Science 10Aim: What is energy
AgendaScience Sizzler. Energy Notes Cont.Lunch
Next class
Energy Conversions-Energy changing from one form to another Evidence of Energy Conversion
Motion- Ex: baseball pitcher
Change in Position (gravitational potential energy)
- Ex: lifting a bookChange in Shape
- Ex: elastic bandsChange in Temperature
- Ex: cooking
Potential Energy (PE)- Stored energy
that can converted into other forms
Kinetic Energy (KE)- Energy due to
motion
Kinetic Vs. Potential Energy
Can Energy Disappear??
Energy Cannot be created or destroyed, only converted from one form to another
Energy at the beginning of a system, input energy = output energy
Law of Conservation of Energy
Sunlight Plants Plants create sugars Animals Break down sugars through respiration Create ATP Carry out life functions, and produce heat
Hydro-electric dams, Coal burning plants, Nuclear energy, solar energy, and fuel cells
Energy in Nature & Technology
1) energy may neither be created nor destroyed.2) the total amount of energy in a system remains constant over time
The Law of Conservation of Energy
Hydro-electric Dams Coal-Burning Power Stations Nuclear Power Radiation Solar Cells Fuel Cells
Energy Transfer Technologies
Hydro-electric Dams
Coal-burning Power Station
CANDU Reactor = use the splitting of an atom (fission) to fuel the reactor and make electricity
http://www.youtube.com/watch?v=jNOzh4Kwgpw(CANDU = CANada Deuterium-
Uranium reactor)
Nuclear Energy Conversions
Radiation (electromagnetic waves or as moving subatomic particles)
thermal energy heats water steam turns turbine creates mechanical energy that goes into a generator creates electrical energy
Radiation as an Energy Source
composed of 2 layers of silicon (one with phosphorus, one with boron)
When light hits the layers, it causes electrons to break free from the silicon◦phosphorus layer = becomes negative
◦boron layer = becomes positive Poles are created and electricity is made (flowing of electrons)
Solar Cells
Hydrogen fuel cells operate like a battery
Fuel Cells- Convert chemical energy in hydrogen into electrical energy
- Does not need recharging – needs fuel (water & heat) to work
- Is popular in spacecrafts
The Development of Steam Engines
A steam engine is …
….any machine that generates steam and converts the steam pressure into mechanical motion.
The First “Steam Engine” Hero of Alexandria (Greek inventor) invented the first “steam engine” sometime between 130 B.C. and 70 A.D.
It was really only a toy, since it didn’t have any practical purpose.
The First Practical Steam Engine… Were developed in the 1600’s. Designed to remove water from coal mines.
The Savery Steam Engine Thomas Savery of England built the first practical machine to pump water from coalmines.
Patented in 1698.
Very inefficient and costly to operate. Relied on atmospheric pressure to push the water out of the mine.
The Newcomen Steam Engine Designed an atmospheric engine in 1712. Big improvement from Savery’s engine. - Didn’t have to open valves manually.
Used atmospheric pressure to push the piston down Also used atmospheric pressure to pump water out of mines. Engine wore out quickly due to constant heating and cooling of parts.
The ‘Double Acting’ Steam Engine Invented by James Watt in 1796 Was the model for all steam engines for years to come.
The ‘Double Acting’ Steam EngineSteam condensed by a spray of water in a separate chamber. This caused engine parts to always be hot, so they lasted longer.
Designed a system of gears and levers so the piston could turn a wheel. This provided power for many industries.
Steam engines and the Industrial Revolution
Watt’s steam engine was responsible for the rapid development of the Industrial Revolution, which began in the late 1700’s.
Powered machines in flourmills, saw mills,
and textile factories.
Steam powered tractors were used to produce food for the growing populations.
Steam powered locomotives and paddle-wheel steamboats were developed to transport people and supplies
Steam TurbinesDesigned in 1884
Steam-Turbine Engines are used to power giant ocean liners and cruise ships.
Steam turbine engines do not use pistons; they use curved blades similar to fan blades.
Modern turbines use several rotors and several sets of stationary blades.
Theories of Heat
What is heat??
Early Theories of HeatTheory of the 4
ElementsApprox. 450 BC
All matter consists of some combination of earth, air, fire, and water
Many objects contain fire, and when they burn fire is released
Early Theories of HeatPhlogiston Theory
Early 1700s Substances that burn
contain an invisible liquid called Phlogiston that flows out when burned
Early Theories of HeatCaloric Theory
Late 1700s Caloric (heat) is a mass-less
substances found in all substances Caloric flows from warmer to cooler
objects 1 Calorie = amount of Caloric
needed to increase the temperature of 1 g of water 1oC
Modern Theories of Heat
Count Rumford’s Hypothesis1780s
While making a cannon, the tools and metal became very hot. This didn’t make sense with the Caloric Theory
Rumford suggested ‘caloric’ (the mass-less substance) did not exist and that the mechanical energy beingexerted on the cannon and tools was being converted to heat
Julius Mayer’s Hypothesis1840s
DoctorSuggested heat was related to energy Proposed that energy from food was used to do physical work and to heat the bodyBecause he wasn’t schooled in math/physics, his ideas weren’t acceptedDespite his work, James Joule was given credit
for discovering the mechanical equivalent of heat
James JouleLate 1800s
Conducted numerous experiments to determine the mechanical equivalent of
heat
Measured the force that gravity exerts on the weight and the distance the weight fell
From this he determined the work done on the water and related it to temperature
The Kinetic-Molecular Theory
The molecules of a substance are in constant, random motion. The faster they move, the warmer the substance gets
Energy and WorkWork = The Transfer of Mechanical Energy from One Object to Another
Work: Is done when a force is applied over a distance
W = F x Δd Joule (J) Newton (N) Distance (m)
Force = A Push or Pull on an Object
You exert a force of 25 N on your textbook while lifting it a height of 1.4 m to put it on the shelf. How much work did you do on the textbook?
If you push on a wall as hard as you can and it does not move, do you do any work on it?