Final Exam ReviewSpring 2012

Physical ScienceCh. 9: Energy Sources

Fossil Fuels• Fossil fuels are hydrocarbons

(compounds composed of H and C) which are made up of decayed remains of plants and animals. (pg. 258)

• About 85% of all energy used in the U.S. comes from fossil fuels.

• Q. Are fossil fuels renewable resources?

• Fossil fuels are considered nonrenewable resources.

This means that they are not naturally replaced as quickly as they are used.

In order to be renewable, it would need to be replaced nearly as quickly as it is used, like solar power.

Petroleum

Petroleum (crude oil) is a liquid fossil fuel. It comes out of the ground as crude oil, and is

then separated into different petroleum products through a process called fractional distillation. (refining crude oil into usable products)

These products include natural gas, kerosene, gasoline, heating oil, diesel fuel, and lubricating oil.

CoalCoal CoalCoal is a solid fossil fuel. is a solid fossil fuel.

Coal must be either strip Coal must be either strip mined or subsurface mined or subsurface minedmined

It is used as a fuel It is used as a fuel primarily in industries primarily in industries (steel mills, power plants, (steel mills, power plants, etc.).etc.).

It produces pollutants It produces pollutants when it is burned.when it is burned.

Strip Mining• Strip mining uses large scrapers to

remove the surface layers of the earth to get at layers of coal which are close to the surface.

• Strip (or surface) mining is used when layers of coal are close to the surface.

• Identify 2 pro’s and 2 con’s of strip mining.

• Strip mining is a relatively safe, simple and inexpensive means of collecting coal.

However, it is harmful to the environment.

It removes vegetation and habitat, and leads to excessive run-off which can erode the land.

Sub-surface MiningSub-surface Mining

Sub-surface mining is where vertical and/or horizontal shafts are dug into the earth to access underground coal deposits.

Sub-surface mining is better for the environment, but is more expensive and more dangerous for the miners.

Mine collapses and "black lung" are not uncommon.

• Even though they are the most commonly used forms of energy, fossil fuels are generally not considered a desirable energy source.

• They pollute the environment, are limited in supply, and are non-renewable.

Hydroelectric Power

Hydroelectricity is

electricity produced

through the

movement of water.

Hydroelectric power

is usually produced

by turbines housed

in dams.

• Hydroelectric dams are very efficient, and after the initial investment, are relatively inexpensive sources of energy. They also create lakes for recreation and irrigation.

However, they also can disturb an ecosystem and are quite expensive to build.

Solar Energy• Solar power is produced

by photovoltaic cells (devices which convert solar energy into electricity).

• Solar energy is free (sort of), renewable, and abundant.

However, it is unpredictable and not practical in all locations

Nuclear Energy Nuclear energy is created

when a controlled fission reaction (the splitting of nuclei of radioactive atoms) releases a tremendous amount of energy which is used to heat water and produce steam power.

• Barring human error, nuclear power is very safe. It also produces no pollution.

• However, if an accident were to occur, the potential is there for very severe results.

• The main problem is safely The main problem is safely disposing of nuclear waste disposing of nuclear waste without harming people or the without harming people or the environment.environment.

• Nuclear waste from U.S. power plants is transported to Yucca Mountain in Nevada, where it is buried deep within the mountain.

Wind Energy

• Wind energy is where the kinetic energy of wind is converted into electricity. Large windmills (turbines) are used to harness this energy.

• Biomass fuels are any type of organic matter (wood, grasses, sugar cane, corn, soybeans, etc.) which can be burned to produce energy.

• Some biofuels are burned directly to produce heat, or used to boil water to produce steam which can turn turbines and generate electricity.

Others are refined and used as fuels, such as ethanol and biodiesel, to power vehicles.

• Biofuels are renewable resources and produce relatively low amounts of pollution.

However, they typically do not burn as efficiently as fossil fuels and may contribute to deforestation in certain areas.

Physical ScienceCh. 10: Waves

• A wave is a rhythmic disturbance which carries energy through space or matter.

• Many waves, but not all, require a medium to move between points.

A medium is a material through which a wave transfers energy.

Types of Waves

• Based on the way they move, there are 2 different types of waves:

1. Transverse Waves

2. Compressional Waves

Transverse Waves• In a transverse wave, the wave's medium

move perpendicular to the direction of the wave. Ex. ocean waves, light waves

• For example, as the wave moves left to right, the medium moves up and down.

Parts of a Transverse WaveThere are 4 main parts to a transverse wave:

• Crest- the highest point on a transverse wave

• Trough- the lowest point on a transverse wave

 

• Amplitude- the distance from either the crest or trough to the resting point of the wave

• Wavelength- distance from crest to crest or trough to trough on a wave

Wave Frequency• Frequency is a property of a wave, not a

part of one.

• Frequency is the number of waves which pass a given point in 1 second.

• Hertz (Hz) is the SI unit for frequency.

1 Hz = 1 wave passing a given point in

1 second

• When you tune in to a radio station, the numbers on the dial represent the frequency that a particular station is sending their signal out at.

FM – MHz (megahertz), 98.9 = 98,900,000 Hz

AM – KHz (kilohertz), 610 = 610,000 Hz

• The period of a wave is the amount of time it takes one wavelength to pass a stationary point. The wave below has a period of about 2 s.

Compressional Waves A compressional wave vibrates in the

direction that the wave is travelling. Examples: slinky, sound waves

• The 2 main parts of a compressional wave are:A. Compression- area of higher density

within the wave

B. Rarefaction- area of lower density

within the wave pg. 296

Reflection and Refraction• Reflection is where a wave strikes an object and

bounces off.• When a wave strikes a flat reflective surface it will

reflect back at the same angle that it struck the surface at. This is called………

The Law of Reflection

• The law of reflection states that the angle of incidence is equal to the angle of reflection on a flat reflective surface.

• In addition to reflection a wave can experience refraction.

Refraction is the bending of a wave as it enters a different medium, due to a change in speed.

Physical Science Chapter 11: Sound

Sound Waves Sound waves are a type of compressional wave which require a medium to travel.

The study of sound is called acoustics.

• Sound waves travel at about 750 mi/hr. This speed is effected slightly by the type of medium, temperature of medium (directly proportional), and elevation.

• When an object such as a jet travels at a speed greater than 750 mi/hr it is said to be supersonic.

• What happens when an object travels at supersonic speeds?

Pitch• Pitch is how high or how low a sound is to

the human ear.

This is determined by the sound frequency, which is directly proportional to the sounds pitch.

pitch frequency

pitch frequency

Humans can only hear sounds which are within a certain range. For the average person this range is from approximately 20 Hz to 20,000 Hz (vibrations per second).

• Frequencies above 20,000 Hz, and beyond the normal range of human hearing are called ultrasonic.

• Sounds below the normal range of human hearing (20 Hz) are called subsonic.

LoudnessLoudness is human perception of sound intensity (the amount of energy in the wave), and is measured on the decibel scale.

Loudness is subjective to the individual. However, the decibel scale still assigns numeric values to different levels of loudness.

• Very high frequency sound waves can be used in the medical field.

• Ultrasonic waves can be used to break up kidney stones and gall stones.

Doppler Effect

• The Doppler effect is a change in wave frequency due to a moving wave source.

• The frequency is higher in the direction that the wave source is moving and lower in the opposite direction.

A bug swimming in a pool of water produces waves which exhibit the doppler effect.

• Other examples of the Doppler effect include radar guns, sounds produced by a racecar or an ambulance, and Doppler radar.

Doppler radar uses radio waves to detect winds, clouds, and precipitation in order to identify and forecast weather.