Physical Science EOCT Review
Domain 2: ChemistryChemical Reactions and
Properties of Matter
Domain 2: Chemistry- Matter
Matter
• Matter is anything that: a) has
mass, and b) takes up space
• 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
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.
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. (Which is correct: water gas,
or water vapor?)
States of Matter
Definite Definite
Volume? Shape?
Solid
Liquid
Gas
YES
YES
NO
Result of a
Temperature Will it
Compress?
Increase?
YES
Small
Expans.
NO
NO
Small
Expans.
NO
NO
Large
Expans.
YES
4th state: Plasma - formed at
high temperatures; ionized phase
of matter as found in the sun
Condense
Freeze
Evaporate
Melt
Solid
Liquid
Gas
Physical vs. Chemical Change
• Physical change will change the
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
• 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
•
Chocolate chip cookie, gravel, soil.
2) Homogeneous - same composition
throughout; called “solutions”
•
Kool-aid, air, salt water
• Every part keeps it’s own properties.
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 a solid from
the liquid in a heterogeneous
mixture (by size) – Figure 2.7, page 46
Substances
• Elements- simplest kind of matter
– cannot be broken down any simpler
– 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!)
Compound or Mixture?
Compound
Mixture
Made of one kind
of material
Made of more than
one kind of material
Made by a
chemical change
Made by a
physical change
Definite
composition
Variable
composition
Which is it?
Mixture
Element
Compound
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.
Classification of Matter
Domain 2: ChemistryChemical Reactions
Naming cations
• Two methods can clarify when
more than one charge is possible:
1) Stock system – uses roman
numerals in parenthesis to
indicate the numerical value
Naming cations
• We will use the Stock system.
• Cation - if the charge is always the
same (like in the Group A metals) just
write the name of the metal.
• Transition metals can have more
than one type of charge.
• Indicate their charge with roman
numerals in parenthesis after the
name of the metal
Naming Anions
• Anions are always the same
charge
• Change the monatomic
element ending to – ide
• F1- a Fluorine atom
becomes a Fluoride ion.
Polyatomic ions are…
• Groups of atoms that stay together and
have an overall charge, and one name.
• Usually end in –ate or -ite
• Acetate: C2H3O21• Nitrate: NO31• Nitrite:
NO21-
• Permanganate: MnO41• Hydroxide: OH1- and Cyanide: CN1-?
Writing Ionic Compound
Formulas
Example: Barium nitrate
1. Write the formulas for the
cation and anion, including
CHARGES!
2+
Ba ( NO3- )2
2. Check to see if charges are
balanced.
3. Balance charges , if necessary,
using subscripts. Use parentheses if
you need more than one of a
polyatomic ion. Use the criss-cross
method to balance subscripts.
Now balanced.
Not balanced!
= Ba(NO3)2
Writing Ionic Compound
Formulas
Example: Iron (III) chloride
1. Write the formulas for the
cation and anion, including
CHARGES!
Fe3+ Cl3
2. Check to see if charges
are balanced.
3. Balance charges , if necessary,
using subscripts. Use parentheses if
you need more than one of a
polyatomic ion. Use the criss-cross
method to balance the subscripts.
3
Now balanced.
Not balanced!
= FeCl3
Writing Ionic Compound
Formulas
Example: Magnesium carbonate
1. Write the formulas for the
cation and anion, including
CHARGES!
2. Check to see if charges
are balanced.
Mg2+ CO32They are balanced!
= MgCO3
Naming Ionic Compounds
• 1. Name the cation first, then anion
• 2. Monatomic cation = name of the
element
Ca2+ = calcium ion
• 3. Monatomic anion = root + -ide
Cl− = chloride
CaCl2 = calcium chloride
Naming Ionic Compounds
(Metals with multiple oxidation states)
• some metals can form more than one
charge (usually the transition metals)
• use a Roman numeral in their name:
PbCl2 – use the anion to find the charge
on the cation (chloride is always 1-)
Pb2+ is the lead (II) cation
PbCl2 = lead (II) chloride
Things to look for
• If cations have (_), the number
in parenthesis is their charge.
• If anions end in -ide they are
probably off the periodic table
(Monoatomic)
• If anion ends in -ate or –ite,
then it is polyatomic
Molecular compounds are…
• made of just nonmetals
• smallest piece is a molecule
• can’t be held together
because of opposite charges.
• can’t use charges to figure out
how many of each atom
Molecular compounds are easier!
• Ionic compounds use charges to
determine how many of each.
–Have to figure out charges.
–May need to criss-cross numbers.
• Molecular compounds: the name
tells you the number of atoms.
• Uses prefixes to tell you the exact
number of each element present!
Prefixes (Table 9.4, p.269)
•
•
•
•
•
•
•
•
1 = mono2 = di3 = tri4 = tetra5 = penta6 = hexa7 = hepta8 = octa-
Prefixes
• 9 = nona• 10 = deca• To write the name, write two words:
Prefix name Prefix name -ide
• One exception is we don’t write mono- if
there is only one of the first element.
• Normally do not have double vowels
when writing names (oa oo)
Practice by naming these:
•
•
•
•
•
•
N2O
MgCO3
Cl2O7
TiS
CO2
BaCl2
Write formulas for these:
•
•
•
•
•
•
•
diphosphorus pentoxide
tetraiodine nonoxide
Iron (III) oxide
nitrogen trioxide
Calcium sulfide
Potassium iodide
aluminum chloride
Chemical Reactions are…
• When one or more substances are
changed into new substances.
• Reactants- the stuff you start with
• Products- what you make
• The products will have NEW
PROPERTIES different from the
reactants you started with
• Arrow points from the reactants to the
new products
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
4. Balanced Chemical Equations
• Atoms can’t be created or
destroyed in an ordinary
reaction:
–All the atoms we start with we must
end up with
• A balanced equation has the
same number of each element on
both sides of the equation.
Rules for balancing:
1) Assemble the correct formulas for all the
reactants and products, use + and →
2) Count the number of atoms of each type
appearing on both sides
3) Balance the elements one at a time by
adding coefficients where needed (the
numbers in front) - save balancing the H
and O until LAST!
(I prefer to save O until the very last)
4) Check to make sure it is balanced.
• Never change a subscript to balance an
equation.
– If you change the formula you are describing a
different reaction.
– H2O is a different compound than H2O2
• Never put a coefficient in the middle of a
formula
2NaCl is okay, but Na2Cl is not.
Types of Chemical Reactions
• Combination A+B AB
• Decoposition AB A + B
• Single Replacement AB + C AC + B
or
A + BC AC + B
• Double Replacement AB + CD AD + CB
• Combustion CH(O) + O2 CO2 + H20
• If O2 limited CH(O) + O2 CO + H20
• If O2 limited CH(O) + O2 C + H20
#1 - Combination Reactions
• Combine = put together
• 2 substances combine to make one
compound.
• Ca +O2 → CaO
• SO3 + H2O → H2SO4
• We can predict the products if the
reactants are two elements.
• Mg + N2 → ____
#2 - Decomposition Reactions
• decompose = fall apart
• one reactant breaks apart into
two or more elements or
compounds.
electricity
  →
• NaCl  ∆→
Na + Cl2
• CaCO3
CaO + CO2
• Note that energy (heat, sunlight,
electricity, etc.) is usually
required
#3 - Single Replacement
• One element replaces another
• Reactants must be an element
and a compound.
• Products will be a different
element and a different
compound.
• Na + KCl → K + NaCl
• F2 + LiCl → LiF + Cl2
#4 - Double Replacement
• Two things replace each other.
– Reactants must be two ionic compounds.
– Usually in aqueous solution
• NaOH + FeCl3 →
– The positive ions change place.
• NaOH + FeCl3 → Fe+3 OH- + Na+1 Cl-1
• NaOH + FeCl3 → Fe(OH)3 + NaCl
#5 - Combustion
• Means “add oxygen”
• Normally, a compound composed
of only C, H, (and maybe O) is
reacted with oxygen – usually
called “burning”
• If the combustion is complete, the
products will be CO2 and H2O.
• If the combustion is incomplete,
the products will be CO (or
possibly just C) and H2O.
Domain 2: ChemistryProperties of Matter
Solvents and Solutes
• Solution - a homogenous mixture, that
is mixed molecule by molecule.
• Solvent - the dissolving medium
• Solute -the dissolved particles
• Aqueous solution- a solution with water
as the solvent.
• Particle size less than 1 nm; cannot be
separated by filtration – Fig. 15.6, p.450
Parts of a Solution:
1. Solute
A solute is the dissolved substance in a
solution.
Salt in salt water
Sugar in soda drinks
Carbon dioxide in soda drinks
2. Solvent
A solvent is the dissolving medium in a
solution.
Water in salt water
Water in soda
Dissolution of Solid Solute
What are the driving forces which
cause solutes to dissolve to form
solutions?
1. Covalent solutes dissolve by H-bonding to
water
2. Ionic solutes dissolve by dissociation into
their ions.
These ions have
been surrounded
by water, and are
now dissolved!
• Solids will dissolve if the attractive force
of the water molecules is stronger than
the attractive force of the crystal.
• If not, the solids are insoluble.
• Water doesn’t dissolve nonpolar
molecules (like oil) because the water
molecules can’t hold onto them.
• The water molecules hold onto other
water molecules, and separate from the
nonpolar molecules.
• Nonpolars? No repulsion between them
Electrolytes and Nonelectrolytes
• Electrolytes- compounds that conduct
an electric current in aqueous solution,
or in the molten state
– all ionic compounds are electrolytes
because they dissociate into ions (they are
also called “salts”)
• barium sulfate- will conduct when
molten, but is insoluble in water!
Electrolytes and Nonelectrolytes
• Do not conduct? = Nonelectrolytes.
– Most are molecular materials,
because they do not have ions
• Not all electrolytes conduct to the
same degree
– there are weak electrolytes, and
strong electrolytes
– depends on: degree of ionization
Solution formation
•
The “nature” (polarity or composition) of
the solute and the solvent will
determine…
1. Whether a substance will dissolve
2. How much will dissolve
•
Factors determining rate of solution...
1. stirring (agitation)
2. surface area the dissolving particles
3. temperature
Making solutions
• In order to dissolve, the solvent
molecules must come in contact
with the solute.
1. Stirring moves fresh solvent into
contact with the solute.
2. Smaller pieces increase the amount
of surface area of the solute.
- think of how fast a breath mint
dissolves when you chew it
Temperature and Solutions
3. Higher temperature makes the
molecules of the solvent move
around faster and contact the
solute harder and more often.
– Speeds up dissolving.
• Higher Temperature Also Usually
increases the amount that will
dissolve (an exception is gases)
Domain 2: Chemistry- Acids
and Bases
Properties of acids
• Taste sour (don’t try this at home).
• Conduct electricity.
– Can be strong or weak electrolytes in
aqueous solution
• React with metals to form H2 gas.
• Change the color of indicators (blue
litmus to red).
• React with bases (hydroxides) to form
water and a salt.
Acids Affect Indicators
Blue litmus paper turns red in
contact with an acid.
Acids have a pH less than 7
Acids Neutralize Bases
HCl + NaOH → NaCl + H2O
-Neutralization reactions
ALWAYS produce a salt and
water.
-Of course, it takes the right
proportion of acid and base
to produce a neutral salt
Properties of bases
• React with acids to form water
and a salt.
• Taste bitter.
• Feel slippery (don’t try this either).
• Can be strong or weak
electrolytes in aqueous solution
• Change the color of indicators
(red litmus turns blue).
Bases Affect Indicators
Red litmus paper
turns blue in contact
with a base.
Phenolphthalein
turns purple in a
base.
Bases
have a
pH
greater
than 7
Bases Neutralize Acids
Milk of Magnesia contains
magnesium hydroxide,
Mg(OH)2, which neutralizes
stomach acid, HCl.
2 HCl + Mg(OH)2
MgCl2 + 2 H2O