chapter 1 “ introduction to chemistry”

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Chapter 1“Introduction to

Chemistry”

Chapter 2“Matter & Change”

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What is Chemistry? Chemistry is the study of the

composition of “matter” – (matter is anything with mass and occupies space), its composition, properties, and the changes it undergoes.

Has a definite affect on everyday life - taste of foods, grades of gasoline, etc.

Living and nonliving things are made of matter.

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Chemistry is the study of the composition, structure, and properties of matter and the changes it undergoes – such as burning fuels.

C2H5OH + 3 O2 2 CO2 + 3 H2O + Energy Reactants Products

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5 Major Areas of Chemistry1) Analytical Chemistry- concerned with

the composition of substances.2) Inorganic Chemistry- primarily deals

with substances without carbon3) Organic Chemistry- essentially all

substances containing carbon4) Biochemistry- Chemistry of living things5) Physical Chemistry- describes the

behavior of chemicals (ex. stretching); involves lots of math!

Boundaries not firm – they overlap and interact

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What is Chemistry? Pure chemistry- gathers knowledge for

the sake of knowledge Applied Chemistry- is using chemistry

to attain certain goals, in fields like medicine, agriculture, and manufacturing – leads to an application

* Aspirin (C9H8O4) - to relieve pain* Use of TECHNOLOGY (benefit!)

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Why Study Chemistry? Everyone and everything around us

involves chemistry – explains our world What in the world isn’t Chemistry? Helps you make choices; helps make

you a better informed citizen A possible career for your future Used to attain a specific goal

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Why Study Chemistry?• Major component of acid rain• May cause burns• Has been found in tumors• Used in nuclear plants• Used in the distribution of

pesticides• Used in animal research

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Chemistry Far and WideChemists design materials to fit

specific needs – velcro (Patented in 1955) perfume, steel, ceramics, plastics,

rubber, paints, nonstick cooking utensils, polyester fibers

Two different ways to look at the world: macroscopic and microscopic

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Chemistry Far and WideEnergy – we constantly have

greater demands–We can conserve it; use wisely–We can try to produce more; oil

from soybeans to make biodiesel–fossil fuels, solar, batteries (that

store energy – rechargeable?), nuclear (don’t forget pollution!)

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Chemistry Far and WideMedicine and Biotechnology-

–Supply materials doctors use to treat patients

–vitamin C, penicillin, aspirin (C9H8O4)

–materials for artery transplants and hipbones

–bacteria producing insulin

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Chemistry Far and WideAgriculture

–Produce the world’s food supply–Use chemistry for better

productivity – soil, water, weeds–plant growth hormones–ways to protect crops; insecticides–disease resistant plants

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Chemistry Far and Wide The Environment

–both risks and benefits involved in discoveries

–Pollutants need to be 1) identified and 2) prevented

–Lead paint was prohibited in 1978; Leaded gasoline? Drinking water?

–carbon dioxide, ozone, global warming

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Chemistry Far and WideThe Universe

–Need to gather data from afar, and analyze matter brought back to Earth

–composition of the planets–analyze moon rocks (or Mars)–planet atmospheres–life on other planets?

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Alchemy – developed the tools and techniques for working with chemicals

The word chemistry comes from alchemy – practiced in China and India since 400 B.C.

Alchemy has two sides:–Practical: techniques for working

with metals, glass, dyes, etc.–Mystical: concepts like perfection –

gold was a perfect metal

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An Experimental ApproachIn the 1500s, a shift started from

alchemy to science – King Charles II was a supporter of the sciences

“Royal Society of London for the Promotion of Natural Knowledge”

Encouraged scientists to use more experimental evidence, and not philosophical debates

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LavoisierIn the late 1700s, Antoine

Lavoisier helped transform chemistry from a science of observation to the science of measurement – still used today

He settled a long-standing debate about burning, which was…–Oxygen was required!

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The Scientific MethodA logical approach to solving

problems or answering questions.Starts with observation- noting and

recording information and factshypothesis- a proposed

explanation for the observation; must be tested by an experiment

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Steps in the Scientific Method1. Observations (uses your senses)

a) quantitative involves numbers = 95oF

b) qualitative is word description = hot

2. Formulating hypotheses (ideas)- possible explanation for the

observation, or “educated” guess

3. Performing experiments (the test)- gathers new information to help

decide whether the hypothesis is valid

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Scientific Method “controlled” experiment- designed to

test the hypothesis only two possible answers:

1) hypothesis is right (supported)2) hypothesis is wrong (not supported)

We gather data and observations by doing the experiment

Modify hypothesis - repeat the cycle

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Scientific Method We deal with variables, or factors that can

change. Two types:1) Manipulated variable (or independent

variable) is the one that we change2) Responding variable (or dependent

variable) is the one observed during the experiment

For results to be accepted, the experiment needs to always produce the same result

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Outcomes over the long term… Theory (Model)

- A set of well-tested hypotheses that give an overall explanation of some natural phenomenon – not able to be proved

Natural Law (or Scientific Law)- The same observation applies to many different systems; summarizes results

- an example would be: the Law of Conservation of Mass

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Law vs. Theory

A law summarizes what has happened.

A theory (model) is an attempt to explain why it happened – this changes as new information is gathered.

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Collaboration / Communication When scientists share ideas by

collaboration and communication, they increase the likelihood of a successful outcome

Collaboration How is communication done? Is the Internet reliable information?

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Luis Alvarez Story

• Iridium (30 – 130 times) normal• It’s very rare???• This layer is found around the planet

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Luis Alvarez Story

???

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Luis Alvarez Story

X

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Problem Solving in Chemistry We are faced with problems each day,

and not just in chemistry A solution (answer) needs to be found Trial and Error may work sometimes? But, there is a method to problem

solving that works better, and these are skills that no one is born knowing – they need to be learned.

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Problem Solving in Chemistry Effective problem solving usually

involves two general steps:1) Developing a plan2) Implementing that plan

The skills you use to solve a word problem in chemistry are NOT different from those techniques used in shopping, cooking, or planning a party.

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Solving Numeric Problems Measurements are an important part

of chemistry; thus many of our word problems involve use of mathmatics–Word problems are real life

problems, and sometimes more information is presented than needed for a solution

Following skills presented will help you become more successful

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Solving Numeric Problems The three steps we will use for

solving a numeric word problem are:

1) Analyze2) Calculate3) Evaluate

The following slides tell the meaning of these three steps in detail.

Let’s learn how to ACE these numeric word problems!

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Solving Numeric Problems1) Analyze: this is the starting point

– Determine what are the known factors, and write them down on your paper!

– Determine what is the unknown. If it is a number, determine the units needed

– Plan how to relate these factors- choose an equation; use table or graph

This is the heart of successful problem solving techniques – it is the PLAN

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Solving Numeric Problems2) Calculate: perform the mathematics

– If your plan is correct, this is the easiest step.

– Calculator used? Do it correctly!– May involve rearranging an

equation algebraically; or, doing some conversion of units to some other units.

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Solving Numeric Problems3) Evaluate: – the finishing step

– Is it reasonable? Make sense? Do an estimate for the answer, and check your calculations.

– Need to round off the answer?– Do you need scientific notation?– Do you have the correct units?– Did you answer the question?

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Solving Conceptual Problems Not all word problems in chemistry

involve doing calculations Nonnumeric problems are called

conceptual problems – ask you to apply concepts to a new situation

Steps are:1) Analyze and 2) Solve

Plan needed to link known to unknown, but no checking units or calculations

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MatterMatter is anything that: a) has

mass, and b) takes up spaceMass = a measure of the amount

of “stuff” (or material) the object contains (don’t confuse this with weight, a measure of gravity)

Volume = a measure of the space occupied by the object

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Describing Matter Properties used to describe matter

can be classified as:1) Extensive – depends on the

amount of matter in the sample- Mass, volume, calories are examples

2) Intensive – depends on the type of matter, not the amount present

- Hardness, Density, Boiling Point

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Properties are… Words that describe matter (adjectives) Physical Properties- a property that can

be observed and measured without changing the material’s composition.

Examples- color, hardness, m.p., b.p. Chemical Properties- a property that

can only be observed by changing the composition of the material.

Examples- ability to burn, decompose, ferment, react with, etc.

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States of matter1) Solid- matter that can not flow (definite

shape) and has definite volume.2) Liquid- definite volume but takes the

shape of its container (flows).3) Gas- a substance without definite volume

or shape and can flow.– Vapor- a substance that is currently a

gas, but normally is a liquid or solid at room temperature. (Which is correct: “water gas”, or “water vapor”?)

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States 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

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4th state: Plasma - formed at high temperatures; ionized

phase of matter as found in the sun

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Three Main Phases

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Solid Liquid Gas

Melt Evaporate

CondenseFreeze

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Copper Phases - Solid

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Copper Phases - Liquid

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Copper Phases – Vapor (gas)

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Physical vs. Chemical Change Physical change will change the visible

appearance, without changing the composition of the material.–Boil, melt, cut, bend, split, crack– Is boiled water still water?

Can be reversible, or irreversible Chemical change - a change where a

new form of matter is formed.–Rust, burn, decompose, ferment

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Mixtures are a physical blend of at least two substances; have variable composition. They can be either:

1) Heterogeneous – the mixture is not uniform in composition• Chocolate chip cookie, gravel, soil.

2) Homogeneous - same composition throughout; called “solutions”• Kool-aid, air, salt water

Every part keeps it’s own properties.

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Solutions are homogeneous mixtures Mixed molecule by molecule, thus too

small to see the different parts Can occur between any state of

matter: gas in gas; liquid in gas; gas in liquid; solid in liquid; solid in solid (alloys), etc.

Thus, based on the distribution of their components, mixtures are called homogeneous or heterogeneous.

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Phase? The term “phase” is used to describe

any part of a sample with uniform composition of properties.

A homogeneous mixture consists of a single phase

A heterogeneous mixture consists of two or more phases.

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Separating MixturesSome can be separated easily by

physical means: rocks and marbles, iron filings and sulfur (use magnet)

Differences in physical properties can be used to separate mixtures.

Filtration - separates a solid from the liquid in a heterogeneous mixture (by size) – Figure 2.7, page 46

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Separation of a MixtureComponents of dyes such as ink may be separated by paper chromatography.

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Separation of a MixtureDistillation: takes advantage of different boiling points.

NaCl boils at 1415 oC

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Substances are either:a) elements, orb) compounds

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Substances: element or compound Elements- simplest kind of matter

– cannot be broken down any simpler and still have properties of that element!

– all one kind of atom. Compounds are substances that can be

broken down only by chemical methods– when broken down, the pieces have

completely different properties than the original compound.

– made of two or more atoms, chemically combined (not just a physical blend!)

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Compound vs. MixtureCompound 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

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Which is it?

ElementCompoundMixture

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Elements vs. CompoundsCompounds can be broken down

into simpler substances by chemical means, but elements cannot.

A “chemical change” is a change that produces matter with a different composition than the original matter.

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Chemical ChangeA change in which one or more substances are converted into different substances.

Heat and light are often evidence of a chemical change.

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Properties of Compounds Quite different properties than their

component elements. Due to a CHEMICAL CHANGE, the

resulting compound has new and different properties:• Table sugar – carbon, hydrogen,

oxygen• Sodium chloride – sodium, chlorine• Water – hydrogen, oxygen

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Classification of Matter

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Symbols & Formulas Currently, there are ”117” elements Elements have a 1 or two letter symbol,

and compounds have a formula. An element’s first letter always capitalized;

if there is a second letter, it is written lowercase: B, Ba, C, Ca, H, He

You Must Learn the elements names and symbols

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Chemical Changes The ability of a substance to undergo

a specific chemical change is called a chemical property.• iron plus oxygen forms rust, so the

ability to rust is a chemical property of iron

During a chemical change (also called chemical reaction), the composition of matter always changes.

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Chemical Reactions are… When one or more substances are

changed into new substances. Reactants- the stuff you start with Products- what you make The products will have NEW

PROPERTIES different from the reactants you started with

Arrow points from the reactants to the new products

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Recognizing Chemical Changes1) Energy is absorbed or released

(temperature changes hotter or colder)2) Color changes (watch out for dilution)3) Gas production (bubbling, fizzing, or odor

change; smoke)4) formation of a precipitate - a solid that

separates from solution (won’t dissolve)

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Conservation of Mass 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?

Law of conservation of mass

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- Page 55

reactants = product

43.43 g Original mass = 43.43 g Final mass