What is Chemistry ?

Chapter 1

What is Chemistry?

• The study of the matter, 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.

5 Major Areas of Chemistry

1) Analytical Chemistry- concerned with the composition of substances.

2) Inorganic Chemistry- primarily deals with substances without carbon

3) Organic Chemistry- essentially all substances containing carbon

5 Major Areas of Chemistry

4) Biochemistry- Chemistry of living things

5) 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–Nylon, Aspirin (C9H8O4), Technology

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

• Used to attain a specific goal

Why Study Chemistry?

• Give examples in your daily life that involve use of chemistry, and things that do not?

What is matter ?

• Matter is anything that: –Has mass

–takes up space

• What about heat?

What is matter ?

• Mass = 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

Types of Matter

• Substance- a particular kind of matter – pure

• Mixture- more than one kind of matter

Pure Substances

Pure Substances are either:

a) elements, or

b) compounds

Pure Substance

• Elements- simplest kind of matter

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

– all one kind of atom.

Symbols & Formulas

• Currently, there are 118 elements

– 94 occur naturally

• Elements have a 1 or two letter symbol, and compounds have a formula.

• An element’s first letter is always capitalized; if there is a second letter, it is written lowercase: B, Ba, C, Ca, H, He

• Some names come from Latin or other languages

Pure Substance• 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!)

Types of Matter

• 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

1) Example: Chocolate chip cookie, gravel, soil.

Types of Matter

1) Homogeneous - same composition throughout; called “solutions”

• Examples: Kool-aid, air, salt water

• Every part keeps it’s own properties.

Types of Matter

• 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.

Separating Mixtures• Some 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 solid substances from liquids and solutions.

Separation of a Mixture

Components of dyes such as ink may be separated by paper chromatography.

Separation of a Mixture

Distillation: takes advantage of different boiling points.

NaCl boils at 1415 oC

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

Physical vs. Chemical Properties

• Words that describe matter (adjectives)

– Physical Properties- a property that can be observed and measured without changing the material’s composition.

• Examples- ?

Physical vs. Chemical Properties

• Chemical Properties- a property that can only be observed by changing the composition of the material.

– Examples- ?

Physical vs. Chemical Property

• Examples:– melting point

– flammable

– density

– magnetic

– tarnishes in air

Changes in Matter

Chemical and Physical Changes

Physical vs. Chemical Change• Physical change will change the visible appearance,

without changing the composition of the material.

– Can be reversible, or irreversible

– Examples?

• Chemical change - a change where a new form of matter is formed.

– Examples?

Physical and Chemical Changes

Chemical Changes Physical Changes

Rusting Nail Melting Ice

Bleaching a Stain Boiling Water

Burning a Log Sawing a log in half

Tarnishing Silver Tearing Paper

Fermenting of Grapes Breaking a Glass

Souring of Milk Pouring of Milk

Digesting food Phase Changes

MATTERCan it be physically

separated?

Can it be chemically decomposed?

CompoundElement

PURE SUBSTANCE

no

no yes

Homogeneous Mixture

(solution)

Heterogeneous Mixture

MIXTURE

yes

Is the composition uniform?

noyes

Matter

Substances and Mixtures• Examples:– Graphite (all C atoms)

– Diamond (a form of carbon)

– sugar (sucrose)

– paint

– gasoline

– Sulfur

– Rust

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.

4th state: Plasma - formed at high temperatures; ionized phase of matter as found in the sun

Products manufacturedusing plasmas impact our daily lives:

•Computer chips and integrated circuits •Computer hard drives •Electronics •Machine tools •Medical implants and prosthetics •Audio and video tapes •Aircraft and automobile engine parts

•Printing on plastic food containers •Energy-efficient window coatings •High-efficiency window coatings •Safe drinking water •Voice and data communications components •Anti-scratch and anti-glare coatings on eyeglasses and other optics

freezing

melting or fusion

condensation

evaporation

sublimation

deposition

SOLID LIQUID GAS

Phase Changes

The Scientific Method• A logical approach to solving problems or

answering questions.

• Starts with observation- noting and recording information and facts

• hypothesis- a proposed explanation for the observation; must be tested by an experiment

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

a) quantitative involves numbers = 95oFb) 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

Scientific Method• “controlled” experiment- designed to test the hypothesis

• only two possible answers:1) hypothesis is right2) hypothesis is wrong

• We gather data and observations by doing the experiment

• Modify hypothesis - repeat the cycle

Scientific Method• We deal with variables, or factors that can change.

Two types:

1) Manipulated variable (or independent variable) is the one that we change

2) 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

Scientific Method• 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

Law vs. TheoryA 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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Using your senses to obtain information

Hypothesis is a proposed explanation; should be based on previous knowledge; an “educated” guess

The procedure that is used to test the hypothesis

A well-tested explanation for the observations; cannot be proven due to new discoveries

Tells what happened