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Introduction to Chemistry
I. Chemistry is the study
of all matter
Matter and it’s Properties
Composition of Matter
Chemistry is “lego-science.” Millions of
legos form very complex structures, but
the basic building block is an individual
lego.
So it also is with matter, all of the complex
structures that we see around us are composed
of basic building blocks. What are these called?
Envision a huge box of legos, all the same
Atoms – The smallest unit of an
color, when we have the same type of
element
that
maintains
the properties
ofonly
Element
–
A
pure
substance
made
of
atoms all grouped together, what do we
that element.
one kind
of atom.
smart
science
types call this?
Elements
•
•
•
•
Gold
Silver
Hydrogen
Oxygen
Most substances on earth are not pure
• Elements combine to form molecules
– Salt (sodium & chlorine)
– Water (hydrogen & oxygen)
– Ozone (2 or 3 oxygen atoms together
Molecules
________________
- two or more atoms
bonded together. Can have the same type of
atoms or different types of atoms.
Matter and it’s Properties
Matter: Mass, Weight and Volume
Matter is the basis of most of what we
see, feel and sense.
matter
MatterWhat
is simply
the ISN’T:
amount of material
(that is atoms/molecules)
a substance
Matter is not thethat
space
that an
is composed
of. takes up. This is the
object
volume of the object.
AllWhile
mattermatter
takes has
up space
volume,
(has
volume is
volume)
NOT matter.
and has mass….
Matter and it’s Properties
Matter: Mass, Weight, and Volume
So to determine the mass of a substance
I simply need to “weigh” it right?
Mass – The measure
of the amount of matter
in a substance.
Mass is constant, it
doesn’t change
depending on your
position.
Weight is a force, it depends on mass AND
gravitational pull or acceleration.
Your weight on other worlds
• http://www.exploratorium.edu/ronh/weight/
What is mass?
• Mass is the amount of
matter in an object
• Mass is constant
• Weight The measure of
the force of gravity on
the mass of an object
• Weight changes with
gravity
Weight formula
• 1 kg = 2.2 pounds
• Weight is mass times gravity
– Gravity (g) =9.8 m/s2 - - round to 10
• Weight= Mass x Gravity
– W= m x g
• Practice:
http://www.gcse.com/eb/gtest.htm
Question 1
The strength of gravity at the Earth’s surface
is 10 Newtons per kilogram. Calculate the
weight of a car with a mass of 1500 kg.
W= M X G
W= 1500kg X 10 N/kg
W= 15000 Newtons
Question 2
The strength of gravity on the moon is 1.6
Newtons per kilogram. If an astronaut’s
mass is 80 kg on Earth, what would the
mass be on the Moon?
80kg because the mass is constant. If the mass is 80
kg on Earth then it will be 80kg on the moon.
• What is the difference between weight and
mass?
– Weight is the measure of gravity on an object’s
mass
COMPARE AND CONTRAST
MASS
vs.
• Amount
• Does not depend on gravity
• Constant
WEIGHT
Depends on gravity
Weight=mass x gravity
Not constant
What about volume?
• If two things weigh the same do they have
the same volumes?
• Can two things with the same mass have
different volumes?
Volume – the amount of space that matter in
an object occupies
Measuring Volume
1. Graduated cylinders can be used to
find the volume of liquids and other
objects.
Read the measurement based on the bottom of the
meniscus or curve. When using a real cylinder, make
sure you are eye-level with the level of the water.
What is the volume of water in the cylinder? _____mL
43
What causes the meniscus?
A concave meniscus occurs when the molecules of the liquid
attract those of the container. The glass attracts the water on
the sides.
the water molecule are attracted to the
glass molecules
Top Image: http://www.tea.state.tx.us/student.assessment/resources/online/2006/grade8/science/images/20graphicaa.gif
Bottom Image: http://morrisonlabs.com/meniscus.htm
What is the volume of water in each cylinder?
37
52
23
Pay attention to the scales for each cylinder.
Images created at http://www.standards.dfes.gov.uk/primaryframework/downloads/SWF/measuring_cylinder.swf
Measuring Liquid Volume
Measuring Solid Volume
9 cm
We can measure the volume of regular object
using the formula length x width x height.
8 cm
_____ X _____ X _____ = _____
We can measure the volume of
irregular object using water displacement.
Amount of H2O with object = ______
About of H2O without object = ______
Difference = Volume = ______
Click here for an online activity about volume.
Choose Lessons  Volume & Displacement
http://resources.edb.gov.hk/~s1sci/R_S1Science/sp/e
n/syllabus/unit14/new/testingmain1.htm
10 cm
5.7 cm
Determine the volume of this cube.
The answer is …
Volume = length x width x height
l = 5.7 cm
w = 5.7 cm
h = 5.7 cm
V = 5.7 cm x 5.7 cm x 5.7 cm
V = 185.19 cm3
• How do you find the volume of a solid
using water displacement?
– Place water in the graduated cylinder, drop in
the solid object, measure the new water level,
subtract
Let’s look back at the questions…
• If two things weigh the same do they have
the same volumes?
What about volume?
• Can two things with the same mass have
different volumes?
Newton’s Laws of Motion
Background
Sir Isaac Newton (1643-1727) an English
scientist and mathematician famous for his
discovery of the law of gravity also
discovered the three laws of motion. He
published them in his book Philosophiae
Naturalis Principia Mathematica
(mathematic principles of natural
philosophy) in 1687. Today these laws are
known as Newton’s Laws of Motion and
describe the motion of all objects on the
scale we experience in our everyday lives.
“If I have ever made any valuable discoveries, it has
been owing more to patient attention, than to any
other talent.”
-Sir Isaac Newton
Newton’s Laws of Motion
1. An object in motion tends to stay
in motion and an object at rest
tends to stay at rest unless acted
upon by an unbalanced force.
2. Force equals mass times
acceleration (F = ma).
3. For every action there is an equal
and opposite reaction.
Newton’s First Law
An object at rest tends to stay at rest
and an object in motion tends to stay
in motion unless acted upon by an
unbalanced force.
Newtons’s
st
1
Law and You
Don’t let this be you. Wear seat belts.
Because of inertia, objects (including you) resist changes
in their motion. When the car going 80 km/hour is stopped
by the brick wall, your body keeps moving at 80 m/hour.
What does this mean?
Basically, an object will “keep doing what it
was doing” unless acted on by an
unbalanced force.
If the object was sitting still, it will remain
stationary. If it was moving at a constant
velocity, it will keep moving.
It takes force to change the motion of an
object.
What is meant by unbalanced
force?
If the forces on an object are equal and opposite, they are said
to be balanced, and the object experiences no change in
motion. If they are not equal and opposite, then the forces are
unbalanced and the motion of the object changes.
Some Examples from Real Life
A soccer ball is sitting at rest. It
takes an unbalanced force of a kick
to change its motion.
Two teams are playing tug of war. They are both
exerting equal force on the rope in opposite
directions. This balanced force results in no
change of motion.
st
1
• Once airborne,
unless acted on
by an
unbalanced force
(gravity and air
– fluid friction),
it would never
stop!
Law
st
1
Law
• Unless acted
upon by an
unbalanced
force, this golf
ball would sit
on the tee
forever.
Newton’s First Law is also called
the Law of Inertia
Inertia: the tendency of an object to
resist changes in its state of motion
The First Law states that all objects
have inertia. The more mass an object
has, the more inertia it has (and the
harder it is to change its motion).
More Examples from Real Life
A powerful locomotive begins to pull a
long line of boxcars that were sitting at
rest. Since the boxcars are so massive,
they have a great deal of inertia and it
takes a large force to change their
motion. Once they are moving, it takes
a large force to stop them.
On your way to school, a bug
flies into your windshield. Since
the bug is so small, it has very
little inertia and exerts a very
small force on your car (so small
that you don’t even feel it).
If objects in motion tend to stay in motion,
why don’t moving objects keep moving
forever?
Things don’t keep moving forever because
there’s almost always an unbalanced force
acting upon it.
A book sliding across a table slows
down and stops because of the force
of friction.
If you throw a ball upwards it will
eventually slow down and fall
because of the force of gravity.
In outer space, away from gravity and any
sources of friction, a rocket ship launched
with a certain speed and direction would
keep going in that same direction and at that
same speed forever.
Newton’s Second Law
The net force of an object is equal to the product of
its mass and acceleration, or F=ma.
Acceleration: a measurement of how quickly an
object is changing speed.
What does F = ma mean?
Force is directly proportional to mass and acceleration.
Imagine a ball of a certain mass moving at a certain
acceleration. This ball has a certain force.
Now imagine we make the ball twice as big (double the
mass) but keep the acceleration constant. F = ma says
that this new ball has twice the force of the old ball.
Now imagine the original ball moving at twice the
original acceleration. F = ma says that the ball will
again have twice the force of the ball at the original
acceleration.
More about F = ma
If you double the mass, you double the force. If you
double the acceleration, you double the force.
What if you double the mass and the acceleration?
(2m)(2a) = 4F
Doubling the mass and the acceleration quadruples the
force.
So . . . what if you decrease the mass by half? How
much force would the object have now?
What does F = ma say?
F = ma basically means that the force of an object
comes from its mass and its acceleration.
Something very massive (high mass)
that’s changing speed very slowly (low
acceleration), like a glacier, can still
have great force.
Something very small (low mass) that’s
changing speed very quickly (high
acceleration), like a bullet, can still
have a great force. Something very
small changing speed very slowly will
have a very weak force.
nd
2
Law
nd
2
Law
The net force of an object is
equal to the product of its mass
and acceleration, or F=ma.
nd
2
Law
• When mass is in kilograms and acceleration
is in m/s/s, the unit of force is in newtons
(N).
• One newton is equal to the force required to
accelerate one kilogram of mass at one
meter/second/second.
nd
2
Law (F = m x a)
• How much force is needed to accelerate a
1400 kilogram car 2 meters per
• Write the formula
• F=mxa
• Fill in given numbers and units
• F = 1400 kg x 2 meters per second
• Solve for the unknown
• 2800 kg-meters/second or 2800
N
nd
2
Law (F = m x a)
What acceleration will result when a 12 N net force
applied to a 3 kg object?
• Write the formula
• F=mxa
• Fill in given numbers and units
• 12N = 3 kg x a meters per second
• Solve for the unknown
• 12N = 3 kg x 4 meters per second
Check Your Understanding
1. What acceleration will result when a 12 N net force applied to a 3 kg object?
12 N = 3 kg x 4 m/s
2. What acceleration will result when a 12N net force applied to a 6 kg object?
12 N = 6 kg x 2 m/s
3. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s2. Determine
the mass.
16 N = 3.2 kg x 5 m/s
If mass remains constant, doubling the acceleration, doubles the force. If force remains
constant, doubling the mass, halves the acceleration.
If mass remains constant, doubling the acceleration, doubles the force. If force remains
constant, doubling the mass, halves the acceleration.
Newton’s 2nd Law proves that different masses
accelerate to the earth at the same rate, but with
different forces.
• We know that objects
with different masses
accelerate to the
ground at the same
rate.
• However, because of
the 2nd Law we know
that they don’t hit the
ground with the same
force.
F = ma
F = ma
98 N = 10 kg x 9.8 m/s/s
9.8 N = 1 kg x 9.8 m/s/s
Newton’s Third Law
For every action there is an equal and
opposite reaction.
What does this mean?
For every force acting on an object, there is an equal
force acting in the opposite direction. Right now,
gravity is pulling you down in your seat, but
Newton’s Third Law says your seat is pushing up
against you with equal force. This is why you are
not moving. There is a balanced force acting on
you– gravity pulling down, your seat pushing up.
Think about it . . .
What happens if you are standing on a
skateboard or a slippery floor and push against
a wall? You slide in the opposite direction
(away from the wall), because you pushed on
the wall but the wall pushed back on you with
equal and opposite force.
Why does it hurt so much when you stub
your toe? When your toe exerts a force on a
rock, the rock exerts an equal force back on
your toe. The harder you hit your toe against
it, the more force the rock exerts back on your
toe (and the more your toe hurts).
Other examples of Newton’s
Third Law
• The baseball forces the
bat to the left (an
action); the bat forces
the ball to the right
(the reaction).
3rd Law
• Consider the motion of
a car on the way to
school. A car is
equipped with wheels
which spin backwards.
As the wheels spin
backwards, they grip
the road and push the
road backwards.
3rd Law
The reaction of a rocket is
an application of the third
law of motion. Various
fuels are burned in the
engine, producing hot
gases.
The hot gases push against
the inside tube of the rocket
and escape out the bottom
of the tube. As the gases
move downward, the rocket
moves in the opposite
direction.
Review
Newton’s First Law:
Objects in motion tend to stay in motion
and objects at rest tend to stay at rest
unless acted upon by an unbalanced force.
Newton’s Second Law:
Force equals mass times acceleration
(F = ma).
Newton’s Third Law:
For every action there is an equal and
opposite reaction.
Inertia:
Vocabulary
the tendency of an object to resist changes
in its state of motion
Acceleration:
•a change in velocity
•a measurement of how quickly an object is
changing speed, direction or both
Velocity:
The rate of change of a position along
a straight line with respect to time
Force:
strength or energy