a 10X difference between each number in the pH scalenumber in the pH scale

What does the pH scale look What does the pH scale look like?like?

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

ACID BASE

NEUTRAL

BuffersBuffers

Chemical substances that neutralize Chemical substances that neutralize small amounts of either an acid or small amounts of either an acid or base added to a solutionbase added to a solution

We have complex buffering systems We have complex buffering systems keeping our body fluids at safe levelskeeping our body fluids at safe levels Ex. Stomach acid & urine are acidicEx. Stomach acid & urine are acidic Ex. Intestinal fluid & blood are basicEx. Intestinal fluid & blood are basic

Review QuestionsReview Questions

What is a solution?What is a solution? Describe the dissociation of water.Describe the dissociation of water. What pH value is neutral?What pH value is neutral? Define acid and base.Define acid and base. What is a buffer?What is a buffer? The active ingredient in aspirin is The active ingredient in aspirin is

acetylsalicylic acid. Why would doctors acetylsalicylic acid. Why would doctors recommend buffered aspirin for some recommend buffered aspirin for some people, especially those who have a people, especially those who have a “sensitive” stomach?“sensitive” stomach?

Review Questions: Review Questions: AnswersAnswers

What is a solution? What is a solution? A solution is a mixture in which one or more A solution is a mixture in which one or more substances are uniformly distributed in another substancesubstances are uniformly distributed in another substance

Describe the dissociation of water: Describe the dissociation of water: The oxygen atom of one The oxygen atom of one water molecule removes the hydrogen atom of another water water molecule removes the hydrogen atom of another water molecule. This results in one hydronium ion (Hmolecule. This results in one hydronium ion (H33OO++) and one ) and one hydroxide ion (OHhydroxide ion (OH--))

What pH value is neutral? What pH value is neutral? A pH value of 7 is neutralA pH value of 7 is neutral.. Define acid and base: Define acid and base: An acid is a solution that contains more An acid is a solution that contains more

hydronium ions than hydroxide ions. A base contains more hydronium ions than hydroxide ions. A base contains more hydroxide ions than hydronium ions. hydroxide ions than hydronium ions.

What is a buffer? What is a buffer? A buffer is a chemical substance that A buffer is a chemical substance that neutralizes small amounts of acids or bases added to a solution.neutralizes small amounts of acids or bases added to a solution.

The active ingredient in aspirin is acetylsalicylic acid. Why The active ingredient in aspirin is acetylsalicylic acid. Why would doctors recommend buffered aspirin for some people, would doctors recommend buffered aspirin for some people, especially those who have a “sensitive” stomach? especially those who have a “sensitive” stomach? The buffer The buffer reduces the acidity of the aspirin and thus is less irritating to the reduces the acidity of the aspirin and thus is less irritating to the stomach. stomach.