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Transcript of STATES OF MATTER - Wikispaces · PDF fileof any substance to stop moving ... occupies LESS...
Kinetic Theory of Matter • Matter is made up of particles
which are in continual random
motion
Misconception: Only when a substance is in its liquid or gas state do its particles move because in these two states the substance is fluid (it flows).
Truth: in order for the molecules of any substance to stop moving completely, the substance would have to be frozen to absolute zero, a temperature unattainable in nature.
• Particles of solids are
tightly packed, vibrating
about a fixed position.
• Solids have a definite
shape and a definite
volume.
• Sometimes the
arrangement of
particles is regular and
geometric and crystals
are formed and
sometimes the material
is amorphous.
Which ones in each set below have more
population density and why?
Set A
Set B
Which one is more dense?
The one on the right has
more density. MORE
people, same space.
They both have
the same density.
MORE people in
the second one
but MORE space
as well
Which one is
more dense –
Item A or Item
B - and why?
Item B Item A
Ans. Item B is
more dense. It
occupies LESS
space but has the
SAME mass as
Item A. That’s
why the scale is
balanced.
Which one is more dense and why? Which one is more dense and why?
Item B
Item A
Ans. Here
we can’t
tell. Item A
has MORE
mass, but
also
occupies
MORE
space.
• The density of a substance
is the mass per unit
volume it has, in other
words, how compact the
substance is. The formula
for density is:
volume
massdensi ty
units _gm_
cm3
What is density?
Elasticity Some objects stretch
and return to their
original shape.
These objects are
elastic. Objects that
don’t return to their
original shape are
inelastic.
The amount of stretch (x) of an
elastic object is directly proportional
to the force (F) that stretches it. This
is called Hooke’s Law:
Elastic Inelastic
10 kg
20 kg
40 kg
2 cm
4 cm
8 cm
F x
Elasticity Example
100 N
? cm 45 cm
45cmx20N100x2
900100x2
cm9x2
20 N
A certain spring stretches
45 cm when a weight of
100 N is suspended from it.
How much will it stretch if a
force of 20 N is suspended
from it?
F x
2
2
1
1
x
F
x
F
2x
N20
cm45
N100
Scaling
2 units long
x 2 units wide
x 6 sides_____
S. Area: 24 un2
The SURFACE AREA and VOLUME of a cube (2 units on a side) are shown:
Suppose we double the linear dimensions (length, width, and height). What
happens to the SURFACE AREA and the VOLUME of our cube?
2 units long
2 units wide
x 2 units deep__
Volume: 8 un3
4 units long
x 4 units wide
x 6 sides_____
S. Area: 96 un2
4 units long
4 units wide
x 4 units deep__
Volume: 64 un3
DOUBLING (x2) the linear dimensions results
in QUADRUPLING (x4) the surface area and
OCTUPLING (x8) the volume
Find the mass of the following objects:
Densities of some common materials
Density Density
Material (in gm/cm3) Material (in gm/cm3)
Osmium 22.6 Steel 7.8
Gold 19.3 Ice 0.92
Lead 11.3 Water at 4°C 1.00
Gold Lead
Ice
5 cm 2.5 cm 3 cm
5 cm
Volume = l x w x h Volume = r2h Volume = 4/3 r3
Liquids have an
indefinite shape and
a definite volume.
Particles of liquids
are tightly packed,
but are far enough
apart to slide over
one another.
• Which layer has
the highest
density?
• Which layer has
the lowest density?
• Which is fresh
water, oil, salt
water, alcohol?
Liquid Layers
Where is the pressure greater?
5 m
10 m
EVIDENCE: If
one were to
make a hole in
the side of each
container, the
water would
squirt out much
further out of the
bottom one…
The volume of the water
displaced equals the
volume of the irregularly
shaped object.
How do you find the volume of an
irregularly (non-geometrically) shaped
object?
Where does bouyancy come from? In other
words, why do objects feel lighter underwater?
Bouyant Force
There is a
pressure
difference
between
the top and
the bottom
of the
object
which are
at different
depths.
Archimedes’ Principle An immersed object is buoyed
up by a force equal to the
weight of the fluid it displaces 5
3
0.0 N 2.0 N
0 N
3 N + 2 N = 5 N
Apparent
weight of
rock
Weight of
water
displaced
Total Weight
of Object in
air
Pascal’s Principle Changes in pressure at any point in an enclosed
fluid at rest are transmitted undiminished to all
points in the fluid and act in all directions
(because fluids are uncompressible)
Pascal’s Principle If the pistons have different areas, then the pressure
(force per unit area) will be the same. This allows
heavy loads to be lifted (LARGE FORCE). However,
they will be lifted over a small distance.
d
d
Principle of Flotation
A floating object displaces a weight of fluid equal
to its own weight.
0 N 0 N
5 N 5 N
The trick to get
something more
dense than water to
float is to shape it so
that it displaces as
much water as its
own weight.
REMEMBER: the bouyant force is determined
by the volume of water displaced, not by the
weight of the object.
That’s why the same one ton piece of iron (see
below) sinks when shaped like a block but floats
when molded into a bowl shape
Fw Fw
FB FB
A 1-kg rock weighs 9.8 N. The water in the container
below also weighs 9.8 N. When submerged underwater,
the rock’s apparent weight is 7.8 N.
B. If the container of water on the
scale weighs 9.8 N, what is the
0 N
? N 0 N
9.8 N
0 N
? N
9.8 N
7.8 N
A. What is the bouyant force on the rock?
scale reading when
the rock is suspended
beneath the surface
of the water?
C. What is the scale
reading when the
rock is resting on
the bottom of the
container?
Gases have an
indefinite shape
and an indefinite
volume.
Particles of gases
are very far apart
and move freely.
• pressure with incr. depth.
•Same density throughout.
• Temperature with incr.
depth.
• pressure with incr. depth.
• density at bottom.
•Temperature with incr.
depth.
Both liquids and gases are fluids, and basically obey
the same principles, but there are some differences...
Ocean of Air Ocean of Water
The weight of air upon one-square
meter of ground at sea level is
about 100,000 N (10,200 kg).
So atmospheric pressure is about:
100,000 Newtons per square
meter or
100,000 N/m2 or
100,000 Pascals or
100 kPa
In order to keep
the cabin
pressurized at
all altitudes, a
commercial
airliner like a
747 carries up
to 1000 kg of
additional air in
tanks.
WATER PUMP. When you push down
the crank, it sucks the air out of the
chamber with a piston allowing air
pressure to push down on the water
in a well through one tube and
making it rise to the surface through
the other tube.
Vacuum
created here
Air pressure pushing
on well water
Wate
r risin
g to
the s
urfa
ce
The varying pressure of the air on a dish of mercury
can produce a measuring device called a barometer.
Normal Atmospheric
Pressure Lower Atmospheric
Pressure
76 cm
Why is mercury, a toxic substance, used and not
water, for example, in a barometer.
Because of its high
density, mercury only
rises 0.76 m due to
atmospheric pressure.
A column of water
(lower density) in a
barometer would be
10.3 m high
10.3 m
Boyle’s Law P1V1 = P2V2
The product
of the
pressure
and volume
for a given
mass of gas
stays the
same as
long as the
temperature
doesn’t
change.
P1 and V1 are the original pressure and
volume and P2 and V2 are the final
pressure and volume
Bouyancy in Air
Any object that has a
mass less than the mass
of an equal volume of
surrounding air will rise.
In other words, objects
that are less dense than
the air around it will rise.
Bernoulli’s Principle
We are talking about the pressure IN
the fluid not the pressure on things the
fluid ACTS on.
When the speed of a fluid
increases, the pressure drops.
The air travels faster on the upper side
of the wing meaning there is less
pressure on the upper side than the
lower side so the wing rises.
Bernoulli’s Principle explains
why the wings of an airplane
have LIFT and the plane can fly.
LIFT
Bernoulli’s Principle
1.This room (H9) has dimensions of 6 meters
(wide) by 8 meters (long).
A.What is the weight of the air on the
floor?
B. What is the air pressure on the floor?
2.Squeeze a balloon to a third of its volume,
by how much will the pressure inside the
balloon increase? Double the pressure on
the balloon, by how much will its volume
decrease?
3.A scuba diver 10.3 m below the surface of
the water breathes compressed air into her
lungs. If she holds her breath while
retuning to the surface, by how much will
the volume of her lung’s increase?
PHASE CHANGES Description of
Phase Change
Term for Phase
Change
Heat Movement During
Phase Change
Solid to
liquid
Melting
Heat goes into
the solid as it
melts.
Liquid to
solid Freezing
Heat leaves the
liquid as it
freezes.
PHASE CHANGES Description of
Phase Change
Term for Phase
Change
Heat Movement During
Phase Change
Liquid to
gas
Vaporization,
which includes
boiling and
evaporation
Heat goes into the
liquid as it vaporizes.
Gas to liquid Condensation Heat leaves the gas
as it condenses.
Solid to gas Sublimation Heat goes into the
solid as it sublimates.
B. Phase Properties
Phase
Particle Properties
Proximity Energy Motion Volume Shape
Solid
Liquid
Gas
close little vibrational definite definite
close moderate rotational definite indefinite
far apart a lot translational indefinite indefinite
B u t w h a t h a p p e n s i f y o u r a i s e t h e t e m p e r a t u r e t o s u p e r -h ig h le v e l s …
b e tw e e n 1 000°C a n d 1 ,000,000,000°C ?
W i l l e v e r y t h in g ju s t b e a g a s ?
STATES OF MATTER
PLASMA A plasma is an
ionized gas.
A plasma is a very
good conductor of
electricity and is
affected by
magnetic fields.
Plasmas, like gases
have an indefinite
shape and an
indefinite volume.
• Plasma is the
common state
of matter
STATES OF MATTER
SOLID LIQUID GAS PLASMA
Tightly packed, in
a regular pattern
Vibrate, but do not
move from place
to place
Close together
with no regular
arrangement.
Vibrate, move
about, and slide
past each other
Well separated
with no regular
arrangement.
Vibrate and move
freely at high
speeds
Has no definite
volume or shape
and is composed
of electrical
charged particles