Chemistry basics
Do they matter?
Observations:
Statements of fact about what you see, feel,
smell, taste, hear.
O Qualitative observations are observations
made with words…
O The reaction smells like pumpkin pie.
O The solution is royal blue.
O Quantitative observations are those that
are made with numbers (measurements).
O Scientists seem to prefer these if at all
possible.
O The table is 47.2 inches long.
Inferences: What you believe to be
true, based on your observations.
O Observation: The man is frowning.
O Inference: The man is unhappy.
O Observation: The reaction is producing a
gas.
O Inference: The gas being produced is
hydrogen.
Whatsamatter?
O Matter is stuff. It’s anything that has mass
and volume. Some examples of matter are:
O Cheese
O Badgers!!!
O An idea isn’t matter since it doesn’t have
mass
Matter comes in different
states
O Alaska?
O No!
O Minnesota?
O No!!
O Arizona (A very
warm place)?
O No!!!
The three main states
(phases) of matter are:
O Solid: Definite shape and volume.
O This is because the molecules are tightly
packed and vibrating in place.
O Liquid: Indefinite (changeable) shape but
definite volume.
O This is because the molecules can move in
relation to one another but are still pretty
tightly packed.
O Gas: Indefinite shape and volume.
O Molecules are spaced out and can move freely.
You may be wondering about
that fourth state…
O It is not Utah!
O It is…
O Plasma!!!
Substances can be changed
from one state to another.
O Melting
O The change from solid to liquid.
O Evaporation
O The change from liquid to gas.
O Condensation
O The change from gas to liquid.
O Freezing
O Liquid to solid.
O Sublimation
O The change from a solid directly to
a gas
When a substance changes
state or shape…
O It’s still the same substance
O These changes are called physical
changes. So…
O A physical change is one that changes the
shape or state of a substance without
changing the nature of the substance
itself.
O Cutting, tearing, crumbling…
O Physical changes are usually reversible
Chemical Changes
O Chemical changes are those that cause a
reorganization of atoms and result in the
formation of new substances.
O Chemical reactions result in chemical
changes.
Evidences of chemical
change
O Odor
O Color change
O Gas produced
O Temperature
change
O Precipitate
O Light
Mixtures: Substances are often
found mixed with other substances.
O Mixtures fall into one of two
categories.
O Homogeneous mixtures have the same
composition (make-up) throughout.
O Soda
O Air
O Heterogeneous mixtures have a make-
up that is not the same throughout.
O Oil and vinegar dressing
O Dirt
Remember this?
O Homo = Same
O Hetero = Different
Different ways to separate
mixtures:
O Filtration allows some particles
through a membrane (Remember
your cells have a semi-permeable
membrane?) and keeps others
out.
O Distillation uses differing boiling
points to boil off and separate
different parts of a mixture.
O Chromatography uses differing
polarity and solubility to separate
mixtures
Measuring Volume
O Graduated cylinders are used to
measure specific volumes of liquids.
The glass cylinder has marks to indicate
volumes, a pouring lip, and quite often,
a plastic bumper to prevent breakage.
What is A Meniscus?
O A meniscus is what happens when you put
a liquid into a container. When you put
water in a beaker or test tube, you see a
curved surface.
Reading the Meniscus
The Meniscus: Practice #1
ANSWER
O73.0 mL
10 mL graduated cylinder:
Practice #2
ANSWER
O6.62 mL
100 mL graduated cylinder:
Practice #3
ANSWER
O52.8 mL
25 mL graduated cylinder:
Practice #4
ANSWER
O11.52 mL
100 mL graduated cylinder:
Practice #5
ANSWER
O52.8 mL
Some Measurement Basics
O SI measurement units come from the metric
system:
O Length = Meters (m).
O Other commonly used measures are:
O Centimeter, cm (0.01m)
O Kilometer, km (1000 km)
O Mass = Grams (g).
O Other commonly used unit is the kilogram, kg (1000
g).
O Volume = Liters (L). Other commonly units are:
O Millileter, mL (0.001 L)
O Cubic centimeter, cm3 (0.001 L)
O 1 mL = 1 cm3
Density
O Density is a measurement of the amount of
O
O
O
O
matter in a certain space.
You can think of density as how tightly packed the
atoms or molecules are.
Density = mass/volume
The SI unit for density is g/mL
Pure water has a density of 1.00 g/mL.
O Anything with a density greater than 1.00 g/mL
sinks in water.
O Anything with a density under 1.00 g/mL floats
on water.
O Water’s density is the basis of the metric system!
Scientific notation
O Scientific notation (Called exponential
notation in math) is a way to write very
large or very small numbers without
writing all the zeroes.
O In scientific notation, a number is
written as a number between 1 and 10,
multiplied by some power of ten.
O So 450700 would be written as 4.507 x
105
Mo’ Scientific Notation
O The power of ten is just how many places
you move the decimal point.
O If you move the decimal to the left, the
exponent (power) is positive.
O If you move the decimal to the right, the
exponent is negative.
O 93,000,000,000 is 9.3 x 1010 since you
moved the decimal to the left.
O 0.0000569 is 5.69 x 10-5 since you move
the decimal to the right.
Practice
O Write the following numbers in scientific notation.
O 54
O 5.4 x 101
O 0.00249
O 2.49 x 10-3
O 10006700
O 1.00067 x 107
O 76,000,000,000,000
O 7.6 x 1013
O 0.0000000000084
O 8.4 x 10-12
O 0.327
O 3.27 x 10-1
Individual substances fall in
two categories
O Elements
O Elements are the simplest form of matter
with unique properties. You cannot break
up elements any further (easily).
O Compounds
O Compounds are substances made of two or
more elements, chemically combined.
O A mixture could be made of two or more
elements, but they aren’t chemically
combined!
Symbols and formulas
O Each element has a symbol, kind of like each
state has an abbreviation…
O The symbols make it easier to write out
chemical formulas for things like…
O Water
O H2O
O Methane
O CH4
O Glucose
O C6H12O6
Chemical formulas tell you what
elements are in the compound and
the proportions of atoms of each
element.
O H2O
O 2 hydrogen atoms, 1 oxygen atom
O CH4
O 1 carbon atom, 4 hydrogen atoms
O C6H12O6
O 6 carbon atoms, 12 hydrogen atoms, 6 oxygen atoms
O C2H6O
O 2 carbon atoms, 6 hydrogen atoms, 1 oxygen atom
3HNO3 + C6H10O5 → C6H7(NO2)3O5 + 3H2O
O Some rules for reading chemical formulas
O The symbol tells you the element.
O If the is no subscript it means there is one atom.
O There is one atom of hydrogen in HNO3
O Any other subscript tells you that there are that
number of atoms.
O There are 10 atoms of hydrogen in C6H10O5
O A subscript outside parentheses means there are
that many of the thing in the parentheses.
O There are 3 NO2 units in C6H7(NO2)3O
O A coefficient (number in front) means there are
that number of molecules of a compound.
O There are 3 molecules of H2O
So let’s count the atoms in
3HNO3 + C6H10O5 → C6H7(NO2)3O5 + 3H2O
O 3 HNO3
O 3H
O C6H7(NO2)3O5
O 6C
O 3N
O 7H
O 9O
O 11 O
O C6H10O5
O 6C
O 10 H
O 5O
O 3N
O 3 H 2O
O 6H
O 3O
Counting up those atoms
brings up a nifty law…
O The law of conservation of mass.
O During any chemical reaction, the mass of
the products is always equal to the mass
of the reactants
O Reactants are what goes into the reaction
O Products are what comes out of the
reaction.
3HNO3 + C6H10O5
C6H7(NO2)3O5 + 3H2O
Reactants
Products
Remember our copper
chloride reaction with
aluminum?
O Al + CuCl2 + H2O  Al(OH)3 + AlCl3 + Cu + H2