Energy

Just What Is It

How Can We Define Energy

The capacity to do workOr the ability to cause a change to occur

What Are the Types of Energy?ElectricalChemicalHeatSolar

SoundGravitationalMagneticKinetic energy

Law of Conservation of EnergyEnergy can neither be created or

destroyedEnergy is a quantity that can be stored in

fieldsEnergy can be transfer from one field to

another with no loss of energyThe energy lost in one area will lead to an

increase in heat in another areaThe only problem is that the energy is not

always transferred into energy that you wish

What About in a Car

What does the energy start out as?Chemical energyWhat type of energy do we wish to get

out?Kinetic energyMost of the energy from gas get

transfer to what type of energyHeat

What Is Heat?

The warmer an object is the more the particles move

Temperature is the measurement of the kinetic energy of the particles

No such thing as cold scientifically- just the absence of heat

Energy Transfers Involving HeatExothermic

An event when heat energy is lost to the environment

Examples; Fire and steam condensing

Energy Transfers Involving HeatEndothermic

An event in which heat energy is removed from the environment Energy is taken in

Examples ice melting An ice pack

Why if endothermic reactions take in heat do they feel coldWhat happens to the energy?

Heat Potential EnergyHeat potential energy is measured in

calories; CA calorie is defined as the amount of heat

needed to raise the temperature of 1 gram of water 1 degree C

How much energy is need to heat 10 grams of water from 20C to 30C?

The calories listed on nutrient labels are kilocalories, C

Specific Heat CapacityEvery substance has its own ability to absorb

heatWater’s specific heat is 1c/gIs this a physical or chemical property?Specific heat is often listed as j/gc

J joule where 1 cal = 4.184 joules

Specific Heat CapacitiesSpecific Heat Capacity is a physical property

of a substanceThe specific heat capacity changes depending

on the phase of matterHeat capacity of ice 2.1J/gCHeat capacity of water 4.184J/gCHeat capacity of steam 1.7J/gC

Specific HeatsAl .9 J/g/CCu .385J/g/CGold .129J/CFe .449J/gCWater 4.184 J/gc

Calculating HeatThe heat needed to change the temperature

of an object can be easily calculated by this formulaQ= mcΔT

Q = heat gained or lost m = mass c = specific heat ΔT = change in temperature

Warming IceHow much heat is needed to heat an ice cube

with a mass of 10 grams of from -10C to 0C?Heat= mcDTHeat = 10g (2.1j/gC) 10CHeat = 210JNot the same for all ice cubes

Phase ChangesThe particles of a substance change energy

when a phase change occursIt can gain energy What happens to the temperature of a

substance as it gains energy

Names of Phase ChangesSolid to liquid

MeltingLiquid to gas

EvaporationSolid to gas

Sublimation

Liquid to solidFreezing

Gas to liquidCondensation

Gas to SolidDeposition

What happened to D.W.’s Snowball?D.W. saved a snowball in

the back of the freezer.She checked on it

regularlyOne day she looked and

it was goneWhat happened?Water will sublime

Solid to gas very slowly

Heat of FusionHeat of fusion is the amount of heat needed

to turn 1 gram of a solid into a liquidFor ice 335j/gCesium 15.7j/gMagnesium 372j/g

Heat of VaporizationHeat needed to turn 1 gram of a substance

from liquid to a gasWater 2260 j/gOxygen 213 j/g Aluminum 10,540j/g

Interesting Fact to RememberThe temperature is constant during a phase

changeWater will stay at 0C until all the ice is meltedWater will stay at 100C until all the water is

boiled away

Temperature Vs Heat Graphs

Ice

Melting

Water

Boiling

Steam

Calculating Heat AddedWith 10 Grams H20

Starting at –10C

210J

3350J10gX335j/g

4184J

22,600J10g x 2260J/g

Ending at 110C

170J

Total Heat Needed66,004J

Heat of CombustionHeat of combustion lists the amount of

energy given off when something burnsThe heat of combustion can be calculated

easily for many substancesThe nutrient labels are based upon the heat

of combustion of the ingredients

Heat of CombustionThe heat given off when

burning 1 gram of a substance

Determined using a calorimeter