Energy Transformations

Natural Gas

A fossil fuel byproduct formed with coal and oil.

Coal

A fossil fuel formed from land plants.

Oil

A fossil fuel formed from marine plants.

Dual Nature

Light has both a wave nature and a particle nature.

Visible Light

Light, with frequencies that humans can see. Ex: A rainbow.

Photovoltaics

Panels collect sunlight and turn the energy into electricity.

Acid Rain

Rain with a lower pH than neutral. Acid rain is corrosive to many substances, including rocks. Often caused by pollution. Ex: sulfur dioxide dissolves in the water droplets of clouds to make sulfuric acid.

Renewable Resources

Resources which replenish at the same (or faster) rate than the rate at which they are used. Ex: wind energy, solar energy, hydroelectric power.

Non-Renewable Resources

Resources which will be depleted faster than they can be replenished. Ex: Natural gas, petroleum.

What is the source of energy on which most living organisms on Earth ultimately depend?

Solar radiation. - The sun emits solar radiation, which is captured by producers. These form the base of the food chain. Most living organisms on Earth ultimately depend on the sun's solar radiation.

Threshold of Pain

Sound at 120 dB.

Compression Wave

A longitudinal wave with areas of high and low pressure, or density. Ex 1: Sound. Ex 2: Which of the following can be true of compressional waves with a high frequency? Answer: They are sound waves with a high pitch.

Insulator

A material that prevents or limits the flow of electricity or heat. Ex: glass, air.

Excited Electrons

Electrons in orbitals higher than the ground state.

Hydroelectric Energy

Energy collected as gravity pulls water from higher elevations to lower elevations. Ex: The Hoover Dam.

Solar Energy

Energy from the sun in the form of electromagnetic radiation.

Turbine

A device that transforms energy into kinetic energy.

Generator

A device that uses electromagnetic induction to produce an electrical current. Ex: The Generator in a car.

Circuit Diagram/Schematic

A drawing that uses symbols to show how components should be connected in a circuit.

Threshold of Hearing

0 dB, the softest sound a human can hear.

Phase Change

A change of state of a substance. Ex: A gas to liquid.

Electromagnet

A coil of wire that is magnetic because current flows through it. Ex 1: solenoid. Ex 2: Electromagnetism is possible because: Answer: Positive and negative charges exist. - All electromagnetism depends upon the existence of electrical charge. Electricity is possible because opposite charges attract each other and similar charges repel. Moving electrical charges produce magnetism. Ex 3: Electromagnets can be formed entirely from nonmagnetic materials. How can an electromagnet have magnetic properties if electricity and magnetism are not the same thing? Answer: Charges in the nonmagnetic material become magnetic when they are moving. - All moving charges have a magnetic field. Once the charges stop moving, the magnetic field disappears. Ex 4: Which of the following devices operates mainly because of an electromagnet? Answer: An audio speaker. - Audio speakers are made from a coil of wire that is free to move inside the poles of a permanent magnet. An audio signal causes the current to switch back and forth, and the movement of the coil pushes air molecules back and forth, making sound. Ex 5: An electromagnet can be formed from a copper wire wound around the nail. What else is required for the electromagnet to become magnetic? Answer: A power supply so current will flow in the wire. - A current must flow (moving charges) for a magnetic field to be produced. If no power supply is attached to the wire, the electromagnet will not have magnetic properties.

Short Circuit

A dangerous circuit in which a conducting wire is connected directly across the two battery terminals. Ex: The circuit diagram shown has a battery, two lamps, a switch and several conducting wires, however when the switch is closed, the lamps will not light and the battery will get hot. There is something wrong with the circuit. What is this kind of circuit called? Answer: Short circuit. - A conducting wire connects directly across the battery. A conducting wire has no resistance to the flow of current, so all of the current will flow through the wire and none will flow through the lamps. A short circuit can be dangerous as the battery will try to supply an infinite amount of current and the system could get very hot.

Resistance

A device that reduces/limits/controls the current in a circuit, measured in ohms. Ex 1: 10 ohms (10 Ω). Ex 2: Of the choices listed, which is the best analogy for resistance in a circuit? Answer: Security screening at the airport. - Resistance can be modeled as security screening at the airport, which reduces the number of people that get through the airport. Resistance in a circuit reduces the current, which is flow of charge.

Combustion Motor

A device that transforms chemical energy into mechanical energy. Ex: A car engine.

Neutral (Charge)

A material without a net positive or negative charge. Ex 1: Neutrons. Ex 2: Neutral sodium atoms become positively charged sodium ions when: Answer: An electron is removed from the atom. - All electrons have a negative charge of -1. Removal of one negatively charged electron from a neutral sodium atom leaves the sodium with a positive charge of +1.

Conductor

A material, often metal, through which electrons can move freely. Ex: copper wire.

Fossil Fuels

A natural non-renewable fuel source. derived from underground, fossilized (petrified) remains of living organisms. Ex 1: Natural gas, petroleum, coal. Ex 2: Which of the following scenarios would have the greatest chance of forming fossil fuels? Answer: An aquatic organism that falls to the bottom of a small pond. - In a stagnant body of water, a high accumulation of sediments buries the organisms and protects them from being decomposed or eaten by other organisms. As the sediments accumulate over a long period of time, this increases heat and pressure and creates oil and gas.

Photon

A particle of light energy. Ex: A particle nature of light.

Condensation

A phase change from the gas state to the liquid state. Ex: humidity condensing on a cold glass of tea.

Evaporation

A phase change from the liquid state to the gas state. Ex: When water boils and turns to steam.

Freezing

A phase change from the liquid state to the solid state. Ex: coconut oil solidifies at 76 degrees fahrenheit.

Melting

A phase change from the solid state to the liquid state. Ex: mercury melts at -38 degrees fahrenheit.

Nuclear Fusion

A process in which the nuclei of light elements, like hydrogen, fuse together to create the nuclei of heavier elements, like helium. Ex: reactions within the sun.

Sublimation

A pure solid changes directly into a gas.

Diffuse Reflection

A reflection in which no image is seen. Ex: The reflection from a wall.

Specular Reflection

A reflection that looks like the image. Ex: mirrors.

Sound

A series of high and low pressure regions. - Is a longitudinal wave. * Sound is a disturbance carried by a vibrating medium, therefore it is a wave. Sound waves cause the medium to vibrate along the same axis as the sound moves, therefore it is longitudinal.

Nearsightedness

A vision problem in which a person cannot see distant objects without correction because their eyeball is too long. Nearsightedness is corrected with diverging lenses.

Farsightedness

A vision problem in which a person cannot see nearby objects without correction. Farsightedness is corrected with converging lenses.

Ion

An atom with a net electrical charge because it lost or gained an electron. Ex: H+ ion has a +1 charge.

Charge

An electric property of matter that produces interactions with an electric field; can be positive or negative. Ex: protons, electrons.

Telescope

An optical instrument that often uses two convex lenses to form a virtual image of a distant object.

Compound Microscope

An optical instrument that often uses two thick convex lenses to magnify very small objects.

Dark Energy

An unknown source of energy that is thought to fuel the ever-increasing expansion of the Universe.

Sound waves and seismic waves are alike because they:

Both travel only through a medium.

Potential Energy

Energy that is stored in the position or configuration of objects. Ex 1: A ball on top of a hill; two positive electrical charges close together. Ex 2: Casey is playing with her yo-yo. She performs an "around the world" trick, in which the yo-yo travels up and around in a circle before returning to her hand. At which point in its circular path would the yo-yo have the least potential energy? Answer: When the yo-yo is at the bottom of its circular path. - Gravitational potential energy increases as the object gets farther away from the ground. Since the yo-yo is closest to the ground at the bottom of its path, that is the location where it has the least potential energy. Ex 3: A large round boulder is pushed from point X on the illustration, near the top of a steep hill, and rolled to the bottom. Assuming the boulder and the hill are a closed system, and neglecting any effects from friction, if the boulder has 800 J of potential energy at point X, how much and what type of energy will it have at the bottom of the hill at point Z just before it stops? Answer: At point Z the boulder will have 0 J of potential energy and 800 J of kinetic energy. - Potential energy is energy an object has due to its position or configuration. Kinetic energy is the energy of an object's motion. At point X, the energy is all potential because the boulder is not moving. As the boulder rolls down the hill, its height decreases and its speed increases, so its potential energy decreases and its kinetic energy increases. At point Z at the bottom, the potential energy (and height) are both 0 and all 800 J of the initial energy is kinetic. Ex 4: A large round boulder is pushed from the top of a steep hill and rolled to the bottom. Which point on the illustration shows the greatest potential energy as the boulder rolled down the hill? Answer: point X. - Potential energy is the boulder's energy due to its position (height in this case) or the arrangement of its particles. Of the points listed, point X is the highest point above the ground; therefore, the gravitational potential energy is a maximum at point X. Ex 5: A pendulum swings back and forth in a vertical semicircle pattern. When does the pendulum have its greatest potential energy? Answer: When the pendulum is at the top of the arc. - Potential energy is the energy stored in an object by virtue of an object's position relative to other objects. At the top of the arc the pendulum has its maximum height, therefore it has its maximum potential energy.

Chemical Potential Energy

Ex: A battery. - Chemical energy is energy stored in the bonds of a chemical compound. The breaking of the chemical bonds releases energy. In a battery, energy in the chemical bonds becomes electric potential energy.

Greenhouse Gases

Gases which, when present in elevated quantities in Earth's atmosphere, trap solar radiation and cause the planet to warm. Ex: carbon dioxide.

Gina said "sound waves only travel through a medium." Fernando disagrees, saying "no, sound can travel through a vacuum like the vacuum of space." With whom do you agree, and why?

Gina, because sound is a series of high and low pressure regions and pressure only exists in a medium. - Sound is a series of high and low pressure regions. Pressure has no meaning when no particles are present. When alternating high and low pressure regions reach our ears, our eardrums vibrate and send signals through our nerves to our brains.

Thermal Energy

Heat energy. Ex: The motion or vibration of particles of matter. - Stored in the vibrations of atoms and molecules in matter.

Radiation

Heat transfer by an electromagnetic wave. Ex: standing by a hot fire.

Pitch

How high or low the sound seems to a human ear. Ex: Which of the following characteristics of a sound wave is most related to the frequency of the wave? Answer: Pitch. - The frequency of a sound wave is directly related to pitch. The higher the frequency, or number of waves that pass a given point in one second, the higher the pitch.

Conservation of Energy

In a closed system, the total amount of energy is constant, even if it changes form or moves from one place to another. Ex 1: A girl diving off a board into water. Ex 2: Mr. Hirohoto ties a weighted Superman figure to the end of a long spring hanging from the ceiling. He lifts the action figure and lets it go. The figure repeatedly bounces up and down. Mr. Hirohoto asks his students to describe what they observe about its motion. "Where is Superman moving the fastest?" he asked. "Does he stop anywhere?" "Why do you think he speeds up and slows down?" "Tell me how Superman's height changes." Which science concept is Mr. Hirohoto most likely introducing to his class? Answer: The conservation of energy. - Mr. Hirohoto is introducing a discussion of the conservation of energy by demonstrating the transformations from potential energy to kinetic energy and back.

Boiling Point

Temperature at which evaporation and condensation occur; a physical property of a substance. Ex 1: 100 degrees celsius for water. Ex 2: A liquid is heated to its boiling point temperature. If further heat is added to the liquid it will: Answer: Stay at its boiling point temperature until all of the liquid has evaporated. - When heat is added to a liquid at its boiling point temperature, the heat energy breaks the bonds holding the atoms together as a liquid rather than raising the temperature of the liquid. The temperature remains at the boiling point temperature until all of the liquid has evaporated.

Melting Point/Freezing Point

Temperature at which melting and freezing occur; a physical property of a substance. Ex 1: 32 degrees fahrenheit for water. Ex 2: What happens to a liquid when its temperature cools to its melting point temperature? Answer: It begins to solidify. - The melting point is the temperature at which solids begin to melt into liquids and liquids begin to condense into solids. The melting point is also called the freezing point.

Energy

The ability to do work or apply a force that moves something through a distance. Ex: gasoline.

Intensity

The amount of energy transported by a wave, measured in decibels (dB). Ex: ordinary conversation is about 50 dB. - The unit of intensity is decibels, abbreviated dB. - Related to the amount of energy transported by a sound.

Refraction (of light)

The bending of a light ray's direction of travel as it passes from one material to another. Ex: A pencil looks bent when placed in water.

Reflection (of light)

The bouncing of light off of a surface. Ex: When light reflects off of a mirror.

Energy Transformation

The change of one type of energy into another type. Ex 1: Sledding down a hill -> potential energy into kinetic energy. Ex 2: Energy can be transformed from one type to another. What type of energy transformation is most likely occurring when you turn on a light switch? Answer: Electrical to light. - When you turn on a light switch, you are completing a circuit which is transferring electrical energy into light energy. Ex 3: Which of the following energy transformations occurs when wood burns? Answer: Chemical energy into thermal energy. - When wood burns, chemical energy stored in atomic bonds is converted into heat energy. Ex 4: Which of the following best summarizes the energy transformations that occur in a car engine while the engine is running? Answer: Chemical energy to mechanical energy. - Chemical energy stored in the fuel is converted to thermal energy when the fuel is burned. The thermal energy, in turn, is converted to mechanical energy.

Voltage/Potential Difference/Potential

The difference in energy per charge across any two points in a circuit, measured in volts (V). Ex 1: 9 volts (9 V). Ex 2: Of the choices listed, which is the best analogy for voltage in a circuit? Answer: The height difference between the top and bottom of a hill. - Voltage is related to the potential energy of the charges in a circuit. For example, charges at one terminal of a disconnected battery have the "potential" to make current flow as soon as the battery is connected.

Kinetic Energy

The energy of motion. Ex: A person running; molecules vibrating.

Electromagnetic Spectrum

The entire range of frequencies of electromagnetic waves from very long radio waves to very short gamma rays. Ex: infrared, ultraviolet.

Electric Current

The flow of electrons through a conductive material.

Current

The flow rate of charge, measured in amps (A). Ex: 3 amps (3 A).

Loudness

The human perception of the intensity of a sound. Ex: An industrial noise at 110 dB sounds very loud.

Electron Transitions

The movement of electrons from the ground state in atoms to higher orbitals and back due to the absorption and emission of energy. Ex: Neon lights.

Energy Transfer

The movement of energy from one object or place into another. Ex 1: A cue ball hitting a billiard ball, transfers kinetic energy. Ex 2: Of the concepts about light listed, which concept is the most important for students to grasp because it applies across all science disciplines? Answer: Light carries energy from one place to another. - Energy is considered a cross-cutting concept, meaning it applies to all science disciplines. That energy is carried by light is important not only in the physical sciences, but in life science (photosynthesis), earth science (weather), and space sciences (optical telescopes). Ex 3: When a panel absorbs energy from the sun to power a yard light, which of the following best describes the transfer of energy? Answer: Solar energy to light energy. - Energy from the sun is known as solar energy. Solar panels absorb the energy, which is transferred to light through the panel and circuits in the lamp.

Heat Transfer

The movement of thermal energy from one material to another. Ex: Your hands on hot coffee cup.

Joule (J)

The units of heat and energy in the SI system (metric system).

Magnetic Poles

The north and south ends of a magnet. Ex: Two north magnetic poles repel each other and a north and south magnetic pole attract each other. What happens if you put a negatively charged balloon very close to either pole of a magnet? Answer: Neither pole of the magnet will attract the balloon. - Neither pole of the magnet will attract the balloon. Stationary magnetic poles do not attract or repel stationary electric charges because poles and charges are not the same thing. Poles are not positively or negatively charged. Poles are either north or south and attract or repel only other north and south poles.

Why does a red dress appear red when white light shines on it?

The pigments in the red dress reflect red light and absorb most other colors. - We see the color of the light that is reflected from a colored object. Pigments in the red dress reflect red and so we see red. Most of the other colors are absorbed by the pigments, so we do not see those colors.

Magnetic Field

The potential magnetic force in the space surrounding a magnet. Proportional to the force on a magnetic pole in the space around the magnet.

Photosynthesis

The process where plants use light, water, and carbon dioxide to make their own food (sugar) and oxygen. Ex: Which of the following types of energy do plants convert to chemical energy using photosynthesis? Answer: Light.

Mechanical Energy

The sum of potential and kinetic energy in a mechanical system. Mechanical energy = kinetic energy + potential energy. Ex: A system has 45 J of kinetic energy and 15 J of potential energy. What is the mechanical energy of the system? 45 J + 15 J = 60 J

Convection

The transfer of heat by a moving fluid, like air and water. Ex: heat rising from a lit candle.

Conduction

The transfer of thermal energy through a material or between two materials that are touching. Ex: A heating pad.

Foot-Pound (Ft⋅Lb)

The unit for energy in US customary units.

Ohms (Ω)

The unit for resistance.