Chemistry I Honors

Chapter 1“Chemistry and You”

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Welcome to Welcome to the World of the World of Chemistry!!Chemistry!!

Why study Chemistry?• Explain the natural world

– Why?• Prepare for a career

– Directly- in a lab– Indirectly- problem solving and thinking

skills• Be an informed citizen

– Vote– Don’t get scammed

The Nature of MatterThe Nature of MatterThe Nature of MatterThe Nature of MatterChemists are interested in the nature of matter and Chemists are interested in the nature of matter and

how this is related to its atoms and molecules.how this is related to its atoms and molecules.

GoldGoldMercuryMercury

Chemistry & MatterChemistry & Matter

• We can explore the We can explore the MACROSCOPIC MACROSCOPIC world — what we can see — world — what we can see —

• to understand the to understand the NanoscaleNanoscale worlds worlds we cannot see.we cannot see.

• We write We write SYMBOLSSYMBOLS to describe to describe these worlds.these worlds.

A Chemist’s View of WaterA Chemist’s View of Water

H2O (gas, liquid, solid)

MacroscopicMacroscopicMacroscopicMacroscopic

SymbolicSymbolicSymbolicSymbolicNanoscaleNanoscaleNanoscaleNanoscale

A Chemist’s ViewA Chemist’s View

2 H2(g) + O2 (g) --> 2 H2O(g)

MacroscopicMacroscopicMacroscopicMacroscopic

SymbolicSymbolicSymbolicSymbolicNanoscaleNanoscaleNanoscaleNanoscale

So What is Chemistry?

• The study of matter, its composition, properties, and the changes it undergoes.

• Pure science gathers knowledge for knowledge’s sake

• Applied science uses chemistry to attain certain goals, in fields like medicine, agriculture, and manufacturing (Technology)

Branches of Chemistry• Analytical Chemistry -studies composition of

substances.• Organic Chemistry -compounds containing

carbon• Inorganic Chemistry -substances without

carbon• Biochemistry- Chemistry of living things• Physical Chemistry studies behavior of

substances– rates and mechanisms of reactions– energy transfers

Scientific Method - orderly way to Scientific Method - orderly way to solve solve

problemsproblems1.1. State the problem. State the problem. 2.2. Gather information. (Research)Gather information. (Research)3.3. Form a Form a hypothesishypothesis..

(educated guess)(educated guess)4.4. Test the hypothesis. Test the hypothesis.

(Experiment & make observations)(Experiment & make observations)

5.5. Analyze the data. Analyze the data. 6.6. Form a conclusion.Form a conclusion.

(Hypothesis was correct, incorrect, or inconclusive)(Hypothesis was correct, incorrect, or inconclusive)

7. 7. Communicate the results. Communicate the results. (Publish)(Publish)

Observation –Observation – Something you sense or a Something you sense or a

measurement you make. measurement you make. FACTS!!!FACTS!!!

(Do this during experiment)(Do this during experiment)

Value Judgment – Value Judgment – fact + opinionfact + opinion

((Do this before/during Conclusion)Do this before/during Conclusion)

Don’t make decisions during a Don’t make decisions during a lab!lab!Record the facts, just the facts!Record the facts, just the facts!

Do you know the Do you know the difference between the difference between the independent and independent and dependent variables?dependent variables?

Independent Variable

The independent, or manipulated variable, is a factor that is intentionally varied by the experimenter.

(Placed on X (horizontal) axis of graph)

Ex. John is going to use 25g., 50g., 100g., 250g., 500g. of sugar in his experiment.

(the mass of sugar john decided to use eachtrial would be the independent variable!)

Dependent Variable

The dependent, or responding variable, is the factor that may change as a result of changes made in the independent variable.

(Placed on Y (vertical) axis of graph)

Independent Independent VariableVariable

Dependent Dependent VariableVariable

TitleTitle

Where did it all begin?

The word “atom” comes from the

Greek word “atomos” which means

indivisible.

The idea that all matter is made up of

atoms was first proposed by the

Greek philosopher Democritus in the 5th

century B.C.

EmpedoclesEmpedocles (Greek, born in Sicily, 490 B.C.)

Suggested there were only four basic elements – earth, air, fire, – earth, air, fire,

and waterand water. The elementary substances (atoms to us)

combined in various ways to make everything.

No experiments to support ideaIdea of ‘atomos’

Atomos = ‘indivisible’‘Atom’ is derived

The Hellenic Market

Fire Water Earth Air

~~

Alchemy

• True ancestor of chemistry

Goals: • Changing cheap metals into gold• Find the “Elixir of Life” a universal cure

for disease, and a way of prolonging life.

• Alchemists were not successful, however…

The AlchemistFrankly, I’d be

satisfied if I could turn gold

into lead!

Important Contributions

• a) lab techniques & tools– Distillation – separates the parts of a

solution – based on differences in boiling point temperatures

• b) alloys – solutions of metals– brass, bronze, solder, pewter, sterling

silver, etc.

During the Renaissance PeriodDuring the Renaissance Period(15(15thth – 16 – 16thth centuries) alchemy centuries) alchemy made the change to “Chemistry”!made the change to “Chemistry”!They began to question the old They began to question the old beliefs, but it wasn’t until the beliefs, but it wasn’t until the 1770’s that the first experiments 1770’s that the first experiments were done to disprove were done to disprove Empedocles’ idea of “Four Basic Empedocles’ idea of “Four Basic Principles”Principles”

What is Matter?• Matter is anything that has mass

and takes up space.

• Mass is the amount of matter an object contains.

Is Air matter?

What are the two criteria for matter?

Does it take up space?Does it have mass?

All matter has the property of inertiaAll matter has the property of inertia

Inertia is the resistance of matter to Inertia is the resistance of matter to a change of direction or rate ofa change of direction or rate ofmotion.motion.

What is NOT Matter?•Energy!

• All matter is affected by energyAll matter is affected by energy

Energy is the ability to do work or cause change.Potential Energy – stored (in bonds between atoms or by position)Kinetic Energy – doing work or causing change

Activation Energy is often needed to change potential energy to kinetic energy.

Types of Energies• Mechanical

• Chemical (stored in chemical bonds)

• Heat (thermal)

• Nuclear

• Light (radiant)

• Electrical

• Sound

•All chemical reactions involve energy

changes

•energy is either absorbed or liberated!.

EnergyEnergy can change can change forms!forms!

Conservation of EnergyConservation of Energy

• Energy can be neither created or Energy can be neither created or destroyed in ordinary changes (not destroyed in ordinary changes (not nuclear), it can only change form. nuclear), it can only change form.

• Its not just a good idea, its the Its not just a good idea, its the lawlaw..

MATTER

Can it be physically separated?

Homogeneous Homogeneous MixtureMixture

(solution)(solution)

Heterogeneous Heterogeneous MixtureMixture Compound Element

MIXTUREMIXTURE PURE SUBSTANCE

yes no

Can it be chemically decomposed?

noyesIs the composition uniform?

noyes

ColloidsColloids SuspensionsSuspensions

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Matter Flowchart

A substance has a definite, unvarying composition –

it contains only one type of contains only one type of mattermatter

- either an element or a - either an element or a compoundcompound

water, ammonia, sucrose, gold, oxygen

ELEMENTS• ElementsElements - pure substances that - pure substances that

cannot be decomposed by ordinary cannot be decomposed by ordinary means into other substances.means into other substances.

Sodium Bromine

Aluminum

Only one kind of atomOnly one kind of atom

118 elements have been identified

• 82 elements occur naturally on Earth

gold, aluminum, lead, oxygen, carbon

• 36 elements have been created by scientists

technetium, americium, seaborgium 1.4

Elements have a 1 or two letter Elements have a 1 or two letter symbolsymbol, , and compounds have a and compounds have a formulaformula..An element’s first letter always capitalized; An element’s first letter always capitalized; if there is a second letter, it is written if there is a second letter, it is written lowercaselowercase: B, Ba, C, Ca, H, He: B, Ba, C, Ca, H, He

Copper Copper atoms on atoms on silica silica surface.surface.

• An An atomatom is the smallest particle of is the smallest particle of an element that has the chemical an element that has the chemical properties of the element.properties of the element.

Distance across = 1.8 nanometer (1.8 x 10-9 m)

Compounds• Composed of 2 or

more elements chemically combined in a fixed ratio

• Properties differ from those of individual elements– EX: table salt (NaCl)

ammonia (NH3)glucose (C6H12O6)

More than oneMore than one kind of atom!kind of atom!

Sodium metal

• Soft, can be cut with a knife

• Shiny• Good

conductor of electricity

• Very reactive

Sodium in water

Chlorine gas

• Greenish gas

• Poisonous

• Heavier than air

Sodium in chlorine gas

Sodium chloride, NaCl

• Sodium chloride dissolves in water rather than reacts with water.

• Sodium chloride is a white solid, not a poisonous green gas.

• Sodium chloride is its own substance with its own properties, not those of either sodium or chlorine.

CHEMICAL COMPOUNDSCHEMICAL COMPOUNDS are are composed of atoms and composed of atoms and can can only be decomposed by chemical only be decomposed by chemical meansmeans..

Mixtures

• Blend of 2 or more substances- does NOT involve reaction or change in composition of either substance.

• Variable composition

• Homogeneous or Heterogeneous

1. Homogenous mixture –

composition completely uniform completely uniform throughoutthroughout

1.4

(No lumps, bumps, chunks, or layers)(No lumps, bumps, chunks, or layers)

Only 1 phaseOnly 1 phase

Also called Solutions

Phase- any part of a system withPhase- any part of a system with uniform composition and propertiesuniform composition and properties

Heterogeneous mixture – composition is not uniform throughout.

visibly separate phases (2 or more)

Physical means can be used to separate a mixture into its pure components.

magnet

1.4

distillationFiltrationFiltrationDecantingDecantingCrystallizationCrystallizationChromatographyChromatography

Separation of a Mixture

Distillation: takes advantage of different boiling points.

NaCl boils at 1415 NaCl boils at 1415 ooCCWater boils at 100Water boils at 100 ooC

Filtration separates a liquid from a solid.

Compound vs. Mixture

Compound Mixture

Made of one kindof material

Made of more thanone kind of material

Made by a chemical change

Made by a physical change

Definitecomposition

Variablecomposition

Properties of Properties of MatterMatter• Physical properties

• - can be determined without changing the identity of the substance

Physical properties

can be either extensive or intensive

An extensive property

depends upon the amount of matter present.

• mass

• length

• volume

1.6

An intensive property of a material does not depend upon how much matter is present.

• density physical state

• temperature malleability

• color ductility

• solubility melting point

• conductivity boiling point

STATES OF MATTERSTATES OF MATTERSTATES OF MATTERSTATES OF MATTER•SolidsSolids — have rigid shape, fixed — have rigid shape, fixed

volume. Incompressiblevolume. Incompressible

•LiquidsLiquids — definite volume;— definite volume;

• take shape of container; flow; take shape of container; flow; incompressible.incompressible.

•GasesGases — — No definite shape or volume No definite shape or volume - expand to fill their container; - expand to fill their container; compressible; flowcompressible; flow

States of MatterStates of Matter

Solid

Liquid

Gas

Definite Volume?

YES

YES

NO

Definite Shape?

YES

NO

NO

Result of a TemperatureIncrease?

Small Expans.

Small Expans.

Large Expans.

Will it Compress?

NO

NO

YES

• Chemical properties describe the way a substance can change or react to form other substances. These properties, then, must be determined using a process that changes the identity of the substance of interest. •In other words, we have to define chemical properties of a substance by the chemical changes it undergoes.

•Does it burn?

•Explode?

•React in water?

•iron plus oxygen forms rust,iron plus oxygen forms rust,

so the ability to rust is a so the ability to rust is a

chemical property of ironchemical property of iron

Physical vs. Chemical

• Examples:

– melting point

– flammable

– density

– magnetic

– tarnishes in air

physical

chemical

physical

physical

chemical

CHANGES

A physical change

does not alter the composition or identity of a substance.

1.6

ExEx.: Crushing.: Crushing Cutting Cutting Phase changesPhase changes

DissolvingDissolving MixingMixing

A chemical change - a change in which one or more substances are converted into different substances.

Alters the composition or identity of the substance(s) involved.

• Signs of chemical change:– Fizzing/bubbling– Smoke– Fire/Explosion– Energy given off (heat, light, sound)– Precipitate formed (insoluble solid)– Color change– Odor change

http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA0/MOVIES/S1047.MOV

A Colorful Demonstration: The Remsen Reaction

Physical vs. Chemical

• Examples:

– rusting iron

– dissolving in water

– burning a log

– melting ice

– grinding spices

ChemicalChemical

PhysicalPhysicalChemicalChemical

PhysicalPhysicalPhysicalPhysical

Law of conservation of mass• Matter cannot be created nor

destroyed in any chemical reaction.

• During any chemical reaction, the mass of the products is always equal to the mass of the reactants.

• All the mass can be accounted for:– Burning of wood results in products that

appear to have less mass as ashes; where is the rest?

- Page 55

reactants = product

43.43 g Original mass = 43.43 g Final mass

Classification of Matter