ATOMS, ELEMENTS, AND
REACTIONS
WHAT IS MATTER?
• Matter is anything that has mass, occupies space,
and can be converted into energy
• Matter has 2 types of properties:
Physical and Chemical
PHYSICAL PROPERTIES OF MATTER
• Can be observed with the 5 senses
• Can be determined without destroying the object
• Examples: color, shape, mass, length, odor , density,
solubility, taste, melting point, hardness, boiling
point, luster, texture
CHEMICAL PROPERTIES OF MATTER
• These indicate how a substance reacts with
something else.
• The original substance is fundamentally changed
while observing a chemical property
• Examples: rusting (oxidation), flammability,
reactions with other substances such as acids or
bases, combustibility
WORK IT…
• Physical and Chemical properties practice
ELEMENTS
WHAT ARE ELEMENTS?
• Elements are PURE substances
• They cannot be broken down into more simple
substances
• They cannot be made by combining other
substances
ATOMS AND ELEMENTS
• If you could look at the atoms in a chemical
element, you would see that they are all the same
type:
Identically built
Identical parts
Identical number of parts
ELEMENT SYMBOLS
Elements are organized and presented in a the periodic
table
Each element on the periodic table has its own box
which includes:
• Its symbol (a capital letter alone or a capital letter & a lower
case number combo)
• Element name
• Atomic number
• Atomic mass
Atomic number
Element
symbol
Element name
Atomic weight
ELEMENT/PERIODIC TABLE ACTIVITY
Safari Videos: “Using the Periodic Table” (25 min.)
“Atomic Structure and the Periodic Table”
(24 min.)
Video: “Hunting the Elements” by Nova on PBS
Activities:
--Element interactive: http://www.funbrain.com/periodic/
--Intro to Periodic Table Activity
--Getting to Know the Periodic Table
COMPOUNDS
QUESTION
• How can only 92 naturally occurring chemical
elements form millions of different types of
materials?
COMPOUNDS!
WHAT ARE COMPOUNDS?
• The substance that is formed when two or more
elements chemically combine in a chemical
reaction
• The new substance formed has different properties
from the original elements
Example of a compound = H2O (water)
Water is made of two gases, hydrogen and oxygen
but is a liquid with its own properties
WHAT ARE COMPOUNDS?
• Compounds always have the same ratio of
elements…water will ALWAYS have two hydrogen
atoms and one oxygen atom
COMPOUNDS
When you have chemical reaction, it is like making a cake.
Your elements are the ingredients and the compound is
the cake. Once you bake the cake a chemical reaction
has taken place….you cannot unmake the cake. It has
turned into another substance!
Safari Video: “Properties of Compounds” (26 minutes)
STRUCTURE OF AN
ATOM
WHAT IS IN ATOMS…WHAT MAKES THEM UP?
WHAT IS AN ATOM?
• An atom is the smallest particle that an element
can be divided into and still BE that element
• Structure of the Atom Worksheet
STRUCTURE OF AN ATOM
Neutrons
Subatomic Particles: Protons,
Neutrons, and Electrons.
• Protons = positively + charged
particles located in the
nucleus
• Neutrons = neutrally O
charged particles located in
the nucleus
• Electrons =negatively charged particles located in
the electron cloud (outside of
the nucleus, surrounding the
nucleus)
Protons
Nucleus
Electrons
ATOMIC THEORY
HOW THE THEORY DEVELOPED INTO
WH A T WE T H I N K T O D A Y
THEORIES IN SCIENCE CHANGE
• As new information is discovered, scientific theories
can change
• Our theory about the atom has changed over time
• Even though no one has actually seen the atom up
close, we are still able to make new discoveries
WHEN DID THE ATOMIC
THEORY START?
• The term “atom” actually comes from the Greek word
“atomos”, which means not able to be divided
• Early theories developed during the ancient Greek
times
DEMOCRITUS
(460-370 BC)
An ancient Greek philosopher
He concluded that there was a limit to how far you could
divide matter. You would eventually end up with a
piece of matter that could not be cut.
He proposed that atoms:
• Are small, hard particles
• They are made of a single material that is formed into
different shapes and sizes
• They are always moving
• They form different materials by joining together
JOHN DALTON
(1776-1844)
• A British chemist and school teacher who rethought
the ideas of Democritus
Dalton’s Ideas:
• All substances are made up of atoms
• Atoms of the same element are exactly alike and
atoms of different elements are different
• Atoms join with other atoms to form different
substances
J.J. THOMSON
(1856-1940)
• Thomson did experiments with cathode ray tubes and
discovered negatively charged particles called electrons
• Thomson did not know how the electrons were
arranged…he believed they were mixed throughout the
atom
• He proposed that the atom was a sphere of positively
charged material with negatively charged electrons
spread throughout like plum pudding (or like a chocolate
chip cookie) –which is why his theory is referred to as the
Plum Pudding Model
EARNEST RUTHERFORD
(1871-1937)
He was awarded the Nobel Prize for Chemistry for his discovery of
alpha particles, positively charged particles emitted from
radioactive elements
He studied J.J. Thompson but did not agree with the plum
pudding model
Rutherford’s Gold Foil Experiment:
http://micro.magnet.fsu.edu/electromag/java/rutherford
Rutherford’s Atomic Theory:
1. Much of an atom is empty space with most matter of an atom
found in a very small, dense part of the atom called the
nucleus
2. Like charges repel so the nucleus must be positive and the
negatively charged electrons much surround the nucleus at a
distance
THE BOHR MODEL OF THE ATOM
• Bohr proposed that electrons move in paths at certain
distances around the nucleus
• Electrons can jump from a path on one level to a path on
another level
http://www.colorado.edu/physics/2000/quantumzone/boh
r.html
MODERN ATOMIC THEORY
Electrons travel in regions called the electronic cloud
You cannot predict exactly where an electron will be
found in the cloud
http://www.fearofphysics.com/Atom/atom3.html
MODERN ATOMIC THEORY
Energy Levels
The energy that an electron has
is based on its location
around the nucleus
Electrons that are closer to the
nucleus have less energy than
those that are farther away
WORK IT….
• Development of Atomic Theory Fill In.
CHEMICAL REACTIONS
WHAT IS A REACTION?
When elements combine
or rearrange to form a
NEW substance,
they are said to REACT.
This process is called a
chemical reaction.
CHEMICAL REACTIONS VIDEO
• Bill Nye
• https://www.youtube.com/watch?v=Rtcf6Pjahec
SEE A REACTION IN “ACTION”
• Elephant toothpaste
HOW DO WE MAKE SUBSTANCE REACT
IN A CHEMICAL REACTION?
1. Sometimes just mixing!…example: mix hydrogen
peroxide and blood then bubbles of carbon dioxide
automatically form!
2. Heating …example: just mixing sulfur (a powdery nonmetal) with the metal iron only results in a mixture but when
heated, a new substance is formed--Iron Sulfide!
3. Mixing with water…example: when dried citric acid and
sodium bicarbonate are dissolved in water, they react to
fizz (Alka-Seltzer)
PLASTIC MILK LAB
Chemical Reaction: Firework Webquest
MIXTURES
• Mixtures are formed when substances are simple
stirred together and NO new substance is formed.
• When we mix sugar and water it seems like it
disappears but we can still separate the water and
sugar through evaporation…both the water and
sugar still exist
• When we mix iron filings and sand you may not be
able to tell which part is sand and which part is iron
filings but we can separate the mixture using a
magnet to attract the iron filings.
KINDS OF MIXTURES
• Homogeneous: a mixture that is uniformly dispersed
(the solute is dissolved in the solvent evenly
throughout the mixture)
(Homo = same)
• Heterogeneous: a mixture in which the solute is not
evenly distributed throughout the mixture
(Hetero = different)
HOW IS A CHEMICAL REACTION
DIFFERENT FROM A MIXTURE?
Chemical
Reactions:
Mixtures:
A new substance is
made
Example: Wood
burning = ashes
No new substances
are formed
Example: Cinnamon
and Sugar
Both:
Two or more
substances
combine
DISSOLVING
To dissolve something means to break up substances into
individual atoms or molecules
Example: sugar or salt can be dissolved in water with stirring
When substance is completely dissolved in another
substance the mixture is called a solution
The substance that is dissolved is called the solute
The substance which the dissolving is INTO is called the
solvent
SEPARATING A MIXTURE activity
DISSOLVING
(Water
)
Solute
Solvent
Solution
ARE SOLUTIONS ALWAYS A
SOLID DISSOLVED IN LIQUID???
NOPE!!!
You can make a solution out of any combination of
liquid, solid, or gas!
Examples:
• alcohol in water (liquid in liquid)
• iodine vapor in air (liquid in gas)
• the air we breath is a solution of various gases
(nitrogen, oxygen, etc.)
HOW CAN WE SHOW A CHEMICAL
REACTION IN WRITING?
A chemical equation is a statement that uses
symbols, chemical formulas, and numbers to stand
for a chemical reaction
Example:
HCl + NaOH
(reactants)
NaCl + H2O
(products)
Reactants are the chemicals added together
Products are the chemicals you end up with!
REVIEW CHEMICAL
REACTIONS/MIXTURES
1. Any change in which substances turn into other
substances is called___________________
2. A combination of substances in which no reaction
takes place __________________
3. When sugar is dissolved in water the water is the:
A) solute
B)solvent C)solution
BALANCING EQUATIONS CAN BE
TRICKY!!!!!
The amount of ingredients you start out with as reactants in
a chemical equation is the amount you have to end up
with.
Now the ingredients may be arranged differently but the
amount of the substances must stay equal the amount you
began with
H+H+O
H 2O
The above equation starts out with two hydrogen and one
oxygen…the product is water but it still ends up with two
hydrogen atoms and one oxygen atom
THE LAW OF THE CONSERVATION OF
MATTER
This law states that matter cannot
be created or destroyed in any
chemical change
BALANCING EQUATIONS
In order to follow the Law of Conservation
we have to make the two sides of a
reaction come out even (balanced) you
can use numbers called coefficients
before the formulas
BALANCING EXAMPLE
Example:
H2 + O2
H 2O
(this equation is NOT balanced because we started out
with two hydrogens and two oxygens but ended up with
two hydrogen but only one oxygen)
But if we add coefficents…
2H2 + O2
2H2O
NOW we start out with two sets of two hydrogen (2x2=4
hydrogen) and two oxygen.
Then we end up with two sets of H2O (2x2=4
hydrogen…2x1=2 oxygen)
REVIEW BALANCING
2Na + Cl2
2NaCl
Look at the above chemical equation to answer the
following questions:
1. What are the reactants?
2. What are the products?
3. Is the equation balanced? Why or why not?
GROUP ACTIVITY: Try to balance these
equations using coefficients...
You have just a few minutes!
[1]
Na + Cl2
[2] CH4 + O2
 NaCl
 CO
[3] Li + HNO3
[4] Al + O2
2
+ H2O
 LiNO
3
 Al O
2
3
+ H2
Why didn’t
anyone tell me
it was so easy
to balance
equations???!!!
How did you get on??
Here are the answers:
[1]
2 Na + Cl2
 2 NaCl
[2] CH4 + 2 O2
 CO
[3] 2 Li + 2 HNO3
[4] 4 Al + 3 O2
+ 2 H2O
2
2
LiNO3 + H2
 2 Al O
2
3
BALANCING EQUATIONS PRACTICE
• Balancing Equations practice worksheet
SYNTHESIS AND DECOMPOSITION
REACTIONS
The word synthesis means “to
combine parts”
If something decomposes, it
breaks down.
SYNTHESIS
In a synthesis reaction two or more
substances combine to form a compound
Example: iron (Fe) and sulfur (S) combine to make the
compound Iron sulfide (FeS)
DECOMPOSITION
In a decomposition reaction a compound breaks
down into two or more simple substances
Example: Sugar (C6H12O6) breaks down into 6 Carbon (6C)
and 6 water (6H2O)
Divorce
SYNTHESIS/DECOMPOSITION
REACTION REVIEW
Decide if the following equations are synthesis or
decomposition reactions:
1. 2MgO
2. 2Hg + O2
3. C + O2
4. BaCl2
2Mg + O2
2HgO
CO2
Ba + Cl
CAN YOU SYNTHESIZE OR DECOMPOSE
SOMETHING?
On a separate piece of paper, draw a
picture of what you would do if…
You wanted to synthesize a burrito
You wanted to decompose a
sandwich, what would you do?
Make sure to turn your drawings into you class’s box
when you are done! Don’t forget to put your name on
it!!
Exothermic Synthesis Reaction Lab
No Leftovers (Decomposition Reaction)
SINGLE-REPLACEMENT AND DOUBLEREPLACEMENT REACTIONS
To help you remember:
Single means 1
Double means 2
SINGLE-REPLACEMENT REACTIONS
• A Single-Replacement Reaction is a reaction in which
one element replaces another in a compound
• Example:
• Cu + 2AgNo3
2Ag + Cu(NO3)2
• This one switches with this one in the product
DOUBLE REPLACEMENT
In a double-replacement reaction, elements in two
compounds are exchanged.
Kind of like square dancing
when you switch partners with each other!
Example:
NaCl + AgNO3
NaNO3 + AgCl