Matter
***
Matter…
• Makes up all of the objects and living organisms
in the universe
• Anything that has mass AND takes up space
• Light and sound are NOT matter…why?
– Matter is made of particles called atoms…matter IS
atoms.
– Atoms have mass
– Air is made of atoms
– Sound and light waves traveling through air do not
have mass OR take up space
Three (of five) forms of Matter:
• Solid matter - has a fixed volume and shape
of the object or substance.
• Liquid matter - has a definite volume but
not a definite shape.
• Gas matter - does not have a definite shape
and volume.
Mass…
• A physical property of matter
• Measure of how much matter an object contains
• Standard unit: Kilogram (kg)
– 1 kg = 1000 grams (g)
– Ex: grapefruit: 500 g, penny: 2-3 g
• Measure mass using a triple-beam balance
Mass vs Weight
Mass is a measurement of the
amount of matter something
contains
Weight is the measurement of the
pull of gravity on an object.
Mass is measured by using a
balance comparing a known
amount of matter to an unknown
amount of matter.
Weight is measured on a scale.
The Mass of an object doesn't
change when an object's location
changes.
Weight does change with location.
• A triple beam balance compares a known mass to an
unknown mass, so it is unaffected by gravity.
• A scale measures weight, the triple beam balance gives a
true measure of mass.
• On the moon the mass on the left side of the balance may
'exert less force', but then less force will be needed to
balance it.
Weight and Gravity
• Recall…
• Gravity is the force that pulls two masses toward
each other
• Standard unit: Newton (N)
– Common unit: Pound (lb)
• Force = mass * acceleration (F=ma)
– Newton = kilogram*meter/second^2 (N = kg m/s2)
• Weight is a force!
– Mass is amount of matter of an object, weight is how
strongly gravity is pulling on that matter
F = G[M
2
m/r ]
• What will cause the force of attraction to increase
or decrease?
– If either mass increases the force of attraction increases
proportionally. Since the moon has 1/6 the mass of
earth, it would exert a force on an object that is 1/6 that
on earth.
• Why is the 1/r2 factor so important?
– This is an inverse square relationship which seems to show up a lot
in physics. How does it affect the force?
– When r=1 the value 1/r 2 is 1.0, but at r=10 it deceases to 1/100.
That means gravity gets weak 'quick' as we move away from the
earth.
Compute Mass and Weight
• If a cube has a mass of 90.91 kilograms and a
weight of 200 pounds on Earth, what will its mass
and weight be on another planet?
– The Moon has a gravity that is 0.165 of Earth's.
The cube will have a weight of
________________ pounds
and a mass of
_______________ kilograms
– Jupiter has a gravity that is 2.34 times greater than
Earth's…weight? Mass?
Compute Mass and Weight
• On the moon:
– Weight = 33 lb
– Mass = still 90.91 kg!
• On Jupiter
– Weight = 468 lb
– Mass = 90.91 kg
Volume
• Volume is the amount of space an object occupies.
• The volume of an object can be calculated
geometrically using mathematical equations or by
measuring liquid displacement.
• Measure the volume of a cube using the formula
V=(side)x(side)x(side) (length times width times
height) and by using a graduated cylinder to
measure liquid displacement.
• Volume = L x W x H (cm3 or in3 etc.)
• The side of the cube is approximately 3.1 centimeters.
How many inches does this convert to (use 2.54 cm. = 1
inch)?
Measure Volume by Displacement
• What was the amount of water displaced by the
object? (1 ml = 1cm3)
Before
After
Density
• Each box has the same
volume.
• If each ball has the
same mass, which box
would weigh more?
Why?
Density
• The box that has more balls has more mass per
unit of volume. D = m/V
• The density of a material helps to distinguish it
from other materials.
• Mass: grams (g) or kilograms (kg)
• Volume: cubic centimeters (cm3) or cubic meters
(m3)
• Density: grams/cubic centimeter (g/cm3) or
kilograms/cubic meter (kg/m3)
Periodic Table masses:
One gram is about 600,000,000,000,000,000,000,000 amu (a 6 followed by 23
zeros) = 6 x 1023 amu.
Density of a Liquid
• Problem: You are given two unknown liquids. Find the
density of each. Materials: 100ml graduated cylinder,
triple beam balance, calculator, 2 unknown liquids.
• Procedure:
• 1) Find the mass of the empty graduated cylinder.
• 2) Pour unknown liquid #1 into the graduated cylinder to
the 50 ml. level.
• 3) Find the mass of the graduated cylinder with 50ml of
unknown liquid #1.
• 4) Repeat steps 1-3 for unknown liquid #2.
Density of a Liquid
• Liquid #1:
• Given: Mass of empty
graduated cylinder = 78 grams
• Mass of graduated cylinder with
unknown liquid #1= 128 grams.
• Find:
• a) Mass of just the liquid =
____
b) Volume of liquid=_____
c) Density of liquid #1 =____
• Liquid #2:
• Given: Mass of empty
graduated cylinder = 78 grams
• Mass of graduated cylinder with
unknown liquid #2= 117.5
grams.
• Find:
• a) Mass of just the liquid =
____
b) Volume of liquid =_____
c) Density of liquid #2=____
What is the Liquid?
• What is each liquid?
Using the table below
it is now possible for
you to determine what
each liquid is.
• Densities for some
common liquids are:
Substance
Density (gm/cu.cm)
Water
1.00
Cooking oil
0.92
Sea Water
1.025
Carbon tetrachloride
1.58
Benzene
0.87
Glycerin
1.26
Methanol
0.79
Extension: Air Pressure
• Air pressure is the force exerted by the weight of a
column of air above a particular location.
• Imagine a sealed container full of air
• Change the pressure
– Increase the density of the air by either putting
more air molecules into the container or
reducing the volume of the container.
• Therefore, changes in air pressure can come
about by changes in air density
• Atmospheric pressure is defined as the force
per unit area exerted against a surface by
the weight of the air above that surface.
• If the number of air molecules above a surface increases, there are
more molecules to exert a force on that surface and consequently, the
pressure increases.
•The opposite is also true, where a reduction in the number of air
molecules above a surface will result in a decrease in pressure.
Air Pressure & Altitude
• Air pressure decreases as one moves upward through
the atmosphere because the length of the column of
air shortens and hence there is less mass above a
given location.
• Because air is highly
compressible, the air is closely
packed together near the surface
(high density) and less densely
packed aloft