1. Energy
Ch. 15

2. Forms of Energy
Energy is the ability or capacity of any physical system to do work
Work is done by forces
Kinetic Energy – energy in motion
Potential Energy – energy at rest or stored energy
Any form of energy can be converted into another form

3. Types of Energy Thermal – a.k.a. heat energy
Electrical – from forces of the electrical charges of subatomic particles (p & e)
Light – radiant energy (makes up the electromagnetic spectrum)
Nuclear – stored in the bonds of an atom’s nucleus (given off by breaking or creating those bonds)

4. Transformation Changing one form of energy into another
Ex: Hydroelectric dams use generators to transform the kinetic mechanical energy of falling water into kinetic electrical energy

5. Law of Conservation of Energy
Energy is neither created nor destroyed, it is changed from one form to another
In a closed system, the amount of energy remains constant. (Ex: the cells in your body)
In an open systems, energy is lost to heat and other transformations.
Explained by James Prescott Joule

6. Chemical & Mechanical
Chemical potential energy is stored in the nutrients in food – your cells transform it into kinetic energy
Some of this energy is changed into mechanical energy (Ex: when your brain sends a signal to move your muscle)
Changes into Mechanical Energy

7. When you speak – mechanical. energy in your breath is
When you speak – mechanical energy in your breath is changed into sound energy by your vocal chords
Nerve cells transform chemical energy into electrical energy that transmits nerve signals to parts of the body
When you eat, chemical energy from food is turned into thermal energy (heat energy)

8. Other animals do this too…
Electric eels – use electrical energy to stun their prey or keep predators away with powerful shocks
Fireflies – transform chemical energy into light energy

9. Other uses… Thermal energy keeps us warm when its cold outside
When a match is struck, friction transforms mechanical energy into enough thermal energy to ignite the match
Chemical energy stored in the wood of the matchstick changes into more thermal energy as the wood burns

10. Mass related to energy…
The more mass an object has, the more energy it can absorb
Ex: The ocean’s huge mass absorbs a tremendous amount of heat during the summer & releases it during the winter – this helps keep coastal climates more moderate during both seasons

11. Lava lamps…
Transform electrical energy into light energy, mechanical energy, and thermal energy.
These transformations happen all day every day, in our bodies and all around us

12. Mechanical Energy…2 parts
Kinetic energy
Potential energy
ME = KE + PE

13. Kinetic Energy Energy in motion KE = ½ • m • v2
KE = ½ mass • velocity2

14. Figure it out…
What is the K.E. of a 10 kg mass moving w/ a velocity of 10 m/s?
KE=½ mv2
KE=½ (10 kg) (10 m/s)2
KE=500 kg•m2/s2
1 kg•m2/s2 =1 J
KE=500 J
What if you double the mass?
What if you double the velocity?

15. Potential Energy Energy at rest = potential to move PEg = m • g • h
g = gravitational acceleration = ?
PEg = mass • 9.8 m/s2 • height
Always measured in reference to the height
Different types of potential energy
Involves mass, gravity, & height

16. Figure it out… What is the PE of a 10 kg rock on top of a 100 m hill?
PEg = m g h
PEg = (10 kg) (9.8 m/s2) (100 m)
PEg = 9800 kg • m/s2 • m
PEg = 9800 J

17. Reminder ME = KE + PE N = kg • m/s2 J = N • m
Acceleration due to Gravity = 9.8 m/s2

18. Ch 14 & 15 Review Work, Power, Energy
Formulas
W = F • d
P = W / t
PEg = m • g • h
KE = ½ • m • v2

19. Facts
IMA vs. AMA
Why?
Newton’s laws of motion
1st
2nd
3rd

20. .

21. More facts Work is done only if there is movement
How do we arrive at a number for amu of an element?
Covalent vs. Ionic bonds
How do they form? Which ones pair up?
Co = NM & NM I = M & NM

22. More facts Law of Conservation of Energy ?
Chemical change vs. Physical Change