Matter (7th Grade)

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Matter
Matter
• anything that has mass and takes up
space (volume)
Mass vs. Weight
– Examples:
•
•
•
•
a brick has mass and takes up space
a desk has mass and takes up space
a pencil has mass and takes up space
air has mass and takes up space
All of the above examples are considered matter because
they have mass and take up space. Can you think of anything
that would not be considered matter?
Atoms
-
+
+
+
+
-
-
Taking a closer look will reveal that
atoms are composed of smaller parts
• smallest possible unit into
which matter can be
divided, while still
maintaining its properties
• over 100 different kinds
of atoms exist (≈ 90 occur
naturally
and ≈
25is made
in
For example,
what
the
labs) smallest possible unit
into which
long essay
can be
• cannot
be aseen
by the
divided and still have some meaning?
naked
eye or even an
optical microscope
• can combine, or bond, to
create additional types of
matter
• always moving when above
the temperature of
absolute zero
Atoms are so small that…
•
•
•
•
•
•
it would take a stack of about
50,000 aluminum atoms to equal
the thickness of a sheet of
aluminum foil from your kitchen.
www.deckersfoods.com
if you could enlarge a penny until
it was as wide as the US, each
of its atoms would be only about
3 cm in diameter – about the
size of a ping-pong ball
a human hair is about 1 million
C-C-C-C-C-… + 999,995 more
carbon atoms wide.
a typical human cell contains
roughly 1 trillion atoms.
1 trillion atoms 
a speck of dust might contain
.
3x1012 (3 trillion) atoms.
Is made of approximately 3 trillion atoms
it would take you around 500
years to count the number of
atoms in a grain of salt.
Just one of these grains
Let’s Experiment
In order to try to gain an idea of how
small an atom really is, you will complete
the following activity.
1.
2.
3.
4.
Cut a strip of 11 in. paper in half.
Place one half on the table.
Cut the remaining piece in half.
Continue cutting and placing the
strips on the table as many times as
you can.
5. Make all cuts parallel to the first one.
1st
cut
2nd
cut
3rd
cut
Results
• How many cuts were you able to
make?
• Do you think you could keep cutting
the paper forever? Why or why not?
You would have to cut the paper in
half around thirty-one (31) times to
get to the size of any atom.
http://www.miamisci.org/af/sln/phantom/papercutting.html
Building Molecules/Compounds
• Use the molecular model kit to build and
analyze the following molecules/compounds
O=O
H–O-H
Oxygen Gas
(O2)
Structural Diagrams
Show atomic
Which ofof
arrangement
these are
molecule/compound
Water
(H2O)
molecules?
H
H
H
H
C
C
C
H
H
H
Propane
(C3H8)
H
Chemical Bond
Compounds?
Link holding
atomsBoth?
together
Chemical Symbol
Abbreviation for the
element/atom
OH H OH OH OH
O
C
H
C
C
C
C
C
H OH H
H
H
Glucose
(C6H12O6)
H
Combining Atoms
• There are over one hundred different types of
atoms and they oftentimes combine to make new
substances known as molecules and compounds
Molecule
Compound
Results from the
bonding (covalent) of
two or more atoms
A substance that
contains two or more
different elements
(atoms)
Example – Oxygen Gas (O2)
Example – Water (H2 O)
Compounds are molecules but not all molecules are compounds
Molecule, Compound, or Both?
Comparing Atoms, Molecules,
Compounds, and Elements
Molecule
Atom
What’s
the
matter?
Element
Compound
(or molecule)
Combining Molecules/Compounds
• a combination of two or more substances
that do not combine chemically, but
remain the same individual substances is
known as a mixture
• can be separated by physical means
• two types
• Heterogeneous
• Homogeneous
Based on the prefixes
“hetero” and “homo,”
what do you think are
characteristics of these
two types of mixtures?
Creating Mixtures – Part 1
•
Procedures/Questions
1. Describe and draw what you see in the cups.
2. Pour the contents of cups A and cup B into a
beaker and mix with a glass stirring rod.
3. Describe and draw what you see in the
beaker after cups A and B are combined.
4. Using any means necessary, try to separate
the mixture back into its original parts. Was
it possible to separate the mixture? Why or
why not?
Heterogeneous Mixture
• “hetero” means different
• consists of visibly different substances or
phases (solid, liquid, gas)
• a suspension is a special type of
heterogeneous mixture of larger particles
that eventually settle
• Example:
Trail Mix
Notice the
visibly
different
substances
Creating Mixtures – Part 2
•
Procedures/Questions
1. Describe and draw what you see in the cups.
2. Pour the contents of cups C and cup D into a
beaker and mix with a glass stirring rod.
3. Describe and draw what you see in the
beaker after cups C and D are combined.
4. Using any means necessary, try to separate
the mixture back into its original parts. Was
it possible to separate the mixture? Why or
why not?
Homogeneous Mixture
• “homo” means the same
• has the same uniform appearance and
composition throughout; maintain one
phase (solid, liquid, gas)
• commonly referred to as solutions
• Example:
Salt Water
Notice the
uniform
appearance
Physical Properties of Matter
• any property of matter that can be
observed or measured without changing
the identity of the matter
• Examples
color
shape
taste
state/phase
D=m
density
V
Chemical Properties of Matter
• any property of matter that
describes a substance based on its
ability to change into a new
substance
• Examples
flammability
reactivity with vinegar
reactivity with oxygen
Iron + Oxygen  Iron oxide (rust)
4Fe + 3O2  2Fe2O3
Chemical or Physical Property?
1.
Paper is white
Physical Property
2.
Boiling point of H2O is 100oC
Physical Property
3.
Zinc reacts with hydrochloric acid and creates
hydrogen gas
Chemical Property
4.
Nitrogen does not burn
Chemical Property
5.
Sulfur smells like rotten eggs
Physical Property
Comparing Physical and
Chemical Properties
Substance/Matter
Physical Property
Chemical Property
Helium
Less dense than air
Nonflammable
Hydrogen
Less dense than air
Flammable
Wood
Grainy texture
Flammable
Baking soda
White powder
Reacts with vinegar to
produce bubbles
Powdered sugar
White powder
Does not react with vinegar
Rubbing alcohol
Clear liquid
Flammable
Red food coloring
Red color
Reacts with bleach and loses
color
Iron
Malleable
Reacts with oxygen
Physical Change
• a change in shape, size, color, or state
• a change without a change in chemical
composition
• a change that is reversible
– The Mixtures Lab
• Examples
tearing paper
cutting your hair
change in state
Why do you think Bose-Einstein and
Changes
in States
plasma are not equally distanced from
the other
three states
of matter?
(Physical
Changes)
Plasma
Ionization
Desposition
Recombination
Vaporization
(Evaporation/Boiling)
Liquid
Melting
Solid
Gas
Condensation
Freezing
Sublimation
Bose-Einstein
All changes in state require a
change in energy
Phase Changes Simulation
• PhET
• Harcourt School
• Pearson
This is what happens when energy is added
and/or taken away from matter
Chemical Change
• a change in which a substance becomes another
substance having different properties
• a change that is not reversible using ordinary
physical means
• Changes that usually cause heat, sound, light, odor,
fizzing/foaming, color changes
You usually need more than one of the above
characteristics to be considered a chemical
change!
• Examples
combining sulfuric acid and sugar
burning a piece of wood
soured milk
Chemical or Physical Change?
1.
Bending a Paper Clip
Physical Change
2.
Baking a cake
Chemical Change
3.
The sublimation of carbon dioxide
Physical Change
4.
Crushing an aluminum can
Physical Change
5.
Vinegar and baking soda combining to create salt and
water
Chemical Change
Mass vs. Weight
Mass
•
•
Weight
a measure of how much
matter an object is made of
does not change, regardless
of where something or
someone is
Mass = 59 kg
Weight = 579 N
•
•
the force of gravity on an
object
equal to the mass of the
body times the local
acceleration of gravity
Why do you
Misconception
think the
Alert!
person’s
Does gravity
weight is
always pull
less on the
things down?
moon?
Mass = 59 kg
Weight = 96 N
http://www.exploratorium.edu/ronh/weight/index.html
Element
• a pure substance made up of one kind of
atom
• cannot be broken down or separated into
simpler substances by physical or chemical
means
• Over 100 kinds of elements exist
– 90 occur naturally on Earth
– 25 were made by scientists in labs
http://www.privatehand.com/flash/elements.html
5 Physical States of Matter
• Bose-Einstein
(Newest State)
• Solid
• Liquid
• Gas
• Plasma
Bose-Einstein Condensate
• exist at extremely cold
temperatures (around
absolute zero or -460
oF) which are achieved
by scientists in labs
• particles are super
unexcited
• particles lock or “clump”
together so firmly that
they move as a single
unit
• definite shape and
volume (?)
Solid
• particles are
tightly compact
• particles vibrate
without the ability
to move freely
• definite shape and
volume
• Solid Animation
Liquid
• particles are
tightly compact,
but able to move
around close to
each other
• no definite shape,
but definite
volume
• Liquid Animation
Gas
• particles can easily
spread out or move
close together
• particles move
freely and with a
lot of energy
• no definite shape
or volume
• Gas Simulation
Plasma
•
•
•
•
•
•
exist at extremely high
temperatures (several
million degrees Celsius)
particles are broken apart
particles move freely and
with extremely high energy
this form is not too common
on Earth, however it is the
most common form of
matter in the universe
No definite shape or volume
(?)
Examples: florescent and
neon lights, lightning, aurora
borealis
Why do you think this is the
most common form/state of
matter in the universe?
Energy and the States of Matter
• The physical states of matter result from the
amount of energy the particles composing the
matter have. Basically, more energy means more
movement for the particles and less energy
means less movement.
• Energy/Temperature and Matter Simulations
– PhET
– BEC: Temperature and Absolute Zero
If you were to compare an ice cube and the steam created
from boiling water, which would you think has more energy?
States of Matter Continuum
What about this continuum could
be considered a little misleading?
Taken from: http://www.chem4kids.com/files/matter_becondensate.html
State the Phase
Plasma
B.E.C.
Solid
Liquid
Gas
Layering Liquids
Using a test-tube and the eyedroppers, try to layer the four different
colored liquids so that the colors don’t mix and show distinct layers.
1. Hold the test-tube in your hand at a 45 degree angle.
2. Using the eyedropper from one of the colors, slowly place the
liquid into the test-tube.
3. Repeat step two using the other three liquids until you get them
layered. Record the order of the colors.
If you don’t get clear separation of the colors, you should empty the
contents of the test tube down the drain and start again. These steps
may need to be repeated several times until you discover the correct
order of the colors.
*Placing white paper behind the straws will help you
see the divisions
Layering Liquids - Discussion
1.
Were you capable of layering the four liquids?
If so, what was the correct order from the
bottom up?
2. What difficulties did you experience when
performing this activity?
3. Why do you think the liquids created layers
when putting them in the test tube in the
correct order?
4. Because these liquids are miscible, or partially
miscible, they did not really create distinct
layers. What do you think it means to be
miscible?
Density
• a measure of the amount of matter (mass)
present in a given volume of a substance
• typically expressed in the following units:
– grams per cubic centimeter (g/cm3) for solids
– grams per milliliter (g/ml) for liquids
• does not depend on how much of a substance you
have (intrinsic property) – in other words, the
density of a gold bar would be the same as the
density of a gold flake
• can change as temperature and pressure change
Which do you think
is more dense? Why?
Calculating Density
• Density can be calculated by dividing
the mass of an object by its volume
D=m
V
Sample Problem
Timothy found a solid metal block
that has a mass of 100 grams and
a volume of 25 cm3. What would be
the density of the block?
grams = 4 grams
D = 100
25 cm3
cm3
Practice Problems
1.
Find the density of a substance with a mass of
27 g and a volume of 7 cm3.
D=m
V
2.
D = 27 g
7 cm3
= 3.86 grams
cm3
A block of maple has a mass of 20 grams and a
volume of 26.5 cm3. What is the density of the
block?
D=m
V
D = 20 grams = 0.75 grams
3
3
26.5 cm
cm
The Density Triangle
D
V=m
m = D .V
D
V
m
D
.
V
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