Physical and Chemical Properties

1
Physical and Chemical Properties
Examples of Physical Properties
Boiling point Color Slipperiness Electrical
conductivity Melting point Taste Odor Dissol
ves in water Shininess (luster)
Softness Ductility Viscosity (resistance to
flow) Volatility Hardness Malleability Densit
y (mass / volume ratio)
Examples of Chemical Properties
Burns in air Reacts with certain
acids Decomposes when heated Explodes
Reacts with certain metals Reacts with certain
nonmetals Tarnishes Reacts with water Is
toxic
Chemical properties ONLY be observed during
chemical reactions
2
Changes in Matter

• Changes that alter the state or appearance of the
  matter without altering the composition are
  called physical changes.
• Changes that alter the composition of the matter
  are called chemical changes.
• During the chemical change, the atoms that are
  present rearrange into new molecules, but all of
  the original atoms are still present.

3
Evidence a Chemical Change

• Indications of a Chemical Reaction
• Evolution of heat, light, and/or sound
• Production of a gas
• Formation of a precipitate
• Color change

4
What Is Matter?

• Matter is defined as anything that occupies space
  and has mass.
• Even though it appears to be smooth and
  continuous, matter is actually composed of a lot
  of tiny little pieces we call atoms and molecules.

5
Atoms and Molecules

• Atoms are the tiny particles that make up all
  matter.
• In most substances, the atoms are joined together
  in units called molecules.
• The atoms are joined in specific geometric
  arrangements.

6
Some Properties of Solids, Liquids, and Gases
Property Solid Liquid
Gas
Shape Has definite shape Takes the shape
of Takes the shape the container
of its container Volume Has a definite
volume Has a definite volume Fills the volume
of the container Arrangement
of Fixed, very close Random, close
Random, far apart Particles Interactions between
Very strong Strong Essentially
none particles
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MATTER
yes
no
Can it be physically separated?
MIXTURE
PURE SUBSTANCE
no
yes
no
yes
Can it be chemically decomposed?
Is the composition uniform?
Homogeneous Mixture (solution)
Heterogeneous Mixture
Compound
Element
Colloids
Suspensions
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8
Pure Substances

• Element (on Periodic Table)
• identical atoms which cannot be broken down
  further and still maintain identity
• EX copper wire, aluminum foil

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9
Pure Substances

• Compound
• composed of 2 or more elements in a fixed ratio
• properties differ from those of individual
  elements
• EX table salt (NaCl)

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10
Pure Substances

• 1. Law of Definite Composition
• A given compound always contains the same, fixed
  ratio of elements (water is always one atom of
  oxygen and two atoms of hydrogen).
• 2. Law of Multiple Proportions
• Elements can combine in different whole number
  ratios to form different compounds (H2O vs. H2O2).

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11
Mixtures

• Variable combination of 2 or more pure
  substances.

Heterogeneous (not uniform)
Homogeneous (uniform)
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12
Mixtures

• Solution
• homogeneous mixture
• very small particles (lt 1 nm)
• which are evenly distributed
• no Tyndall effect

• particles dont settle
• EX rubbing alcohol

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13
Mixtures

• Colloid
• heterogeneous mixture
• medium-sized particles (between
• 1 nm and 1000 nm)
• Tyndall effect (scatter light)
• particles dont settle
• EX milk, butter, fog

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ationsarts/pages/chem
14
Mixtures

• Suspension
• Heterogeneous mixture
• large particles (gt 1000 nm)
• Tyndall effect
• particles settle out
• EX freshly-squeezed juices, Italian salad
  dressing

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15
Elements, Compounds, and Mixtures
oxygen atoms
hydrogen atoms
hydrogen atoms
(b) a compound (water)
(c) a mixture (hydrogen and oxygen)
(d) a mixture (hydrogen and oxygen)
(a) an element (hydrogen)
Dorin, Demmin, Gabel, Chemistry The Study of
Matter , 3rd Edition, 1990, page 68
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Gold, An Alloy
Gold
Copper
Silver
24 karat gold 18 karat gold 14
karat gold
18/24 atoms Au
24/24 atoms Au
14/24 atoms Au
17
Separating Mixtures

• Magnet
• Filter
• Decant
• Evaporation
• Centrifuge
• Chromatography
• Distillation
• ALL PHYSICAL CHANGES!!

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Centrifugation

• Spin sample very rapidly denser materials go to
  bottom (outside)
• Separate blood into serum and plasma
• Serum (clear)
• Plasma (contains red blood cells RBCs)
• Check for anemia (lack of iron)

AFTER
Before
Blood
Serum
RBCs
A B C
19
Law of Conservation of Mass
Reactants yield Products
20
PracticeClassify Each Change as Physical or
Chemical

• Evaporation of rubbing alcohol.
• Sugar turning black when heated.
• An egg splitting open and spilling out.
• Sugar fermenting.
• Bubbles escaping from soda.
• Bubbles that form when hydrogen peroxide is mixed
  with blood.

21
PracticeClassify Each Change as Physical or
Chemical, Continued

• Evaporation of rubbing alcohol physical.
• Sugar turning black when heated chemical.
• An egg splitting open and spilling out
  physical.
• Sugar fermenting chemical.
• Bubbles escaping from soda physical.
• Bubbles that form when hydrogen peroxide is mixed
  with blood chemical.