CHANGES IN MATTER: PHYSICAL
AND CHEMICAL CHANGES
EQ: How are changes in matter related to changes
in energy?
CHANGES IN MATTER
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You are at the beach
You built a sandcastle!
You notice storm clouds gathering in the distance.
You are sad : (
You know your sandcastle is about to go bye-bye.
You look at your shoulders,
You are getting sunburned.
The creation of sand art, the gathering clouds and
your sunburn are all examples of changes in matter.
Chemistry is mostly the study of the changes in
matter.
We will be studying these changes as we answer the
question: How are changes in matter related to
changes in energy?
PHYSICAL CHANGES
In what ways can
matter change?
 A physical change is
any change that alters
the form or
appearance of matter.
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But does not make
any substance in the
matter into a
difference substance.
PHYSICAL CHANGES
For example, when
making your
sandcastle, you
changed your formless
pile of sand into a
work of art.
 However, despite the
change in form, the
sand is still sand.
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PHYSICAL CHANGES--MATTER CAN PHYSICALLY CHANGE IN SEVERAL
WAYS
Change of State
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Matter occurs in four states: solids,
liquids, gases and plasma.
Suppose you leave a puddle of liquid
water on your kitchen counter (bad
8th grader!)
When you come back, the puddle is
gone!
What happened?
Did the liquid disappear?
Did your mother wipe it up for you
(bad 8th grader!)?
It may have evaporated and become
water vapor, a gas.
A change in state, from a liquid to a
gas is an example of a physical
change.
The water is still water.
Examples: melting, freezing,
condensing, evaporating,
sublimating
Change in Shape or Form
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Is there a physical change
when you make sweet tea the
right way?
To be sure, you would need to
know if the sugar has been
changed into a different
substance.
If you pour the tea into a pan,
boil the solution dry, you
would find a sugar crust at the
bottom.
The sugar looks different, but it
is still sugar.
Other physical changes are:
bending, crushing, breaking,
chopping, dissolving, distilling
CHEMICAL CHANGES
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Chemical changes happen on a
much smaller scale.
While some experiments show
obvious chemical changes, such
as a color change, most
chemical changes are not
visible.
A change in matter that
produces one or more new
substances is called a chemical
change, or a chemical reaction.
In some chemical changes, a
single substance simply
changes to one or more
substances.
In other chemical changes, two
or more substances combine to
form different substances.
CHEMICAL CHANGES
One substance changes
to one or more other
substances
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Hydrogen peroxide (H2O2) when
poured on to a cut on your skin,
it breaks down into water (H2O)
and oxygen gas (O2)
The chemical change as
hydrogen peroxide becomes
water cannot be seen since both
liquids are clear.
However, behind the scenes,
billions of chemical bonds are
being created and destroyed.
In this example, you may see
bubbles of oxygen (O2) gas.
Those bubbles are evidence of
the chemical changes.
Two substances combine
to form different
substances.
 Iron (Fe) rusts when it is exposed
to oxygen gas in the air.
 You can watch the process
happen over a long period of time.
 The molecules change their
structure as the iron is oxidized,
eventually becoming iron oxide
(Fe2O3)
 Rusty pipes in abandoned
buildings are real world examples
of the oxidation process.
EVIDENCE OF CHEMICAL CHANGES
Chemical Changes
involve a change in
chemical composition
in the substances and
something new is
formed.
 These changes are
difficult to reverse
 Some signs (or
evidence) of chemical
change are:
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Bubbling
 Light given off
 Change in
temperature
 Color change
 New odor
 Decomposition
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ENDOTHERMIC AND EXOTHERMIC
CHANGES
When matter
changes, the most
common form of
energy released or
absorbed is thermal
(heat) energy.
 For example, ice
absorbs energy from
its surroundings as it
melts.
 The melting of ice is
called an endothermic
change.
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ENDOTHERMIC AND EXOTHERMIC
CHANGES
An endothermic
change is a change in
which energy is taken
in/absorbed.
 Examples:
 Melting
 Evaporation
 Boiling
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ENDOTHERMIC AND EXOTHERMIC
CHANGES
Changes in matter
can also occur when
energy is given off
 Exothermic changes
are chemical reactions
that produce heat
 Examples:
 Combustion
 Steam condensing to
liquid water
 Fire
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PHYSICAL AND CHEMICAL
CHANGES SORT
EQ: How are changes in matter related to changes in
energy?
http://glencoe.mheducation.com/sites/dl/free/00786004
72/160350/00044680.html
Physical Change
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Chemical Change
No new substance
formed
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At least one new
substance.
Temporary
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No change in the mass
of the substances
undergoing changes
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Permanent
Mass/ matter in =
mass/matter out
CHANGES IN MATTER --- LAW OF
CONSERVATION OF
MASS/MATTER
EQ: How are changes in matter related to changes
in energy?
CONSERVATION OF MASS/MATTER
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A candle may seem to “go
away” when it’s burned or
water may seem to
“disappear” when it changes
into a gas.
However, scientists proved
otherwise long ago.
The Law of Conservation of
Mass/Matter states that
matter is neither created
nor destroyed in any
chemical or physical change.
The mass of the stuff that
you make in a chemical
reaction is the same as the
mass of the stuff that you
start with
LAW OF CONSERVATION OF MASS/MATTER
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For example --- my
world’s famous chili:
Despite the cutting,
chopping, dicing,
browning and
simmering …
The mass of the chili
I serve is equal to the
mass of the
ingredients I put into
the chili.
As it is with chili, so it is
with chemical reactions.
BALANCING CHEMICAL EQUATIONS
One way to show this
rearrangement of
molecules is to
balance a chemical
equation.
 When you balance an
equation, it is easy to
see how atoms are not
lost during a chemical
change, but that they
are rearranged
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BALANCING CHEMICAL EQUATIONS
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There are four easy steps that you need to follow to make this work. Here
they are:
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1. Get yourself an unbalanced equation.
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2. Draw boxes around all the chemical formulas.
Never, ever, change anything inside the boxes. Ever. Really. If you do, you're
guaranteed to get the answer wrong.
3. Make an element inventory.
How are you going to know if the equation is balanced if you don't actually make a list
of how many of each atom you have? You won't.
You have to make an inventory of how many atoms of each element you have, and then
you have to keep it current throughout the whole problem.
4. Write numbers in front of each of the boxes until the inventory for each element is the
same both before and after the reaction.
Whenever you change a number, make sure to update the inventory - otherwise, you
run the risk of balancing it incorrectly.
When all the numbers in the inventory balance, then the equation can balance, and
you can relax
BALANCING CHEMICAL EQUATIONS
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You know why you need
to balance chemical
equations, but you don't
yet know how to do it.
It turns out that I'm
star who knows how to
explain things in a way
that even the dumbest
people know how to
follow.
And, hey, if the dumbest
people can figure it out,
so can you!
BALANCING CHEMICAL EQUATIONS
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Step : 1 Get yourself an unbalanced equation
Done!
BALANCING CHEMICAL EQUATIONS
Step 2: Draw boxes around all the chemical
formulas.
 This is the step that people frequently don't do.
Do it. It makes the difference!
 You're drawing those boxes so that you'll be sure
not to mess around with the formulas to balance
the equation. While they all suffer, you'll be
laughing.
 Here's what the equation looks like:
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BALANCING CHEMICAL EQUATIONS
Step 3: Make an
element inventory.
 In this inventory, your
job is to figure out
how many atoms of
each element you have
on the left and right
sides of the equation.
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BALANCING CHEMICAL EQUATIONS
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Step 4: Write numbers
in front of each of the
boxes until the inventory
for each element is the
same both before and
after the reaction
When we put a number
in front of a formula
anything in that box is
multiplied by that
number, because we're
saying that we have
that many of that kind
of molecule.
BALANCING CHEMICAL EQUATIONS
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So, looking at the inventory,
what should we do?
Well, we can see that on the
left side of the inventory,
there is one atom of sodium
and on the right there are
two.
The solution: Stick a "2" in
front of the sodium
hydroxide (NaOH) on the
left side of the equation so
that the numbers of sodium
(Na) atoms are the same on
both sides of the equation.
When we do this, the new
atom inventory should look
like the figure to the right
BALANCING CHEMICAL EQUATIONS
Now what?
 Looking at the new
inventory, we can see
that we now have two
sodium atoms on both
the left and the right
sides, but the others
still don't match up.
 What to do?
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BALANCING CHEMICAL EQUATIONS
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You can see from the
inventory that on the right
side of the equation, there
are two hydrogen (H)
atoms and on the left there
are four.
Using your amazing
powers of mathematics
(and hopefully you can see
that two multiplied by the
number two becomes four.
That's what you need to
do.
How?
BALANCING CHEMICAL EQUATIONS
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Put a "2" in front of the
water on the right side of
the equation to make the
hydrogens (H) balance out.
Now that this is done, you
should make a new
inventory that looks
something like the figure
on the right
Since both sides of the
inventory match, the
equation is now balanced!
All other equations will
balance in exactly the
same way, though it might
take a few more steps in
some cases.
BALANCING CHEMICAL EQUATIONS
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Step 1 :Get yourself an
unbalanced equation
Step 2: Draw boxes
around all the chemical
formulas.
Step 3: Make an
element inventory.
Step 4: Write numbers
in front of each of the
boxes until the
inventory for each
element is the same
both before and after
the reaction
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NaCl + BeF2 --> NaF +BeCl2
BALANCING CHEMICAL EQUATIONS
NaCl + BeF2 --> NaF +BeCl2
 Answer:
 2 NaCl + BeF -2-> 2 NaF + BeCl2
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BALANCING CHEMICAL EQUATIONS
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CH4 + O 2-> CO2 + H 2 O
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Step 1 :Get yourself an
unbalanced equation
Step 2: Draw boxes
around all the chemical
formulas.
Step 3: Make an
element inventory.
Step 4: Write numbers
in front of each of the
boxes until the
inventory for each
element is the same
both before and after
the reaction
BALANCING CHEMICAL EQUATIONS
CH4 + O 2-> CO2 + H 2 O
 Answer:
 CH4+ 2 O 2 --> CO2 + 2 H 2 O
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LAW OF CONSERVATION OF MASS/MATTER
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Suppose you could collect
all the carbon dioxide and
water produced when
methane burns, and you
measured the mass of all
this matter.
You would find that it
equaled the mass of the
original methane, plus the
mass of the oxygen that
was used in the burning.
No mass was lost, because
in a chemically change,
atoms are not lost or
gained, just simply
rearranged.
CHANGES IN MATTER: ENERGY
AND MATTER
EQ: How are changes in matter related to
changes in energy?
ENERGY AND MATTER
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Everyone has cooked
something at one time or
another,
You may have wondered
why it takes any time at
all to cook the food.
Why can't you just have
instantly cooked potatoes
every time?
And, you may have also
wondered why you needed
to get the food hot in order
to cook it.
Well, both of these
questions can be answered
through chemical change
concepts.
ENERGY AND MATTER
Like matter, energy is
never created nor
destroyed.
 The Law of
Conservation of
Energy states that
energy is never
created nor destroyed,
it’s changed into
another form.
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FORMS OF ENERGY
How do you know if
something has
energy?
 You know if someone
is running has energy
because it is moving.
 But how about the
light and heat from a
burning candle?
 How do you know it
has energy?
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ENERGY AND MATTER
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We know that energy is
the ability to do work or
cause change.
In the first unit, we
focused on energy and
the ability to do work.
In this unit, we will
focus on energy and its
ability to cause change.
We use energy to
physically and
chemically change
matter
FORMS OF ENERGY
The forms of energy
that can change
matter are:
 Kinetic
 Potential
 Thermal
 Chemical
 Electromagnetic
 Electrical
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FORMS OF ENERGY
Kinetic
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Energy of matter in
motion.
Rolling bowling ball
Running
Molecules moving faster
when they are being
heated – changing state
of matter.
Atoms and molecules
chemically combining to
form new compounds –
chemical change
Potential
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Energy an object has
due to its position
Stored energy
Bike at the top of a hill.
During a change of state
of matter, the energy
needed to change goes
into increasing the total
potential energy stored
in the chemical bonds
between the molecules.
FORMS OF ENERGY --- THERMAL (HEAT)
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The most common form
of energy released or
absorbed by matter.
Total energy of the all
particles in an object
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Higher heat = higher
energy
Used to describe the
temperature of
something.
Heat is not the same as
temperature!
Always flows from the
warmer matter to the
cooler matter
CHANGES IN MATTER – THERMAL/HEAT
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You need heat to make the
uncooked food become cooked food.
If you don't add heat, then you
won't be able to make your baked
potato soft or your hard-boiled egg
hard!
When you increase the temperature
of the food, you increase the speed
of the molecules in a food.
The greater their speed, the more
they collide.
These collisions between the
molecules can lead to changes in
molecular structures by creating
new molecules. These new
molecules have different
characteristic colors, flavors, and
textures from the original ones.
The formation of new molecules is
called a chemical reaction.
FORMS OF ENERGY --- CHEMICAL
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Almost anything you touch, see
or taste is composed of chemical
compounds.
The chemical compounds are
made up of molecules and
atoms
Bonds between the atom and
the molecules hold chemical
compounds together.
Those bonds have a chemical
energy.
Chemical energy is stored in
the matches you light up, the
food you eat and even in the
cells in your body.
When bonds in chemical
compound break, some new
chemical compounds are able to
form.
When this happens, chemical
energy is able to be released.
FORMS OF ENERGY -- CHEMICAL
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Chemical reactions have a set speed
There is very little you can do to
speed up a reaction without adding
heat to raise the temperature.
Since hard-boiling eggs (physical
change) occurs in a pot of boiling
water, adding heat to the pot will
only cause the water to boil faster,
but not cook the egg any faster.
This is because the boiling
temperature of water will not
change unless either something is
added to the water
Adding salt to water will increase
the boiling temperature of the
water (chemical change)
Salt, when present in water, lowers
the freezing point (causing snow
and ice to melt) and raises the
boiling point.
FORMS OF ENERGY -- CHEMICAL
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Cooking brings about
chemical changes in
food.
The texture and taste
changes when food is
cooked.
Baking powder contains
sodium
hydrogencarbonate.
This breaks down when
heated, releasing carbon
dioxide that helps cake
mixtures to rise during
baking.
FORMS OF ENERGY --- ELECTROMAGNETIC
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Electromagnetic energy
travels in waves.
In theses waves, the
waves have some electrical
properties and some
magnetic properties.
Some examples for
electromagnetic energy
would be:
Sunlight: photosynthesis -- chemical change
A microwave : defrosting -physical change
FORMS OF ENERGY --- ELECTRICAL
Electrical energy is
the energy of
electrically charged
particles moving from
one place to another.
 When an electric
current is passed
through the filament
of a bulb, the filament
starts glowing and the
glow stops as soon as
the current is cut off –
physical change
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LAB: THE ROLE OF ENERGY IN
COOKING
EQ: How are changes in matter related to changes
in energy?
PHYSICAL AND CHEMICAL CHANGES
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The energy used while cooking brings about
both physical and chemical changes in food.
Physical changes: may be reversible
State of matter (solid to liquid, liquid to gas, liquid to
solid)
Shape and form
Chemical changes: hard to reverse
New substances are formed when different
ingredients are combined
Taste
Texture
Odor
EVIDENCE OF CHANGE
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As these changes occur, evidence may be shown
Physical: may be reversible
New state of matter
New color
New shape or form
New temperature
Chemical: hard to reverse
Bubbling
New color – bread turns brown when toasted. Sugars in
the bread break down when heated.
New temperature
New odor
New taste
New texture
LAW OF CONSERVATION OF MASS/MATTER
The Law of Conservation of Mass/Matter states
that matter is neither created nor destroyed
in any chemical or physical change.
 No mass was lost, because in a chemically
change, atoms are not lost or gained, just
simply rearranged.
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The mass of the stuff that you make in a chemical
reaction is the same as the mass of the stuff that
you start with
ENERGY AND MATTER
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Energy is the ability to do work or cause change.
We use energy to physically and chemically change
matter
The forms of energy that can change matter are:
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Kinetic - molecules move faster when heated
Potential - stored energy in molecules waiting to be
changed
Thermal – heat that changes state of matter (physical).
Heat makes molecules move faster, causing them to bump
into each other and created new molecules(chemical)
Chemical – molecules combine to create new molecules
Electromagnetic – sun provides energy for
photosynthesis, resulting in food (chemical), microwaves
can warm/cook food
Electrical
TODAY’S LAB
Today we will be making pancakes from scratch
so that you may see how matter physically and
chemically changes when energy is added
 We will be doing this cooking show style. I have
premeasured the ingredients
 I will use my griddle under the Ladybug and
project the image
 You will note information on your lab sheet
 This will be an important document for
tomorrow’s assignment
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THE MATTER
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Materials:
1 ½ cups all-purpose
flour
1 ½ cups milk
3 ½ tsp. baking powder
1 egg
1 tsp. salt
3 T. butter, melted
1 T. white sugar
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In a large bowl, sift
together the flour,
baking powder, salt and
sugar. Make a well in
the center and pour in
the milk, egg and
melted butter. Mix until
smooth
Heat a lightly oiled
griddle over medium
high heat. Pour or scoop
the batter onto the
griddle. Brown on both
sides until cooked
through. Serve hot