Transcript Composition of Matter

Composition of Matter
All matter is composed of Atoms
Protons



Found in the nucleus
of atom
positive (+) charge
Mass Value  1
Neutrons



found in nucleus of
atom
neutral (no) charge
Mass value  1
Electrons



found in clouds
orbiting around
nucleus
negative (-) charge
Mass value  0
Periodic Table of Elements
Each element is made up of same atoms
1
H
Hydrogen
1.0079
Atomic Number = Number of Protons
(# P = # of electrons)
Symbol – 1st letter always CAPITAL
2nd letter always lower cased
Name
Atomic Mass = Number of Protons
+ Number of Neutrons
Number of Neutrons = Atomic Mass - Atomic Number
Number of electrons must equal the number protons
or the atom will be charged (+ or -) = Ion
Atomic Models
Most often represented as series of circles
Center circle represents
the nucleus - containing the
protons (P+)and neutrons (N)
Outer circles represent
the electron clouds where
electrons (e-) orbit
Bohr’s Model
Each valence (orbit) has a
specific number of electrons
it can hold
ee6P
 1st holds up to 2 e-
e-
6N
 2nd holds up to 8 e 3rd holds up to 8 e 4th holds up to 18 e-
eeCarbon atom
e-
Must remember that:
 Bohr’s Models are
simple 2D models
Atoms are actually 3D
 Electrons actually
move around nucleus
in an electron cloud not
a linear orbit
 Atoms are active –
drawings are
stationary
Lewis Dot Model
 Uses dots to show Valance electrons –
outermost orbit
 Valence Electrons are the ones that make
the atom interactive
 Arranged in pairs on 4 sides of symbol –
Shows “empty seats”

 N

Why do Atoms React?
 They want to fill their “empty seats” on
valence orbit
 Nitrogen has 3 “empty seats”


Can add or lose electrons  IONic bond
Can share electrons  Covalent

X
X N
X
Types of Bonds
Ionic Bonds
 Atoms may gain or
lose electrons to fill
its valence shell
 This creates an
imbalance of + and –
creating a charged
atom or ION
 Opposites attract
 Ex Na+Cl-
Covalent Bonds
 Atoms may share
electrons to fill
valence shell
 ex. H2O
Hydrogen Bonds
 Occur between H
(only have 1 electron)
 weak bond
 Ex surface tension
between H2O molecules
Why is Carbon so Important?
• Carbon has 6 protons;
therefore has 6 electrons
• This leaves 4 empty seats
for Carbon to fill
• Carbon will bond with
LOTS of things BUT likes
to bind with other C
atoms.
• This creates the rings and
chains of all the organic
compounds
Molecules and Compounds
MOLECULE – 2 definitions
1)
2 or more atoms of the same element
joined together
2)
O2; H2; O3
Smallest unit of a compound that has the
properties of that compound
COMPOUND
2 or more different elements chemically
combined
H2O; CO2; C6H12O6
Polarity of Water
Water (H2O) is made up of 2 H and 1 O sharing
their electrons (covalent bond)
There is a higher concentration of electrons on
the Oxygen end making it slightly negative
and the Hydrogen end slightly positive
Lipids are insoluble in water
Because they are
• Not polar
• Have no ionic
bonds
Therefore, they are
NOT attracted to
water
pH
The concentration of H+ in a solution
 measures the acidity or basicity of the solution
 H2O will break apart creating hydrogen ions
(H+ ) and hydronium ions (OH-)
 More H+ = acid (< 7)
 More OH- = basic (alkaline) (>7)
 Equal amounts H+ & OH- = Neutral (pH7)
States of Matter:
Matter on Earth can be found in three states:
 SOLIDS – molecules are barely moving;
(ice cube)
 Little
energy
 Definite volume
 Definite Shape
States of Matter
 LIQUIDS - molecules moving fairly freely
(water)
 More
energy
 Definite volume
 No definite shape
States of Matter
 GASES – molecules are moving rapidly
(steam)
 Lots
of energy
 No definite volume
 No definite shape
Physical
Change
How do you know you saw a
PHYSICAL CHANGE?
Change in:
State, shape or size…
Change in STATE
Liquid
Solid
Gas
Change in SIZE
Change in SHAPE
Chemical
Change
How can you tell there was a
CHEMICAL REACTION!? Something
NEW is formed…
New
solid formed
Precipitate
Unexpected
color change
Clear + Clear 
PURPLE
Temperature
change
Increase (endothermic)
or
Decrease (exothermic)
New gas
formed
Bubbles
Odor/smell
Steam
Quiz –
Identify as Chemical or Physical Change
Slicing bread
Rust on nail
Baking bread
Melting Ice cream
Physical
Chemical
Chemical
Physical