Download Energy Unit Class Notes

Energy Unit Class Notes
Energy – the ability to do work (joules)
- kinetic and potential
Types of Energy
1. Mechanical – the energy of movement or position (KE + PE)
- sound is an example of mechanical energy
2. Thermal (heat) energy – total energy of the moving molecules within a substance
Temperature – the average kinetic energy of the atoms of a
substance
Heat – the transfer of thermal energy between objects that have
different temperatures (high concentration to low concentration)
3. Chemical energy – energy stored in the chemical bonds of a fuel
Energy is released when the chemical bonds are broken during a
chemical reaction
Examples: fossil fuels, food, match
4. Electricity – the energy of moving electrical charges (electrons)
Example – lightning
5. Electromagnetic energy – energy that travels in waves and has some electrical
properties and some magnetic properties
Examples: visible light, ultraviolet rays, radiowaves
6. Nuclear energy – energy stored in the nucleus of an atom
Fission – nucleus splits releasing energy (uranium in nuclear
power plants)
Fusion – hydrogen nuclei join together to form helium on the sun
Energy Conversion – a change of one form of energy to another
Fossil Fuel: a material that stores chemical potential energy
The material is ancient plant/animal remains
The original energy is from the sun gained through the process of
photosynthesis
Nuclear energy → Electromagnetic energy (light) → Chemical energy
Examples: coal, petroleum (oil), natural gas
Combustion: the burning of fuel that converts chemical energy to thermal
energy
Temperature scales:
temperature
kelvin degree Celsius degree Fahrenheit
symbol
K
boiling point of water 373.15
°C
°F
100.
212.
melting point of ice
273.15
0.
32.
absolute zero
0.
-273.15
-459.67
Methods of Transferring Heat
1. Conduction – movement of heat from one particle of matter to another by direct
contact
Metals – good conductors of heat
Wood, plastic, cloth – poor conductors of heat
2. Convection – heat transfer by the circulation of fluid currents (liquid and gas)
Molecules in warm air/water move around more, expand, become less
dense and rise (float)
Molecules in clod air/water are denser (more packed) and sink
3. Radiation – transfer of energy by electromagnetic waves (infrared)
Can be through matter or through space (no matter)
The Sun’s heat reaches us by radiation through space
Insulation – a substance that slows down or prevents the transfer of thermal energy
calorie – the amount of heat needed to raise the temperature of one gram of water 1ºC
1 Calorie = 1000 calories
Calorimeter – measures the amount of heat transferred when a substance burns