Energy!Energy!Energy!Energy!

The ability to do workThe ability to do work

Types of energy• Nuclear• Mechanical

– Potential– Kinetic

• Electromagnetic (Solar/Light)

• Electrical• Chemical• Thermal (Heat)

Nuclear• Nuclear energy is created from reactions

in the nucleus of the atom:

Nuclear– Fusion – Atoms combining into one atom– Fission – An atom splitting apart– Radioactivity - an atom decaying (losing

part of its nucleus)

Mechanical Energy

Energy relating to the motion or position of an object

Mechanical Energy has two forms: Kinetic & Potential

Potential and Kinetic• Potential: stored

energy– It has the potential to do

work, but it is not in the action of doing any work.

• Kinetic: energy of motion– Energy that is actively

doing work.

Examples of Mechanical Energy:

• Sound – molecules of air hitting your ear drum causing it to vibrate.

• Hydroelectric – Water pressure causing a turbine to spin

• Friction – rubbing objects together creating heat.

• Wind – Molecules of air moving and colliding with objects.

Electromagnetic (Light)• Waves of energy that travel through space

from the sun and stars• Different wavelengths carry different

amounts of energy• We only see a small portion of the spectrum

Electrical• Movement or flow of electrons

– Electrons carry a charge

Chemical• Energy stored in the form of

chemical bonds

Chemical

Fe2O3 + 2Al → 2Fe + Al2O3

Reactants Products

Special type of chemical reaction:

Combustion!

Burning natural gas: CH4 + O2 CO2 + H2O

Burning propane: C3H8 + O2 CO2 + H20

Burning gasoline: C8H18 + O2 CO2 + H20

Hydrocarbon + oxygen carbon dioxide + water

Endothermic and Exothermic Reactions

• Breaking bonds between atoms uses energy– this is an Endothermic process

• Making bonds between atoms releases energy– this is an Exothermic process.

• In a chemical reaction, bonds are both made and broken. Sometimes the net result will be endothermic, and sometimes it will be exothermic.

Most Chemical reactions need something to get started –

Activation Energy

Heat (thermal)• Movements of atoms in a

substance

Heat (thermal)• Heat vs. Temperature

– Temperature is the average speed of the molecules. The faster the molecules move, the higher their temperature.

– Heat is the energy that flows due to temperature differences.

– The Amount of the substance will affect heat but not temperature.

Heat (thermal)

40 degrees Celcius 90 degrees Celcius

Which has a higher temperature? Which has more heat? (Hint – which will warm you up more?)

Heat transfer• Conduction

– Heat transferred through direct contact between substances

• Convection– Heat transferred by currents moving in a

gas or liquid

• Radiation– Heat transferred by electromagnetic waves

Energy Transfer• Energy is constantly converting

from one form to another

Energy Transfer• Law of Conservation of Energy:

Energy is neither created nor destroyed – it is converted.

• Nothing is 100% efficient

Here electrical energy is being converted to:

____________

But what other conversions are happening?

Here electrical energy is being converted to:

________________

But what other conversions are happening?