Download PP_7_Classifying_matter___physical_and_chemical_changes

Matter
Matter, does it matter?
Yes…it does!
Chemistry is the study of matter
and the changes it undergoes.
Matter
We define matter by using
two criteria.
Something is considered to
be matter if it:



Has mass
Takes up space
What are some
examples?
Matter
Not Matter
Energy
Light
Ideas
Happiness
Love
Classifying matter - Why?
1.
2.
3.
To organize what we have
When things are organized – we know what
we have
And more importantly, we know what we do
NOT have.
Classifying matter
Matter
Does it have a fixed formula?
Yes
Substance
*Having a fixed formula
*Cannot be separated by
physical means
No
Mixture
*No fixed formula
*Can be separated
by physical means
Classifying matter
Substances
Can it be separated chemically?
No
Yes
Element
*Simplest form of matter
*Cannot be broken down further
*Found on the periodic table
Compound
*Two or more elements
* Can be broken down
H2O
-> H2
+
O2
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!)
Symbols & Formulas
 Currently, there are 117 elements -Only 92
of the 115 presently known elements occur
naturally.


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
Some elements pair up and only exist as
diatomic molecules
Hydrogen, Nitrogen, Fluorine, Oxygen, Iodine, Chlorine,
and Bromine are always found as diatomic molecules:
How do I remember this? H N F O I Cl Br
•HONClFIBr (say HONKLE-fibber)
•BrINClHOF (say Brinckle-hoff)
•I Have No Bright Or Clever Friends
•ClIF H Bron
•HOFBrINCl Twins (twins because they exist in pairs)
•There are seven such elements. The first one is the first
element Hydrogen; the rest form a 7 on the periodic table:
N, O, F across, then going down Cl, Br, I.
Elements vs. Compounds
 Compounds 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.
What does this drawing
represent?
Is this a compound, element,
or both?
What does this drawing
represent?
Is this compound,
or element?
Answer: Element
What does this drawing
represent?
Is this a compound,
element, or both?
What does this drawing
represent?
Is this a compound,
or element?
Answer: compound
What does this drawing
represent?
Is this a compound, element
or both?
What does this drawing
represent?
Is this a compound,
or element or mixture of
both?
Answer: both compounds
and elements
Identify each of the containers as containing either
elements, compounds, or both
Unnumbered Figure, pg. 9
Investigating Chemistry, 2nd Edition
© 2009 W.H. Freeman & Company
Identify each of the containers as containing either
elements, compounds, or both
Unnumbered Figure, pg. 9
Investigating Chemistry, 2nd Edition
© 2009 W.H. Freeman & Company
Answers:
Elements: b
Compounds: a, d, e
Both compounds and elements: c
Classifying matter
Mixtures
Is every sample taken the same?
No
Yes
Heterogeneous
*Every sample is different
*Usually easy to separate
Homogenous
*Every sample is the same
* Called “Solution”
Solute
What gets dissolved
Solvent
Usually water
Mixtures

Have variable composition.
Homogeneous Mixture

Having visibly indistinguishable parts; solution.
Heterogeneous Mixture

Having visibly distinguishable parts.
Copyright © Cengage Learning.
All rights reserved
Homogeneous Mixtures
Copyright © Cengage Learning.
All rights reserved
Homogeneous vs.
Heterogeneous Mixtures
Copyright © Cengage Learning.
All rights reserved
Classification of Matter
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
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.
Some Examples of
Physical and Chemical Properties
Physical Properties
Chemical Properties
Temperature
Amount
Color
Odor
Melting point
Solubility
Electrical conductivity
Hardness
Rusting (of iron)
Combustion (of coal)
Tarnishing (of silver)
Hardening (of cement)
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

States Of Matter
Solids:
.
States Of Matter
Liquids:

Indefinite shape, definite
volume

Take the shape of
container

Particles are close
together, but mobile

Particles move slowly
States Of Matter
Gases:

Indefinite shape

Indefinite volume

Take the shape and volume of container

Particles are far apart

Particles move fast
States Of Matter
Plasma: Energized gases

Do not have a fixed volume.
They are mostly empty
space and can be
compressed.

Do not have a fixed shape.
They tend to fill the entire
container.
States Of Matter
How do we change states of matter?
It requires energy.
What does the energy do?
It makes the molecules move. This causes
friction, which results in heat being generated
4th state: Plasma - formed at
high temperatures; ionized phase
of matter as found in the sun
Condense
Freeze
Evaporate
Melt
Solid
Liquid
Gas
Learning Check S1
Match: (1) solid, (2) liquid, or (3) gas.
____ A. Has a definite volume, but shape
of the container.
____ B. Its particles are moving rapidly.
____ C. Fills the volume of a container.
____ D. Particles are in a fixed structure.
____ E. Particles are close together, but mobile.
38
Solution S1
Match: (1) solid, (2) liquid, or (3) gas.
_2_ A. Has a definite volume, but shape of the
container.
_3_ B. Its particles are moving rapidly.
_3_ C. Fills the volume of a container.
_1_ D. Particles are in a fixed structure.
_2_ E. Particles are close together, but mobile.
39
Physical vs Chemical
Properties
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.
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

Physical and
Chemical
Changes
How to tell the
difference
Physical Change

Change in the form of a substance, not in its
chemical composition.


Example: boiling or freezing water
Can be used to separate a mixture into pure
compounds, but it will not break compounds
into elements.



Distillation
Filtration
Chromatography
Copyright © Cengage Learning.
All rights reserved
Physical Change
Substance
may
seem different, but
the way the atoms
link up is the same.
It’s a physical change if
It
changes shape or
size
It dissolves
It
changes phase
(freezes, boils,
evaporates,
Chemical Change
Changes the way
the molecules link
up
Makes new
substances
It’s a chemical change if….
It
burns
 Temperature
changes without
heating/cooling
It’s a chemical change if...
 It
bubbles
(makes a
gas)
It’s a chemical change if...
 It
changes
color
 It
forms a
precipitate
What kind of change is it if
someone...
 Tears
up paper?
Physical change
 Mixes salt and water?
Physical change
What kind of change is it if
someone...
 Burns
paper?
Chemical change
 Evaporates salt
water?
Physical change
What kind of change is it if
someone...
Mixes
vinegar and
baking soda?
Chemical change
Chemical Change
A change in which one or more
substances are converted into different
substances.
Heat and
light are
often
evidence of
a chemical
change.
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.

Recognizing Chemical Changes
1) Energy is absorbed or released
(temperature changes hotter or colder)
2) Color changes
3) Gas production (bubbling, fizzing, or odor
change; smoke)
4) formation of a precipitate - a solid that
separates from solution (won’t dissolve)
5) Irreversibility - not easily reversed
But, there are examples of these that are not
chemical – boiling water bubbles, etc.
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