no slide title · 2017-07-27 · states of matter section 1 kinetic theory 〉what makes up matter?...

States of Matter Section 1

Kinetic Theory

〉What makes up matter? 〉According to the kinetic theory of matter,

matter is made of atoms and molecules. These atoms and molecules act like tiny particles that are always in motion.

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Kinetic Theory, continued

• The following are observations of particles in motion.

– The higher the temperature of the substance is, the faster

the particles move.

– At the same temperature, more massive particles move

slower than less massive ones.

• The kinetic theory helps to explain the differences

between the three common states of matter: solid, liquid,

and gas.




States of Matter

〉What is the difference between a solid, a liquid,

and a gas? 〉You can classify matter as a solid, a liquid, or a

gas by determining whether the shape and volume are definite or variable.




States of Matter, continued

• Solids have a definite shape and volume. • Liquids change shape, not volume. • Gases change both shape and volume.

– fluid: a nonsolid state of matter in which the atoms or molecules are free to move past each other, as in a gas or liquid

• Plasma is the most common state of matter.

– plasma: a state of matter that consists of free-moving ions and electrons




Three States of Matter




Energy’s Role

〉What kind of energy do all particles of matter

have?

〉Because they are in motion, all particles of

matter have kinetic energy.

• energy: the capacity to do work




Energy’s Role, continued

• Temperature is a measure of average kinetic energy.

– temperature: a measure of how hot (or cold)

something is; specifically, a measure of the average kinetic energy of the particles in an object

• Thermal energy depends on particle speed and

number of particles.

– thermal energy: the total kinetic energy of a substance’s atoms




Kinetic Energy and States of Matter




Energy and Changes of State

〉What happens when a substance changes from one state of matter to another?

〉The identity of a substance does not change

during a change of state, but the energy of a substance does change.




Changes of State




Energy and Changes of State, continued

• Some changes of state require energy.

• Changes of state that require energy are

melting, evaporation, and sublimation.

– evaporation: the change of state from a liquid to a

gas

– sublimation: the process in which a solid changes

directly into a gas




Energy and Changes of State, continued

• Energy is released in some changes of state.

• Changes of state that release energy are

freezing and condensation.

– condensation: the change of state from a gas to a

liquid




Changes of State for Water




Conservation of Mass and Energy

〉What happens to mass and energy during

physical and chemical changes?

〉Mass and energy are both conserved. Neither

mass nor energy can be created or destroyed.




Conservation of Mass and Energy,

continued

• Mass cannot be created or destroyed.

– In chemical changes, as well as in physical changes,

the total mass of the substances undergoing the change stays the same before and after the change.

– This is the law of conservation of mass.




Conservation of Mass and Energy,

continued

• Energy cannot be created or destroyed.

– Energy may be changed to another form during a

physical or chemical change, but the total amount of energy present before and after the change is the same.

– This is the law of conservation of energy.




Pressure

〉How do fluids exert pressure?

〉Fluids exert pressure evenly in all directions.

– pressure: the amount of force exerted per unit area of a surface

– example: when you pump up a bicycle tire, air particles constantly push against each other and against the tire walls






Pressure, continued

• Pressure can be calculated by dividing force by the

area over which the force is exerted:

• The SI unit for pressure is the pascal.

– pascal: the SI unit of pressure; equal to the force of

1 N exerted over an area of 1 m2 (symbol, Pa)

, or Force F

Pressure PArea A






Buoyant Force

〉What force makes a rubber duck float in a bathtub?

〉All fluids exert an upward buoyant force on matter.

• buoyant force: the upward force that keeps an object

immersed in or floating on a fluid






Buoyant Force, continued

• Archimedes’ principle is used to find buoyant force.

– The buoyant force on an object in a fluid is an upward

force equal to the weight of the fluid that the object

displaces.






Comparing Weight and Buoyant Force






Buoyant Force, continued

• An object will float or sink based on its

density.

– If an object is less dense than the fluid in which it

is placed, it will float.

– If an object is more dense than the fluid in which

it is placed, it will sink.






Density






Pascal’s Principle

〉 What happens when pressure in a fluid changes?

〉 Pascal’s principle states that a change in pressure at any point in an enclosed fluid will be transmitted equally to all parts of the fluid. In other words, if the pressure in a container is increased at any point, the pressure increases at all points by the same amount.

– Mathematically, Pascal’s principle is stated as P1 = P2.

– Because P = F/A, Pascal’s principle can also be expressed as F1/A1 = F2/A2.






Pascal’s Principle, continued

• Hydraulic devices are based on Pascal’s principle.

– Because the pressure is the same on both sides of the enclosed fluid, a small force on the smaller area (left) produces a much larger force on the larger area (right).

– The plunger travels through a larger distance on the side that has the smaller area.






Math Skills

Pascal’s Principle

A hydraulic lift uses Pascal’s principle to lift a 19,000 N car. If the area of the small piston (A1) equals 10.5 cm2 and the area of the large piston (A2) equals 400 cm2, what force needs to be exerted on the small piston to lift the car?

1. List the given and unknown values. Given: F2 = 19,000 N

A1 = 10.5 cm2

A2 = 400 cm2

Unknown: F1






Math Skills, continued

2. Start with Pascal’s principle, and substitute the

equation for pressure. Then, rearrange the equation

to isolate the unknown value.

P1 = P2

1 2

1 2

F F

A A

2 11

2

( )( )F AF

A






3. Insert the known values into the equation,

and solve.

Math Skills, continued

2

1 2

(19,000 N)(10.5 cm )

400 cmF

F1 = 500 N






Fluids in Motion

〉What affects the speed of a fluid in motion?

〉Fluids move faster through small areas than through larger areas, if the overall flow rate remains constant. Fluids also vary in the rate at which they flow.






Fluids in Motion, continued

• Viscosity depends on particle attraction.

– viscosity: the resistance of a gas or liquid to flow

• Fluid pressure decreases as speed increases.

– This is known as Bernoulli’s principle.





12.3 Buoyancy is a force

Buoyancy is a measure of the

upward force a fluid exerts on an

object that is submerged.

The water in the pool

exerts an upward

force that acts in a

direction opposite to

the boy’s weight.

12.3 Volume and buoyancy The strength of the buoyant force on an

object in water depends on the volume of

the object that is underwater.

As you keep pushing downward on the ball, the

buoyant force gets stronger and stronger. Which

ball has more volume underwater?

12.3 Weight and buoyancy

Weight is a force, like any

other pushing or pulling

force, and is caused by

Earth’s gravity.

It is easy to confuse mass

and weight, but they are not

the same.

Weight is the downward

force of gravity acting on

mass.

What is the rock’s

weight?

What is the rock’s

mass?


In the third century BC, a

Greek mathematician named

Archimedes realized that

buoyant force is equal to the

weight of fluid displaced by

an object.

A simple experiment can be

done to measure the buoyant

force on a rock with a spring

scale when it is immersed in

water.

12.3 Weight and buoyancy In air the buoyant

force on the rock is

29.4 N.

When the rock was

submerged, the scale

read 19.6 N.

The difference is a

force of 9.8 N, exactly

the amount of force

the displaced water

exerts.


These blocks are the same total volume.

Which block has more buoyant force acting on it?

Which block weighs more in air?


Buoyancy

explains why

some objects sink

and others float.

Whether an object

sinks or floats

depends on how

the buoyant force

compares with

the weight.

12.3 Density and buoyancy

If you know an object’s density you

can quickly predict whether it will

sink or float.

Which ball will sink in water?

Which ball will float in water?


Average density helps determine

whether objects sink or float.

An object with an average density

GREATER than the density of water will

sink.

An object with an average density LESS

than the density of water will float.


What can you say about the

average density of these blocks?


When they are completely underwater,

both balls have the same buoyant

force because they displace the same

volume of water.

12.3 Boats and average density

Use your understanding of average

density to explain how steel boats

can be made to float.

12.3 Boats and average density If you have seen a loaded cargo ship, you

might have noticed that it sat lower in the

water than an unloaded ship nearby.

This means a full ship must displace more

water (sink deeper) to make the buoyant

force large enough to balance the ship’s

weight.

12.2 Properties of Fluids

A fluid is defined

as any matter that

flows when force

is applied.

Liquids like water

or silver are kinds

of fluid.

12.2 Pressure

A force applied to a fluid creates

pressure.

Pressure acts in all directions, not

just the direction of the applied

force.

12.2 Forces in fluids

Forces in fluids are more complicated

than forces in solids because fluids

can change shape.

12.2 Units of pressure

The units of

pressure are force

divided by area.

One psi is one

pound per square

inch.


The S.I. unit of

force is the pascal.

One pascal (unit

of force) is one

newton of force

per square meter

of area (N/m2).

12.2 Pressure

If your car tires are

inflated to 35 pounds

per square inch (35

psi), then a force of 35

pounds acts on every

square inch of area

inside the tire.

What might happen if you over-inflate a tire?

12.2 Pressure On the microscopic

level, pressure comes

from collisions

between atoms.

Every surface can

experience a force

from the constant

impact of trillions of

atoms.

This force is what we

measure as pressure.

12.2 Pressure

In a car engine high pressure is created by

an exploding gasoline-air mixture.

12.2 Energy conservation and Bernoulli’s Principle

Streamlines are

imaginary lines drawn

to show the flow of

fluid.

Bernoulli’s principle

tells us that the energy

of any sample of fluid

moving along a

streamline is constant.

12.2 Bernoulli’s Principle

Bernoulli’s principle says the three

variables of height, pressure, and

speed are related by energy

conservation.

12.2 Three Variables and Bernoulli’s Principle

If one variable increases along a streamline,

at least one of the other two must decrease.

For example, if speed goes up, pressure

goes down.

12.2 The air foil

One of the most important

applications of Bernoulli’s

principle is the airfoil

shape of wings on a plane.

When a plane is moving,

the pressure on the top

surface of the wings is

lower than the pressure

beneath the wings.

12.2 Viscosity

Viscosity is the property of fluids that

causes friction.

Viscosity is determined in large part

by the shape and size of the particles

in a liquid.

12.2 Viscosity and temperature

As the temperature of a

liquid increases, the

viscosity of a liquid

decreases.

Increasing the kinetic

energy of the substance

allows the particles to

slide past one another

more easily.

13.1 What’s in Earth’s atmosphere?

Nitrogen (N2) gas

makes up about 78

percent of Earth’s

atmosphere.

Nitrogen is

released into the

air by volcanoes

and decaying

organisms and is a

vital element for

living things.

13.1 Comparing atmospheres

An atmosphere is a layer of gases

surrounding a planet or other body in space.

13.1 Life changed Earth’s atmosphere

Over time,

photosynthesis

breaks down

carbon dioxide,

uses carbon to

build the organism,

and releases

oxygen into the air.

13.1 Atmospheric pressure

Atmospheric pressure is

a measurement of the

force of air molecules in

the atmosphere at a

given altitude.

Your ear drum is one

way you can detect

changes in pressure.

13.1 Pressure in the atmosphere

At sea level, the weight of

the column of air above a

person is about 9,800

newtons (2,200 pounds)!

This is equal to the

weight of a small car.

Why aren’t we crushed by

this pressure?

13.1 Measuring Pressure

A barometer is an

instrument that

measures

atmospheric

pressure.

Mercury barometers

were common until

we discovered their

vapors were harmful.

13.1 Measuring Pressure

Today we use

aneroid barometers.

They have an airtight

cylinder made of thin

metal.

The walls of the

cylinder respond to

changes in pressure.

13.1 Pressure in the atmosphere

The gas molecules

closest to Earth’s

surface are packed

together very

closely.

This means

pressure is lower

the higher up you

go into the

atmosphere.

no slide title · 2017-07-27 · states of matter section 1 kinetic theory 〉what makes up matter?...

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