Section2 - Weebly

Section 2.3

The Kinetic Theory

(pg. 476-‐480)

OBJECTIVES:

•  Explain the kinetic theory of matter

•  Describe particle movement in the 4 states of

matter.

•  Explain particle behavior at the melting and

boiling points.

Vocabulary:

•  Kinetic theory •  Melting point

•  Boiling point

•  Solid

•  Liquid

•  gas

•  Plasma

•  diffusion

What states of matter are present?

•  SOLID: veggies, pot,

•  LIQUID: soup itself

• GAS: steam off soup

Kinetic Theory:

• An explanation of how

particles in matter behave.

Kinetic Theory’s Explanation: 1.  All matter is composed of small

particles (atoms, molecules, and ions).

2.  These particles are in constant, random

motion.

3.  These particles are colliding with each

other and the walls of their container.

Picture it….

Keep in mind….

•  As atoms are bumping into each other they

are transferring energy.

•  The more energy they have, the faster they

move, the faster they bump into others

•  Increasing the temp of a material increases

the movement of its atoms.

• Take out a sheet of paper please…..

•  Fold a sheet of paper in half lengthwise.

Make the back edge about 5 cm longer

than the front edge.

•  Turn the paper so the fold is on the

bottom. Then fold it into thirds.

• Unfold and cut only the top layer

along both folds to make three tabs.

Label the Foldable as shown.

SOLIDS

Characteristics of a SOLID

• Has a definite shape all its own

•  Can be weighed in grams

•  Can be counted

• Molecules are tightly packed

together-‐ can’t escape

LIQUIDS

Characteristics of LIQUIDS •  No definite shape

•  Does have a definite volume

•  Can measure volume

•  Can flow

•  Particles are moving freely enough to

slip out of ordered arrangement

Characteristics of GASES •  No definite shape

•  No definite volume

•  Can flow

•  Particles are moving fast enough to

escape the attractive forces between

them

2 ways a liquid can become a gas:

• Evaporation

• boiling

Evaporation

• The vaporization of a liquid

that happens at the

SURFACE of the liquid.

Boiling point:

• The temperature at which a

liquid will enter the gaseous state

– happens throughout the

ENTIRE liquid

The movement of particles and the

collisions between them cause gases to diffuse.

Diffusion: • The spreading of particles throughout a given volume

until they are uniformly

distributed.

• Diffusion happens MOST

RAPIDLY in gases, but can

happen in liquids too.

PLASMA

PLASMA:

•  Matter consisting of positively and

negatively charged particles.

•  The overall charge of plasma is neutral

bc equal #’s of both charges are present.

Plasma

Characteristics of PLASMA • Most common state of matter in the

UNIVERSE.

•  Very similar to the movement of gas

molecules, only faster.

Common examples of plasma:

Lightning

Bolts


Neon

signs


Fluorescent

tubes


stars


auroras

RECALL: • Particles move faster and

separate as the temperature

rises.

• When the temp of an object is

lowered, the particles slow down.

• The separation of the particles results in an expansion of the

entire object, known as

thermal expansion.

THERMAL EXPANSION:

• An increase in the size of a substance when the

temperature is increased.

The opposite is true too….

•  Temp decreases, particles slow down

•  Attraction bow particles increases,

pulling particles closer together

•  Results in an overall shrinking of the substance, known as contraction.

Expansion joints in sidewalk

Strange behavior of water: • Water is an exception to the thermal

expansion rule:

– Temp increase, size increase

– Temp decrease, size decrease

•  Water molecules have high negatively and

positively charged areas.

•  As the temp of water decreases, particles

move closer together.

•  The unlike charges will be attracted to each

other and line up so that only positive and

negative zones are near each other.

•  This causes empty spaces to form in the

structure.

•  These empty spaces are larger in ice than in

liquid water, so water expands when going

from a liquid to a solid state

•  Solid ice is less dense than liquid

•  Causes ice to float

PROPERTIES OF FLUIDS Section 2.4: (pg. 485-‐489)

Objectives

•  Explain Archimedes’ principle

•  Explain Pascal’s principle

•  Explain Bernoulli’s principle and explain how

we use it.

Vocabulary:

Buoyancy pressure viscosity

Why do ships float?

Why do ships float? •  They float because a greater force is

pushing up on the ship than the

force of the ship pushing down.

•  This supporting force is called the buoyant force.

Buoyancy:

• The ability of a fluid-‐ a liquid or a gas-‐ to exert an upward

force on an object immersed

in it.

Archimedes' principle

Archimedes’ Principle •  If the buoyant force is equal to the

object’s weight, the object will float.

•  If the buoyant force is less than the object’s weight, the object will sink.

Remember:

• Density (D) = Mass (M)

Volume (V)

Density of water = 1 g/ml

Density • An object will float if its density is

less than the density of the fluid

it is placed in.

•  The density of the steel block is greater than the density of water, so it sinks.

•  The density of the wood block is less

than the density of water, so it floats.

Difference in mass

Wood block

•  D = 5 gram /10 cm

•  D = 0.5 g/cm

•  Object floats

Steel block

•  D = 20 gram / 10 cm

•  D = 2 g/cm

•  Object sinks

Difference in volume

Wood block

•  D = 20 gram /30 cm

•  D = 0.67 g/cm

•  Object floats

Steel block

•  D = 20 gram / 10 cm

•  D = 2 g/cm

•  Object sinks

Mass and Volume affect Density •  If you formed that same steel block into the

shape of a hull filled with air, the same mass

would take up a larger volume.

•  The overall density of the steel boat and air

would be less than the density of water

•  The steel (boat) would now float

Mass and Volume affect Density

•  The steel (boat) would now float.

Pascal’s Principle •  Blaise Pascal (1692-‐1662), a French scientist discovered a useful property of

fluids.

Liquids AND Gases are considered to be

fluids because they both have the ability to

flow.

Pascal’s Principle

•  According to Pascal’s Principle, pressure applied to a fluid is transmitted throughout

the entire fluid.

•  http://www.youtube.com/watch?

v=epOwdGIDzlY

Example of Pascal’s principle •  For example when you

squeeze one end of a

toothpaste tube,

toothpaste emerges from

the other end. The

pressure has been

transmitted through the

fluid toothpaste

Pressure:

• Force exerted per unit area.

• P= F / A

Applying the principle • Hydraulic machines are machines

that move heavy loads in accordance

with Pascal’s principle.

•  (Ex: hydraulic lift in auto repair shops)

Hydraulic lift

1. A pipe filled

with fluid

connects small

and large

cylinders.

Applying the principle 2. Pressure applied

to the small

cylinder is

transferred

through the fluid

to the large

cylinder.

Bernoulli’s Principle

• According to Bernoulli’s principle,

as the velocity of a fluid

increases, the pressure exerted

by the fluid decreases.

Bernoulli’s Principle •  The velocity of the air you blew over the

top surface of the

paper is greater than

that of the quiet air

below it.

Bernoulli’s Principle •  As a result, the air pressure pushing

down on the top of

the paper is lower

than the air pressure

pushing up on the

paper.


•  The net force below the paper

pushes the paper

upward.

Video Clips 16

Fun examples of Bernoulli’s Principle

•  http://www.youtube.com/watch?v=P-‐

xNXrELCmU

Fluid Flow

•  Another property exhibited by fluid is its tendency to flow.

•  Fluids vary in viscosity: warm syrup

would flow faster when spilled than cold

syrup

•  Viscosity: Resistance of liquid to flow.

Copyright © 2010 Ryan P. Murphy

High Viscosity = travels slow because of high resistance

High viscosity = flows slowly

Low viscosity= flows fast bc of low resistance

Low viscosity = flows quickly

•  Activity! What is more viscous?

– Remember, Viscosity is resistance to flow.


Which is more viscous?

•  Answer! The peanut butter doesn’t flow as

much as the ketchup so it has more viscosity.


Review Question:

•  If the buoyant force on an object in a fluid is LESS than the object’s weight, the object will

________.

A.  Float

B.  Sink

Answer:

•  If the buoyant force on an object in a fluid is LESS than the object’s weight, the object will

________.

A.  Float

Review Question:

•  According to Pascal’s principle, __________ applied to a fluid is transmitted throughout the

fluid.

A.  Density B.  Pressure C.  Temp D.  volume

Answer:

•  According to Pascal’s principle, __________ applied to a fluid is transmitted throughout the

fluid.

A.  Density B.  Pressure C.  Temp D.  volume

Review Question

•  The more viscous a fluid is the

______________ it will flow?

•  Faster •  Slower •  Farther • Heavier

Answer:

The more viscous a fluid is the

______________ it will flow?

•  Faster

•  Farther • Heavier

BEHAVIOR OF GASES Section 2.5 (pg. 490-‐495)

Remember:

•  Kinetic theory tells us that all gas particles are constantly moving and

colliding with anything in their path.

•  The collision of these particles in the air result in pressure.

Pressure:

•  Force exerted per unit area

•  P = F / A

Gases are often confined to containers.

They remain

inflated bc of

collisions the air

particles have

with the walls of

the container

(balloon)

•  The air molecules hitting the walls of

the balloon cause the walls to

expand outward.

•  If more air is pumped into the

balloon, the # of air molecules is

increased.

This causes

more collisions

with the walls

of the

container

causing it to

expand.

Since the walls

of the bicycle

tube can’t

expand very

much, the

pressure within

the tube would

increase.

•  Pressure is measured in a unit called Pascal

(Pa), the SI unit of pressure.

•  Most pressures are expressed as kPa or 1,000

Pascals (sometimes called atm – atomic

pressure)

•  The pressure of a gas depends on how often

its particles strike the walls of the container.

•  If you squeeze gas into a smaller space, its

particles will strike the walls more often –

giving an increased pressure.

– The opposite is true too

•  If you give the gas particles more space, they

will hit the walls less often – gas pressure is

reduced.

•  British scientist named Robert Boyle

described this property of gases….

Boyle’s Law Pressure-‐Volume Relationship

•  The pressure and volume of a sample of

gas at constant temperature are

inversely proportional to each other.

Boyle’s Law

•  (as one goes up, the other goes down)

•  P goes up, V goes up: P goes down, V goes

down

•  P1V1 = P2V2

•  If 3 of the variables are known, the fourth can

be calculated.

Work it out •  The gas in a 20.0 mL container has a

pressure of 2.77 kPa. When the gas is

transferred to a 34.0 mL container at the

same temperature, what is the new pressure

of the gas?

• P 1V 1 = P2V2

Work it out •  The gas in a 20.0 mL container has a

pressure of 2.77 kPa. When the gas is

transferred to a 34.0 mL container at the

same temperature, what is the new pressure

of the gas?

ANSWER: 1.63 kPa

•  If a set amount of gas is transferred

into a larger container, would the

pressure go up or down?

•  If a set amount of gas is transferred

into a larger container, would the

pressure go up or down?

Answer: DOWN

• Would there be more collisions, or

fewer collisions with the container

holding the gas if the gas was

transferred into a larger container?

• Would there be more collisions, or

fewer collisions with the container

holding the gas if the gas was

transferred into a larger container?

Answer: FEWER

Rationale: •  The more volume (space) means fewer

collisions with the container, therefore

pressure goes down.

(from 2.77 kPa to 1.63 kPa)

Boyle’s Law in Action


v=27yqJ9vJ5kQ

Charles’s Law

Temperature-‐Volume relationship

•  At constant pressure, the volume of a

fixed amount of gas is directly

proportional to its absolute

temperature.

•  As Temp goes up, V goes up

•  As Temp goes down, V goes down

V1 V2

______ = _________

T1 T2

If 3 of the variables are known, the fourth can be calculated

Work it out: • What will be the volume of a gas

sample at 355K if its volume at 273K

is 8.5 L?

Work it out: • What will be the volume of a gas

sample at 355K if its volume at 273K

is 8.5 L?

ANSWER: 11.1 L

•  If the temperature of a given

quantity of gas is increased, what

will happen to the volume it

occupies? (In an elastic container?)

•  If the temperature of a given quantity of gas is

increased, what will happen to the volume it

occupies? (In an elastic container?)

ANSWER: volume would increase (container

would get bigger)

Rationale:

• Gas particles moving faster would

have more collisions with the

container and exert more force to

enlarge the volume of the elastic

container.

Fun with Charles’s Law

•  http://www.youtube.com/watch?v=Jeso

•  E4F2Pb20


v=GcCmalmLTiU

Review Question •  Boyle’s Law states that as the pressure

exerted on a container of gas increases, the

volume of the gas will _____.

A.  Increase B. decrease

C. Stay the same D. none of the above

ANSWER: •  Boyle’s Law states that as the pressure

exerted on a container of gas increases, the

volume of the gas will _____.

A.  Increase B.

C. Stay the same D. none of the above

REVIEW QUESTION:

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