Transcript Ionic and Molecular Compounds

Ionic and Molecular Compounds
Classifying Compounds
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There are about 109 elements but they
can be combined to make millions of
compounds.
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Elements are commonly classified as
METALS and NONMETALS, therefore
compounds are formed three
combinations:
1.
metals-nonmetals: ionic compounds
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2.
nonmetal-nonmetal: molecular
compounds
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3.
NaCl
SO3
metal-metal: inter-molecular
compounds
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Brass (CuZn) an alloy
Method for Classification
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The properties of compounds can be used to
classify compounds as ionic or molecular.
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Diagnostic Tests- a lab procedure conducted
to identify or classify chemicals.
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Important states of matter in chemical
formulas: solid (s), liquid (l), gas (g), and
aqueous (aq).
Investigation 3.1
Empirical Definitions of Compounds
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Based on you experience, what properties
might be used to classify compounds as ionic
or molecular?
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Why is a control conductivity test on tap
water?
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Disposal – all chemical waste can be disposed
down the drain with lots of water.
Evidence Table
Chemical
 Formula
 Class (I or m)
 State (s, l, g)
 Solubility (yes/no)
 Solution color
 Electrical conductivity (yes/no)
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Evidence Table – Inv. 3.1
Chemical
formula
Class
State
Solubility Solution
Color
Electrical
Conductiv
Analysis
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Empirical definitions – what properties
are true for ionic and molecular
Evaluation
What is judged to be adequate: design,
procedure, and skills?
 Are you confident in your results?
 Where your prediction correct?
 What can you do to improve your
confidence in these definitions?
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Empirical or Theoretical
Information?
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Both empirical and theoretical
information is used to form the above
definitions. Can you pick out what
information is empirical on the previous
slide?
Definitions of Ionic and Molecular
Compounds
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Ionic Compounds
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all solid at SATP
aqueous solutions conduct electricity
transfer of electrons when forming bonds
metal-nonmetal
Molecular Compounds
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solid, liquid and gases at SATP
aqueous solutions do not conduct electricity
share electrons when forming bonds
nonmetal-nonmetal
Lab Exercise
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In science, it is not uncommon for new
evidence to conflict with widely known
and accepted theories. This does not
create a problem but an opportunity to
improve understanding
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Lets test some more compounds and
see if the properties turn out as we would
predict
Investigation
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Lets test some more compounds to support
our empirical definitions for ionic and
molecular compounds
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Evidence Table must include:
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Chemical name
Formula
class
State
Electrical conductivity
Evidence Table
Chemical
Formula
Class
State
Electrical
Conductiv
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Analysis
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Do the properties of the compounds match the
predictions?
Evaluation
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What is judged to be adequate: design, procedure,
and skills?
Are you confident in your results?
Where your predictions correct?
What to do if something does not fit…restrict, revise
or replace?
Restrict, Revise or Replace
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Problem – hydrogen citrate (citric acid)
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C3H4OH(COOH)3
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This is made up of nonmetals so you
would predict a molecular compound but
it conducts electricity, and may be ionic.
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We need to a revision…
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A third class of compounds called ACIDS.
Acids and Bases
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Acids
are solid, liquid or gas as pure compounds
at SATP
 aqueous solutions conduct electricity
 makes blue litmus paper turn red
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Bases
contains hydroxide “OH”
 makes red litmus paper turn blue
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