Energy• Chapter 16.1

• As the roller coaster zooms up and down the track, the energy changes btwn kinetic and potential energy.

Energy

• Energy comes in many different forms:– potential energy– kinetic energy– solar energy– nuclear energy

Uses of Energy

• We use energy everyday:– to cook– run vehicles– keep buildings warm/cool– communicate– to run the miniature factories (cells) in our

bodies

• What is energy?

Vocabulary Word

• energy: the ability to do work or produce heat

• kinetic energy (KE = 1/2mv2) energy of motion

• potential energy (GPE = mgh) energy of position or composition

Energy is Conserved

• As water runs through the turbines of the hydroelectric plant, some of the potential energy is converted into electrical energy

Energy is Conserved

• As wood burns in a fire, some of its potential energy is released as heat

Energy is Conserved

• Energy is always changing forms, but the total amount of energy does NOT change.

• Energy is conserved.

Vocabulary Word

• Law of conservation of energy: in any chemical reaction or physical process energy is neither created nor destroyed (though it may change from one form to another).

Chemical Potential Energy

• Chemical potential energy is energy stored in a substance because of its composition (position of its electrons).

• octane (C8H18) is a component of gasoline

Chemical Potential Energy

• potential energy in octane is from the arrangement and strength of the bonds

• as octane burns, some of the energy is converted to work to move the pistons and some is converted to heat.

Vocabulary Word

• heat (q): energy flows from a warmer object to a cooler object

Heat

• The warmer object gets cooler

• The cooler object gets warmer

• They will both continue to transfer heat until both reach the same temperature

Vocabulary Word

• calorie: the amount of heat required to increase the temperature of pure water by 1oC

• Calorie: nutritional Calorie is equal to 1000 calories or 1kcal

Vocabulary Word

• joule: the SI unit for heat. 1 joule is equal to 0.2390 calories. 1 calorie is equal to 4.184 joules

Specific Heat

• Since 1 calorie (or 4.184 joules) is the amount of heat to increase the temperature of water by 1oC, the specific heat of water is 4.184 joules

Specific Heat

• Different substances have different specific heats

• Some substances require less energy to heat up (gold) and others require a lot (water)

Water

• Water has a very high specific heat.

• Large bodies of water (lakes, oceans...) can absorb and release large amounts of heat, that’s why the climate near a large body of water is more stable.

Vocabulary Word

• specific heat: the amount of heat required to raise the temperature of 1 gram of a substance by 1oC

Heat Absorbed or Released

• The amount of heat absorbed or released by a substance can be calculated using the following formula:q = c x m x T

heat = specific heat x mass in grams x change in temperature

Energy

• The sun is an inexhaustible source of energy.

• Why can’t the solar energy meet all our energy needs?

Solar Energy

• Why can’t the solar energy meet all our energy needs?– only available during the day– must be able to store (solar ponds)– sodium sulfate decahydrate pools

(dissolve/recrystalize)– photovoltic cells

Photovoltic Cells

• convert solar energy directly into electricity