CHAPTER 8 TOPICS

• Parts of the Atom• Rutherford vs. Bohr• Periodic Table• Metals/ Metalloids/Non-Metals• Isotopes• Ions and Charges• Forming Compounds

Parts of the Atom

• 1. Proton (+)

• 2. Electron (-)

• 3. Neutron (-)

Chemistry in Color

• Specific elements give color when heated in flame.

• Continuous spectrum - e.g., rainbow• Line Spectrum

Line Spectra

• Held the key to the structure of the atom!

The Bohr Atom

• Bohr: suggested that electrons were responsible for the line spectra. Proposed that electrons traveled around the nucleus of the atom in shells

The Bohr Atom

• Bohr: associated each shell w/ a particular energy level. The farther away, the higher the Energy.

Allowed electrons to jump from one shell to another.(ground state excited state)

Comparison

• Bohr Model similar to model for solar system where the planets revolve in their particular orbits.

• Difference: Electrons can jump from one shell to another. The planets do not!

CHAPTER 5WAVE MOTIONS AND SOUND

• One of the types of energy mentioned in Chapter 3 was Elastic energy.

• An elastic material is one that is capable to recovering its form after a force deforms it.

• As long as the applied force does not exceed the elastic limit, the elastic material will return to its original shape.

• Vibration – is the back and forth motion that repeats itself.

• Almost any solid can be made to vibrate if it is elastic.

• If a mass is attached to a spring, the greater the mass is pulled, the greater the stretch and the greater the restoring force.

• The restoring force us proportional to the displacement and is in the opposite direction of the applied force.

Simple Harmonic Motion

• – is the periodic vibration or oscillation of the mass.

• - is the vibratory motion that occurs when there is a restoring force opposite to and proportional to a displacement.

Definitions

• Amplitude – the extent of displacement from the equilibrium motion

• Cycle – a complete vibration (Ex: From the far left all the way to the far right and back to the far left again.)

• Period – is the time required to complete one cycle.

More Definitions

• Frequency – is the number of cycles per second

• Hertz – is the unit for frequency

WAVES

• 2 Major considerations about a wave:

• 1. A wave is a travelling disturbance.

• 2. A wave transports energy.

2 Kinds of Waves

• Longitudinal Wave – a disturbance that causes particles to move together or farther apart in the same direction that the wave is moving

• Transverse Wave – is a disturbance that causes motion perpendicular to the wave that is moving. Particles involved do not move closer or farther apart. Instead, they go up or down or back and forth perpendicular to the direction of the wave motion.

• Waves that move through the air are longitudinal; so sound waves must be longitudinal waves.

Infrasonic vs. Ultrasonic

• Infrasonic – sounds below 20 Hz

• Ultrasonic – sounds above 20,000 Hz.

• Frequency Range of Human Hearing: is between 20 - 20,000 Hz.

• Pitch – is the interpretation of frequency by the human brain

IMPORTANT FACTS ABOUT SOUND WAVES

• Speed of light is faster than the speed of sound. (Ex. Lightning vs. thunder)

• Sound travels slower through air. (Ex. Thunder)

• Sound travels faster @ higher temps. than at low temps. because the Kinetic E of molecules which transmit impulses is higher at higher temps.

MORE FACTS ABOUT SOUND WAVES

• Generally, the speed of sound in denser materials is faster than in less dense materials.

• Ex. In dry air at 0 oC, sound travels at 331 meters/sec. In steel, sound travels at 5,940 m/s and in lead at 1,960 m/s.

Velocity or Speed of Sound

• Velocity of Sound = wavelength x frequency

• Sound waves are 3D spherical waves that move outward from the source.

• Increased Pressure condensation• Normal pressure• Decreased Pressure rarefaction

• Refraction = sound waves moving through the same material at different conditions like different temperatures

• Reflection = sound waves moving through different materials like walls.

• Reverberation = sounds that bounce back and forth (reflection) and mix with the original sound. Ex. Acoustics of auditoriums

• Sound waves may either be absorbed, transmitted or reflected.

• Echo = a reflected sound that can be distinguished from the original

Sonar

• Is a type of sound wave echo.

• The distance to the surface is one-half the total distance.

• Depth = (1/2) distance

• Intensity = the power (in watts) transmitted by a wave to a unit area (in meters) that is perpendicular to the waves.

• Decibel scale = used to measure the intensity of sound

• 0 decibel = barely heard• 65 decibel = Easy to hear