Energy Transformations

1. Energy Transformations The law of conservation of energy states that energy is not created nor destroyed, however energy can change from one form to another. There are 3 main forms of energy: Kinetic (motion of particles), Potential (based on position of particles), Radiant(doesn’t require particles)

2. Energy Transformations For example, your car uses gasoline to cause the car to move. Within the bonds of the gasoline molecules is stored energy (potential). The molecules undergo a chemical reaction (also potential) to generate heat (kinetic) which, through a series of simple machines, causes the car to move (kinetic). If you happened to use a solar powered car (rather than gasoline), then you would be using radiant energy to cause the car to move (kinetic).

3. Energy Transformations Kinetic: movement of particles Mechanical: movement of macroscopic particles EX: spinning wheels, moving your finger Thermal: movement of microscopic particles (such as atoms, molecules) EX: heat, movement of helium gas atoms Kinetic thermal energy can be transferred from one particle to another via conduction and convection (there is a 3rd, but we are skipping it for now) see the next slide

4. Energy Transformations Kinetic Thermal Energy Conduction: When particles collide with one another, energy is transferred from the faster (more energy) moving particle to the slower (less energy) moving particle. This makes the slower moving particle increase in speed. In solids, particularly metals, electrons are able to move from atom to atom. Electron flow will increase in speed with addition of thermal energy, increasing the conductivity of a substance. Rate of transfer of thermal energy depends upon the separation of the particles and their freedom to move. Which phase do you think best conducts thermal energy?

5. Energy Transformations Kinetic Thermal Energy Convection: Involves the transfer of thermal energy by the motion of a fluid (a fluid is a liquid or a gas), or by currents. As the fluid is heated from below, the particles at the bottom move faster, causing them to reduce in density (they spread apart) The less dense particles rise to the top, as the denser, cooler (less thermal energy) fluid moves to the bottom, creating a current The convection current will keep stirring this way. The warmer fluid will always move away from the

6. Energy Transformations Potential: based on position of particles (any size) Electrostatic: due to a difference in charge EX: chemical bonds (chemical reactions) electricity, + ion attracted to a – ion to form an ionic compound Elastic: due to deformation of an elastic object EX: stretched spring, stretched rubber band Gravitational: due to attraction to an object with a large mass EX: moon attracted to earth, book falling off desk toward earth

7. Energy Transformations Radiant: energy does not require particles since it travels through electric fields Electromagnetic: light EX: sunlight, light from light bulbs Nuclear: reactions which occur within nucleus of an atom EX: sun (stars) creating other elements from hydrogen, atomic bomb, radioactivity, fusion, fission