1. Energy Conversions
Section B.2.5 (p190 – 195)

2. Lesson Outline Evidence of Energy Conversions
Energy Conversions in Natural Systems
Energy Conversions in Technological Systems
Nuclear Energy Conversions
Solar Energy Conversions

3. Evidence of Energy Conversions
From the Law of Conservation of Energy we learned that energy cannot be created from nothing or destroyed BUT that it can change from one form to another.
Some examples of Energy conversions:
A falling object (gravitational potential  kinetic)
A burning log in the fireplace (chemical  thermal)
An internal combustion engine (chemical  kinetic)

4. Evidence of Energy Conversions
Several things might happen when energy being converted from one form to another.
Motion: the most obvious evidence that energy conversion to kinetic energy has happened.
Change in position: Specifically related to how high it is above the Earth’s surface. (gravitational potential)

5. Evidence of Energy Conversions
Several things might happen when energy being converted from one form to another.
Change in shape: can either relate to an object being deformed from a force acting on it OR its elastic potential energy. (springs, trampolines, etc)
Change in temperature: Otherwise known as HEAT, the transfer of kinetic energy from the particles of one substance to another. Remember that heat always flows from hotter objects to cooler objects.

6. Energy Conversions in Natural Systems
The original source for nearly all the energy we use on the Earth is from the conversion of hydrogen into helium in the Sun’s core.
This nuclear energy is converted into solar and thermal energy (heat).
The solar energy travels through space and is absorbed by the Earth and its atmosphere.
The solar energy is then converted to heat, chemical energy (photosynthesis), and kinetic energy (weather and ocean currents)

7. List all the energy conversions (in order), starting from the solar energy from the Sun to the final use of fossil fuels.

8. Is all the solar energy that strikes plants stored as chemical potential energy in fossil fuel? If not, where would energy be lost in this process…

9. What is the main difference between photosynthesis and respiration or combustion?

10. Energy Conversions in Technological Systems
Our society depends on the conversion of other forms of energy into electrical energy.
To produce electricity , a number of different means have been developed to convert less useful (at least to us) forms of energy to electricity.
Try to figure out what form of energy is being transformed into electricity in the following three slides and how it occurs.

14. Nuclear Energy Conversions
E = mc2
The most famous formula in physics states that even matter and energy can be converted from one form to another.
Energy is generated from nuclear reactions because the products of nuclear fission and fusion are slightly lighter then the reactants. This lost mass is converted into energy.

15. Nuclear Weapons
Although the main use of nuclear energy is in power generation, there is still approximately 10,000 nuclear warheads on the Earth.
The following video clip is from some of the early American atomic tests to study the effects of an atom bomb on a town and on the troops deployed near it. I’m serious, you can’t make this stuff up!

16. Solar Energy Conversions
The newest form of solar energy conversion is the direct transformation of light into electricity.
The image to the right is a solar cell.

17. Fuel Cells
Fuel Cells convert chemical energy directly into electrical energy.
Hydrogen and Oxygen are reacted together to form water and heat as byproducts No greenhouse gas emissions.
Nearly every car manufacturer in the world is trying to develop an affordable fuel-celled vehicle.

18. Practice: Check and Reflect: p195 Section 2 Review: p197
Energy Conversions
Check and Reflect: p195
Questions 8, 9 and 10
Energy Calculations
Section 2 Review: p197
Questions 20 – 23 and 25
These are great review
questions for Energy