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.

The Four States of Matter

Solid Liquid Gas Plasma

• 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.

…the Bouyant

Force is greater

than the weight

of the object Fw

An object will float

when …

An object will float

when …

…the Bouyant

Force is greater

than the weight

of the object Fw

An object will float

when …

…the Bouyant

Force is greater

than the weight

of the object

Fw

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

At sea level, one cubic meter of air at

20°C, has a mass of about 1.2 kg.

1 m3

of air 1.2 kg

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

S o m e p la c e s w h e r e p la s m a s a r e fo u n d …

1. Flames

2. Lightning

3. Aurora (Northern Lights)

T h e S u n is a n e x a m p le o f a s t a r in i t s p la s m a s ta t e

COLD PLASMA

COLD PLASMA PEN