1. Chapter 4: Energy
1. Definition
Energy = the ability of a physical system to dowork on other physical
systems
physical quantity, abbreviation: E, unit of measurement: J
2. Different forms of energy
chemical energy: decomposing of molecules, digestion
thermal energy: reactions in which warmth is set free
mechanical energy: energy associated with the motion and position of an object
electrical energy: energy produced by electricity
see exercise
3. Energy sources
= all sources delivering energy
2 groups:
- fossil energy sources: coal, petroleum, natural gas
- renewable energy sources: solar, wind, hydroelectric, agricultural
biomass, geothermal, tidal

2. 4. Origin of energy
Photosynthesis – see working scheme