Chapter 16Chapter 16EnergyEnergy

EnergyEnergyEnergy= ability to do work or produce heatEnergy= ability to do work or produce heat

Heat = form of energy that flows from warmer to Heat = form of energy that flows from warmer to cooler objectcooler object

James Joule was first person to connect energy James Joule was first person to connect energy and heatand heat

Joule (J) = metric unit of heat and energyJoule (J) = metric unit of heat and energy– It takes 4.184 joules to move 1 kg 1 meter in 1 It takes 4.184 joules to move 1 kg 1 meter in 1

secondsecond

Types of EnergyTypes of EnergyPotential energyPotential energy– Energy of positionEnergy of position– stored in chemical bondsstored in chemical bonds

Kinetic energyKinetic energy– Energy of motionEnergy of motion– formed when chemical formed when chemical

bonds are brokenbonds are broken

Potential EnergyPotential EnergyPotential energy is determined by type and Potential energy is determined by type and number of chemical bondsnumber of chemical bonds– Helps explain why diesel (which has more bonds) Helps explain why diesel (which has more bonds)

trucks can get same gas mileage as octane (gas) trucks can get same gas mileage as octane (gas) carscars

Law of Conservation of EnergyLaw of Conservation of EnergyEnergy is never created nor destroyed but it Energy is never created nor destroyed but it can change formscan change forms

Energy is usually lost in the form of heatEnergy is usually lost in the form of heat

Car engine converts about 37% of energy into Car engine converts about 37% of energy into movementmovement– Feel the top of the hood after drivingFeel the top of the hood after driving– Most energy is lost as heatMost energy is lost as heat

Measuring HeatMeasuring Heatcaloriecalorie– Amount of heat needed to raise the temperature of Amount of heat needed to raise the temperature of

1 gram of pure water 11 gram of pure water 1°C°C

Food Calorie = 1000 caloriesFood Calorie = 1000 calories

You need to memorize the following You need to memorize the following conversions!conversions!– 1 Calorie = 1000 calories = 1 kilocalorie1 Calorie = 1000 calories = 1 kilocalorie– 4.184 joules = 1 calorie4.184 joules = 1 calorie– 1000 joules = 1 kilojoule1000 joules = 1 kilojoule

How to solve heat problemsHow to solve heat problems

Dimensional AnalysisDimensional Analysis

-process of canceling out units-process of canceling out units

Set up all ratios with units NOT numbersSet up all ratios with units NOT numbers Plug in numbersPlug in numbers Multiply everything on the top of fractionMultiply everything on the top of fraction Multiply everything on the bottom of fractionMultiply everything on the bottom of fraction DivideDivide

1. Convert 10 calories to joules1. Convert 10 calories to joules

2. Convert 10 joules to calories2. Convert 10 joules to calories

3. Convert 3000 joules to kilojoules3. Convert 3000 joules to kilojoules

4. Convert 3000 calories to kilocalories4. Convert 3000 calories to kilocalories

5. Convert 3000 calories to Calories5. Convert 3000 calories to Calories

6. Convert 3000 calories to kilojoules6. Convert 3000 calories to kilojoules

7. Convert 3000 joules to kilocalories7. Convert 3000 joules to kilocalories

8. Convert 3000 joules to Calories8. Convert 3000 joules to Calories

9. Convert 10 kilojoules to kilocalories9. Convert 10 kilojoules to kilocalories

10. Convert 10 Calories to kilojoules10. Convert 10 Calories to kilojoules

11. Convert 3000 calories/minute to joules/hour 11. Convert 3000 calories/minute to joules/hour

12. Convert 10 kilojoules/minute to 12. Convert 10 kilojoules/minute to kilocalories/hourkilocalories/hour