Energy

Energy

DefinitionEnergy is the ability to do workWork is done on an object whenever a force (push or pull) moves an object through a distanceWork = Force x Distance

Forms of EnergyMechanical energy any energy possessed by macroscopic (visible) objectsTwo kinds of mechanical energyKinetic EnergyPotential EnergyPotential EnergyStored energy that is available to do work at a later time

Kinetic EnergyEnergy of motion

Heat is a form of Kinetic EnergyUnit of EnergyJoule (J)Unit used to be the calorie (cal)1 cal = 4.19 JHow many joules is 1500 calories?How many calories is 36 J?Conservation of EnergyWhatever changes occur in energy from one type to another, the total amount of energy remains constantEnergy cannot be created or destroyed

Equivalence of Mass and EnergyEinstein found that matter and energy are relatedWhenever there is a decrease in energy in a system, there is an increase in massWhenever mass increases, energy decreases

New Conservation LawOld conservation of matter and energy laws were combinedLaw of Conservation of Mass and Energy the total of mass and energy will remain constant in any reaction

Energy in ReactionsIn every change, there is a change in energyEnergy change usually more noticeable in chemical changesExothermicIf reactants have more chemical energy than the products, then energy must be lost in reactionThis release in heat energy causes the substances to become hotChemical reactions that release heat are called EXOTHERMICEndothermic ReactionsIf products have more chemical energy than reactants, energy must be absorbedThe absorption of heat causes substances to feel cold This is called an ENDOTHERMIC reactionActivation EnergyEven though some reactions are exothermic it may still require a little energy to start it offThis starting energy is called ACTIVATION ENERGY