Transcript Elements, mixtures and compounds lecture

Draw this model now
elements, mixtures, compounds video:
https://www.youtube.com/watch?v=yzGSLA68_Hw
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This is a model of what?
What are the red objects? (label it now)
What is the name of the blue region? (label)
What two objects make up the blue region?
• Everything that exists is made of matter (even
the air you now breathe). So, what is matter?
• Matter is anything which has both mass and
volume. Are ideas matter?
• Matter is made of atoms which can be arranged
in almost infinite ways to make the world as we
know it (brick houses?)
• Atoms are on the order of a trillionth of a meter
in size: 10-10 meters
• Atoms are constantly moving in irregular-jerky
like motion called Brownian motion (model?)
• So, though you may have a solid material, in
fact at the atomic level atoms are moving quite
vigorously but you cannot see/feel the motion!
I. Element (ie: oxygen, hydrogen, lead, gold, krypton):
A. exists as only one type of atom: it is, therefore a
pure substance (This does not often occur in
nature); gold necklace?
Oxygen is the most common pure element on Earth
(occurs as a dioxide: O2 , what does “di” mean?)
B. cannot be broken down by chemical reactions:
burning/acids/eating (but nuclear rxns: yes!)
C. There are some 118 elements (this # changes
as we discover new elements), 90 of these are
naturally occurring, 22 are synthetic (?)
D. two large groupings:
metals and
nonmetals (which is the larger group?)
E. they can ALL occur as different energy
states: solid, liquid, gas or plasma: gold  gas?
F. symbology:
1. abbreviated by a unique letter
which is capitalized,
if there is a second letter it is lower case: Cu
oxygen = O
hydrogen = H
helium = He
lead = Pb (?)
gold = Au (?)
NOTE: Latin is the basis for the symbol:
dead language thus it does not
change:
world-wide use
Draw and label this now
What element is this
What is the easiest way to find it on the periodic table?
79
196.9
2. the atomic number defines the
element:
it is unique: no other element has
that number! (like DNA is to the living)
3. the atomic # also identifies the
number of protons per atom
(located in the nucleus)
So, atomic # = # protons per atom
G. each element has its own physical and
chemical properties: characteristic properties, thus
these characteristics properties can be used to
identify and separate elements, such as
the temperature of a phase change to separate
water from alcohol (distillation) or as in forensics
2. Mixture (ie: ocean, air, lemonade):
A. two or more physically combined
substances (elements or compounds):
NOT chemically combined! Thus, there are no
bonds between substances: salt & pepper
B. not a pure substance (pure substance
cannot be separated by physical means)
C. their individual substances retain their own
characteristic properties, thus can use their c.p.
to separate them: tap water, air?
D. use physical means to separate mixture: filter,
dehydrate (salt water), density, sort (salt & pepper)
E. two categories of mixtures:
1. homogeneous mixture: equal distribution of
each substance (sugar cookie): lemonade?
2. heterogeneous mixture: unequal
distribution of each substance (chocolate
chip cookie): lemonade?
Mixture of colors:
Mixture or compound?
Homo or heterogeneous?
3. Compound (ie: water, wood, most of what is around us!)
A. most individual atoms of elements are unstable (reactive: like
freshmen!),
and thus want to chemically combine to form stable new
substances (like seniors are) by creating:
chemical bonds (ie: magnets?; HCl + Mg  MgCl + H2)
B. the new substance has new and different characteristic
properties: H2O, NaCl, MgCl?
C. atoms always combine in definite proportions:
this is called a chemical formula:
1. 3H2O ?
2. tells the # of molecules (3) and # of atoms (9)
3. coefficient = # molecules: 3
three H2O molecules: H2O + H2O + H2O
4. subscript (sub ?) = # atoms of only that atom: 2
H2 = two hydrogen atoms
3H2 = 6 atoms
Compound of table salt (NaCl):
D. two groups of compounds,
based on how they combine:
1. molecular: atoms share electrons, ie: H2O
2. ionic: atoms gain or lose electrons,
becoming a “charged atom”:
*gain e- and become negative (anion)
*lose e- and become positive (cation)
a. most are solids and soluble in water
b. ie: NaCl (table salt)