Chapter 7 Energy & Its Forms

What is Energy Energy: the ability to do work Energy is transferred by a force over a distance Also measured in Joules

Types of Energy Kinetic Energy: “energy of motion” Potential Energy: “stored energy”

Kinetic Energy Anything in motion has kinetic energy Depends on an objects mass and velocity KE = ½ mv2 SI Unit: Joule

Potential Energy Depends on the objects position and mass Gravitational Potential Energy: depends upon an object’s height GPE = mgh SI Unit: Joule

Forms of Energy There are 6 main forms of energy. Heat Mechanical (sound) Electromagnetic (light) Chemical Nuclear Electrical

Mechanical Energy Energy associated with motion Examples: waterfalls, speeding trucks, sound, wind

Thermal (Heat) Energy Energy associated with the internal motion of atoms The faster the atoms move…the more thermal energy Causes temperature changes & phase changes (solid-liquid-gas)

Chemical Energy Energy stored in chemical bonds in compounds Examples: digestion, fuel for a car, burning wood

Electrical Energy Energy associated with electrical charges. Example: Lightning

Electromagnetic Energy Energy that travels through space in the form of waves Examples: visible light, X-rays

Nuclear Energy Energy stored in the nucleus of the atom Nuclear fission: energy released when nuclei are split Nuclear fusion: energy released when nuclei are combined

Energy Conversion & Conservation

Law of Conservation of Energy States that: Energy cannot be created or destroyed Energy can only be converted from one form to another

Energy Conversion (Pendulum) KE = zero PE = maximum KE = zero PE = maximum KE = maximum PE = zero

Energy & Mass Albert Einstein discovered the relationship between energy and mass in 1905. The equation E = mc2 shows that mass and energy can be converted into each other c= speed of light (3 x 108 m/s)

Energy Resources

Types of Energy Resources Nonrenewable energy resources: Exist in limited quantities Once used, they cannot be replaced quickly or easily (only over millions of years) Renewable energy resources: Relatively unlimited Can be replaced in a shorter period of time

Nonrenewable Energy Resources Fossil Fuels: formed underground from the remains of once-living organisms Relatively inexpensive, but create pollution & are limited in quantity Examples: Oil, natural gas, coal

Renewable Energy Resources Hydroelectric: energy from flowing water Solar: usable energy from sunlight Geothermal: energy from the heat beneath Earth’s surface (steam) Other: Biomass, Hydrogen fuel cell, wind