Energy: Forms and Changes

Nature of Energy Energy is all around you! – You can hear energy as sound. – You can see energy as light. – And you can feel it as wind.

Nature of Energy You use energy when you: – hit a softball, – lift your book bag, – compress a spring,

Nature of Energy Living organisms need energy for growth and movement.

Nature of Energy Energy is involved when: – a bird flies. – a bomb explodes. – rain falls from the sky. – electricity flows in a wire.

Nature of Energy Energy can be defined as the ability to do work. – If an object or organism does work (exerts a force over a distance to move an object) the object or organism uses energy.

Nature of Energy Because of the direct connection between energy and work, energy is measured in the same unit as work: joules (J). In addition to using energy to do work, objects gain energy because work is being done on them.

States of Energy: Kinetic and Potential Kinetic Energy is the energy of motion. Potential Energy is stored energy.

TYPES OF ENERGY MSCHEN Mechanical, Solar (Electromagnetic), Chemical, Heat (Thermal) Electrical, Nuclear

Mechanical Energy o Kinetic or potential energy from the motion or position of an object. Examples: A bowling ball has mechanical energy. When the ball strikes the pins, mechanical energy is transferred to the pins!

Mechanical Energy When you kick a football, you give mechanical energy to the football to make it move. The total mechanical energy in a object is: The potential + kinetic energy that it has.

Examples of Mechanical Energy

SOLAR (Electromagnetic) Energy o Light energy o Includes energy from radio waves, microwaves, infra-red, visible light, ultraviolet, X-rays, gamma rays

Chemical Energy o Energy that is available for release from chemical reactions. The chemical bonds in a matchstick store energy that is transformed into thermal energy when the match is struck.

Chemical Energy Chemical Energy is required to bond atoms together. And when bonds are broken, energy is released.

Examples of Chemical Energy Fossil fuels Batteries Sugar (all food)

Heat Energy The internal motion of the atoms is called heat energy, because moving particles produce heat. Heat energy can be produced by friction. Heat energy causes changes in temperature and phase of any form of matter.

Electrical Energy oEnergy caused by the movement of electrons o Easily transported through power lines and converted into other forms of energy

Nuclear Energy When the nucleus splits (fission), nuclear energy is released in the form of heat energy and light energy. When nuclei collide at high speeds and join (fusion), heat and light energy is also released.

Nuclear Energy The sun’s energy is produced from a nuclear fusion reaction in which hydrogen nuclei fuse to form helium nuclei.

Nuclear Energy Nuclear energy is the most concentrated form of energy.

QUIZ TIME! 1. What type of energy cooks food in a microwave oven? ELECTROMAGNETIC ENERGY 2. What type of energy is the spinning plate inside of a microwave oven? MECHANICAL ENERGY

QUIZ TIME! 3. What kind of energy is transported to your house through power lines? ELECTRICAL ENERGY 4. When you plug an electric fan to a power outlet, electrical energy is transform into what type of energy? MECHANICAL ENERGY

QUIZ TIME! 5.What energy transformation occurs when an electric lamp is turned on? ELECTRICAL ENERGY TO: ELECTROMAGNETIC ENERGY (or LIGHT or SOLAR)

6. What 2 types of energy are shown in the picture? Mechanical and Thermal Energy (Don’t forget friction)

7. What type of energy is in a tree? Chemical Energy

8. What 3 types of energy are shown in the picture? Electrical, Mechanical and Electromagnetic Energy

9. What type of energy is in a tomato? Chemical Energy (yummy)

10. What type of energy is in the flames of a fire? Thermal Energy (and Light)

Three main concepts of: The Law of Conservation of energy 1. There is a total set amount of energy in the universe. 2. All energy is conserved. It cannot be created or destroyed 3. All forms of energy are interchangeable - can be changed from one form to another

Conservation of Energy Heat energy is usually a bi-product of energy transfer Chemical (Photosynthesis) Heat Energy (E Tax) Electromagnetic Energy (Light) Heat Energy (E Tax) Nuclear Energy (sun)

Electromagnetic Energy Nuclear Energy Electrical Energy Heat Energy Chemical Energy Mechanical Energy All Forms of Energy are Inter-changeable DVD: Energy (Discovery)

Collision creates heat!

Energy & Friction Friction turns mechanical energy into heat

Heat Energy Heat energy is transferred through 1.Conduction (contact) 2.Convection (liquids & gases) 3.Radiation (energy waves)

Conversion 1: Nuclear  Electromagnetic & heat energy Heat Light (EM) Nuclear

Conversion 2: Light  Chemical (Photosynthesis) Chemical (Photosynthesis) Nuclear, Electromagnetic & Heat

Conversion 3 In an automobile engine, fuel is burned to convert chemical energy into heat energy. The heat energy is then changed into mechanical energy to move the pistons

Chemical  Heat  Mechanical

Draw a flow map showing the flow of energy transformations in a car from starting vehicle to driving. You should have 5 different types of energy.

Energy Transfer Chemical Electrical Sound (mechanical) Light (Electromagnetic) Thermal Mechanical

States of Energy: Kinetic and Potential Energy Kinetic Energy is the energy of motion. Potential Energy is stored energy.

Kinetic Energy The energy of motion is called kinetic energy. The faster an object moves, the more kinetic energy it has. The greater the mass of a moving object, the more kinetic energy it has. Kinetic energy depends on both mass and velocity.

Kinetic Energy The formula to solve for kinetic energy is: K.E. = ½ mass x velocity 2 What has a greater affect on kinetic energy, mass or velocity? Why? Velocity. Because the number is squared. 3 times more velocity = 9 times more energy 3 2 = 9

Potential Energy Potential Energy is stored energy. – Stored chemically in fuel, the nucleus of atoms, and in foods. – Or stored because of the work done on it: Stretching a rubber band. Winding a watch. Pulling back on a bow’s arrow. Lifting an object high in the air.

Elastic Potential Energy Energy that is stored due to being stretched or compressed Examples :

Gravitational Potential Energy Potential energy that is dependent on height and mass

Gravitational Potential Energy “The bigger they are the harder they fall” is not just a saying. It’s true. Objects with more mass have greater G.P.E. The formula to find G.P.E. is G.P.E. = Weight X Height. (mass x gravity) (height) (mass)(gravity)(height)

Gravitational Potential Energy If you stand on a 3- meter diving board, you have 3 times more G.P.E, than you had on a 1- meter diving board.

The most common form of energy change is between potential energy and kinetic energy Kinetic-Potential Energy Conversion

Ball slows down Ball speeds up

Kinetic-Potential Energy Conversion Roller coasters are pulled mechanically up the tallest hill, giving them a great deal of potential energy. From that point, there are conversion between potential and kinetic energy throughout the entire ride. 5_int_rollercoaster/

Kinetic vs. Potential Energy At the point of maximum potential energy, the car has minimum kinetic energy.

Law of Conservation of Energy Energy cannot be created or destroyed, only converted or transformed from one type of energy to another End up with the same amount of energy you started with. Total Energy = Potential + Kinetic + heat (from friction) (heat is a form of kinetic)

All Energy is Conserved Conserved Remember, This form of Kinetic Energy as well as Gravitational Potential Energy & Elastic Potential Energy are all forms of Mechanical Energy. KE + GPE + EPE = ΣE (ΣE = Sum of all energies) Notice “No air friction” so no heat in this example Demo: talk about the different forms of energy in the diagram (KE, GPE, EPE). Freeze frame the projector – add it up. Repeat 1-2 times.