Test 2 Review

Chapters 11 -20

Chapter 11 – Atomic Nature of Matter

• Summary of Terms

– Atom

– Brownian Motion

– Atomic Nucleus

– Electron

– Proton

– Neutron

– Atomic Number

– Atomic Mass Unit (AMU)

– Isotopes

– Periodic table

– Compound

– Molecule

– Chemical reaction

– Mixture

– Quantum Mechanics

– Antimatter

– Dark Matter

Atoms Are Composite Objects

• Protons (+ electric charge), p• Electrons (– electric charge), e• Neutrons (no charge), n• Proton and Neutron have about the same mass• Electron is about 2000 times less massive than proton• Electrical Forces produce attraction between electrons and the

protons in the nucleus (they are oppositely charged)

Cloud of “electron probability”

Chemical elements are defined by the number of protons in the atom’s nucleus

• Hydrogen: 1 proton & 1 electron

proton

10-10 m

Carbon has 6 protons

Nucleus:6 protons

6 or 7 neutrons

Cloud of 6 electrons

Elements in columns (groups) have similar outer-electron configurations,

and so tend to behave similarly.

The Periodic Tablea

lkal

is

alkali earths

rare earths

halogens

noble gases

transition metals

actinides

Structure of the Atom

Chapter 12 - Solids

• Summary of Terms– Atomic binding– Density– Elasticity– Hooke’s law– Scaling

Density

• Mass Density = Mass/Volume

• Weight Density = Weight/Volume

• Units are Kg/m3

• Water density is 1000 Kg/m3 or 1 g/cm3

Chapter 13 - Liquids

• Summary of Terms– Pressure– Buoyant force– Archimedes principle– Principle of floatation– Pascal’s principle– Surface tension– Capillarity

Pressure

• Pressure = force / area• Standard International (SI) units are Pascals• 1N/m2 = 1 Pa about pressure of dollar bill on a table.• Liquid pressure = weight density x depth

– Independent of volume!!!• For fresh water density is 1000 kg/m3

• For water, weight density is 1000*9.8 = 9800N/m3

• (liquid density is almost constant – Liquids are almost incompressible!)

Archimedes’ Principle

• An immersed body is buoyed up by a force equal to the weight of the fluid it displaces.

– True for Liquids and Gases– Objects weigh more in air than in liquid!– If an object is denser than fluid, it will sink.– If an object is less dense it will float.– If an object has equal density it will neither float or sink – like a

fish.– If a 25 kg object displaces 20 kg fluid, it’s apparent weight is 5 kg

Pascal’s Principle

• A change in pressure at any point in an enclosed fluid at rest is transmitted undiminished to all points in the fluid.

Surface Tension & Capillary Action

• Liquid surfaces tend to contract and force each drop into shape having least surface area.

• On the space shuttle, water drops are spherical!• Attraction of unlike surfaces is called Adhesion, like water in thin

glass tubes. Molecules act as sticky balls on the glass.• Attraction of like surfaces is cohesion.

Chapter 14 – Gases and Plasmas

• Summary of Terms– Atmospheric pressure– Barometer– Boyle’s law– Archimedes principle for air– Bernoulli’s principle– Plasma

Atmosphere

• Dry air at 20o C has a density of 1.21 kg/m3 which is about 2 ¾ lbs.

• Barometers measure air pressure– Need 10.3 meters of water in a pipe to balance atmosphere

(depends on atmospheric pressure).– Turn long pipe of water into a bucket of water and water level in

pipe will be 10.3 M with vacuum above water in pipe.

Boyle’s Law

P1V1 = P2V2

• Holds for constant temperature• Pressure is proportional to density – when volume is decreased,

density and pressure increase• Double pressure by decreasing volume by half

Archimedes’ Principle – Again!

• An immersed body is buoyed up by a force equal to the weight of

the fluid it displaces. – Is valid for gasses as well as liquids!– Objects weigh more in a vacuum than in air!

Bernoulli’s Principle

Water speeds up in narrower pipes!Where Speed of fluid increases, pressure in fluid decreasesHolds for Laminar air flow (smooth flow, not turbulent).

Plasma – the Fourth State of Matter

• Solid Liquid Gas Plasma

Increasing Temperature

Plasmas are generally greater than 10,000 degrees

Plasma – the Fourth State of Matter

• A plasma is an ionized gas that responds to electric and magnetic fields.

• The visible universe is made of 99% plasma.• The sun is a giant ball of plasma• High temperature Plasma must be contained in magnetic bottles. If

the plasma were to come into contact with a physical container, it would vaporize the container.

• Lightning is a plasma• Fusion power research uses a plasma at ~ 10M oC

Chapter 15 – Temperature, Heat and Expansion

• Summary of Terms– Temperature– Absolute zero– Heat– Internal energy– Specific heat capacity

Temperature ScalesThe Celsius Scale

• How does one create a scale?– It comes from experiment

Mercury, let’s say

observed level of mercury whenplaced in freezing pure water, callthis 0oC

level of mercury when placed inboiling water -call this 100 OC

Divide thisdistance into100 evenparts =1 oC intervalson the Celsius “scale”

Kelvin Scale

• The theoretical temperature of -273.15 oC turns out to be the same for many different gasses.

• -273.15 oC is not observed experimentally.• We use this extrapolated zero-pressure temperature as a basis

of a new temperature scale with it’s zero at this theoretical temperature. Named after Lord Kelvin 1824-1907

Concept of Heat

• Heat refers to a transfer of energy from one body to another • Heat DOES NOT refer to the amount of energy “contained” in a

body or system.

Heat always flows from the hotter object to the cooler object independent of the amount of “heat energy” each object contains

Specific Heat

• Different substances have different capacities for storing internal energy

• The specific heat capacity of any substance is defined as the quantity of heat required to change the temperature of a unit mass of the substance by 1 degree

• Consider it as “thermal inertia”• The more heat energy it takes to raise a substances temperature,

the more heat energy is given up by the substance as it cools down!!!

Thermal expansion of Materials

• Suppose you have a rod with some initial length Lo at some initial temperature To. When the temperature changes by T, the length will change by an amount L.

• Experiment shows that L is directly proportional to T provided T is less than about 100 oC.

LoL

Water

Chapter 16 – Heat Transfer

• Summary of Terms– Conduction– Convection– Radiation– Newton’s law of cooling– Greenhouse effect– Solar Constant– Solar Power

• Summary of Terms– Conduction– Convection– Radiation– Newton’s law of cooling– Greenhouse effect– Solar Constant– Solar Power

Chapter 17 – Change of Phase

• Summary of Terms– Evaporation– Sublimation– Condensation– Boiling– Melting– Regelation

• Summary of Terms

Change of Phase

• Evaporation• Condensation• Fogs and Clouds• Boiling• Melting and Freezing• Energy and Change of Phase

Change of Phase• Evaporation

– Fast molecules escape the liquid, taking energy, and leaving the liquid cooler.

– Evaporation is a cooling process!• Condensation

– Slow molecules condense leaving the air warmer.– Condensation is a warming process

• Boiling– Boiling is a cooling process– Temperature is 100 degrees C no matter how much heat we

give the water.– Water boils as fast as it is being warmed by heating.– The steam carries away the heat

Energy in Condensation/Vaporization

• The Heat of Vaporization is 540 calories per gram of condensed water at 100 degrees.

Energy and Phase Changes

Energy

Chapter 18 – Thermodynamics

• Summary of Terms– Thermodynamics– Absolute zero– Internal Energy– First law of thermodynamics– Adiabatic process– Temperature inversion– Second law of thermodynamics– Heat engine– Entropy

• Summary of Terms

1st Law of Thermodynamics

• Conservation of energy• When heat flows to or from a system, the system gains or loses an

amount of energy equal to the amount of heat transferred• Heat added to system = increase in internal energy + external work

done by the system• Useful energy degenerates to non-useful forms such as thermal

energy to the environment

Adiabatic Processes

• Compression or expansion of a gas where no heat enters or leaves the system

• If we do work on a system by compression, we heat it up.• When we expand a system we cool it off• Remember blowing on your hands?• Warm air rises, expands, cools and forms clouds

2nd Law of Thermodynamics

• Thermal energy never flows spontaneously from cold object to a hot object.

• A machine cannot be 100% efficient• Entropy of closed systems always increases.

• One of the greatest shortcoming of would-be inventors is lack of understanding of the 1st and 2nd law of Thermodynamics.

Maximum Efficiency of Heat Engine

High Temperature

Low Temperature

Work done

Input Heat

Heat Exhaust

Efficiency

T(K) hot – T(K)cold

Ideal Efficiency = ------------------------

T (K)hot

Entropy

• 2nd Law of Thermodynamics• The entropy of a thermally isolated system never decreases, it can

only increase or stay the same.  • Entropy is a measure of the disorder of a system. 

Chapter 19 – Vibrations and Waves

– Sine Wave– Amplitude– Wavelength– Frequency, Hertz– Period– Wave Speed– Longitudinal Wave– Transverse Wave– Interference Pattern– Standing Wave– Doppler Effect

• Summary of Terms

– Bow Wave– Shock Wave– Sonic Boom

• Amplitude - distance from the baseline to the crest of a wave

• Wavelength - the distance from the top of one crest to the top of the next one

Waves

• Period - the time required for one vibration• measured in seconds

• Frequency - number of vibrations per unit time• measured in Hertz

FrequencyPeriod

1

PeriodFrequency

1

Wave Speed...

• the speed with which waves pass by a particular point• e.g. the speed of a surfer

• It depends only on the type of medium.

• Wave Speed = Frequency Wavelength

Transverse Waves

• side to side vibration in a direction perpendicular to the wave's motion

Longitudinal Waves

• back and forth vibration in a direction parallel to the wave's motion

INTERFERENCE

• Constructive or destructive interference results when waves add.

• Standing Waves - wave pattern produced from interfering waves

– Examples

• Vibrating Strings

• Organ Pipe

Standing Waves

Chapter 20 – Sound

– Infrasonic, Ultrasonic– Compression, Rarefraction– Reverberation (echo)– Refraction (bending)– Forced Vibration– Natural Frequency– Resonance– Interference– Beats

• Summary of Terms

• infrasonic – frequencies < 20 Hz

• ultrasonic– frequencies > 20,000 Hz

• human hearing range – frequencies between 20 Hz and 20,000 Hz

• Sound requires a medium.

– solid, liquid or gas

• Sound waves have compression and rarefaction regions.

SOUND

Refraction of Sound

• Refraction - the bending of a wave

• Sound travels faster in warm air than in cool air.

• Sound waves bend toward cooler air.

Sound Interference

• Overlapping compressions of a sound wave will result in…– …constructive interference.– …and a louder sound.

• Overlapping a compression and a rarefaction results in... – …destructive interference.– …and a softer sound.

• Beats - the periodic variation in loudness of two sounds played together

• The beat frequency is equal to the difference in the frequency of the two sounds.

• What is the beat frequency when a 262 Hz and a 266 Hz tuning fork are sounded together?

Beats