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?