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
- Page 8
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
Matter
MATTER
no
Can it be physically
separated?
PURE SUBSTANCE
no
Can it be chemically
decomposed?
Element
yes
MIXTURE
yes
Compound
yes
Is the composition
uniform?
Homogeneous
Mixture
(solution)
no
Heterogeneous
Mixture
Substances and Mixtures
• Examples:
– Graphite (all C atoms)
– Diamond (a form of carbon)
– sugar (sucrose)
– paint
– gasoline
– Sulfur
– Rust
States of matter
1) 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 manufactured
using plasmas impact our daily lives:
•Computer chips and integrated circuits
•Printing on plastic food containers
•Computer hard drives
•Energy-efficient window coatings
•Electronics
•High-efficiency window coatings
•Machine tools
•Safe drinking water
•Medical implants and prosthetics
•Voice and data communications components
•Audio and video tapes
•Anti-scratch and anti-glare coatings on
eyeglasses and other optics
•Aircraft and automobile engine parts
Phase Changes
sublimation
deposition
freezing
SOLID
LIQUID
melting or
fusion
evaporation
condensation
GAS
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 Method
1. 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
Scientific Method
•
•
“controlled” experiment- designed to test the
hypothesis
only two possible answers:
1) hypothesis is right
2) 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. 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.
- Page 22
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
Tells what happened
A well-tested explanation for the
observations; cannot be proven due to new
discoveries