Just What Is It

How Can We Define Energy The capacity to do work Or the ability to cause a change to occur

What Are the Types of Energy? Electrical Chemical Heat Solar Sound Gravitational Magnetic Kinetic energy

Law of Conservation of Energy Energy can neither be created or destroyed Energy is a quantity that can be stored in fields Energy can be transfer from one field to another with no loss of energy The 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 energy What type of energy do we wish to get out? Kinetic energy Most of the energy from gas get transfer to what type of energy Heat

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 Heat Exothermic An event when heat energy is lost to the environment Examples; Fire and steam condensing

Energy Transfers Involving Heat Endothermic 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 cold What happens to the energy?

Heat Potential Energy Heat potential energy is measured in calories; C A 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 Capacity Every substance has its own ability to absorb heat Water’s specific heat is 1 j/gc Is this a physical or chemical property? Specific heat is often listed as j/gc J joule where 1 cal = joules

Specific Heat Capacities Specific Heat Capacity is a physical property of a substance The specific heat capacity changes depending on the phase of matter Heat capacity of ice 2.1J/gC Heat capacity of water 4.184J/gC Heat capacity of steam 1.7J/gC

Specific Heats Al.9 J/g/C Cu.385J/g/C Gold.129J/C Fe.449J/gC Water J/gc

Calculating Heat The heat needed to change the temperature of an object can be easily calculated by this formula Q= mcΔT Q = heat gained or lost m = mass c = specific heat ΔT = change in temperature

Warming Ice How much heat is needed to heat an ice cube with a mass of 10 grams of from -10C to 0C? Heat= mc  T Heat = 10g (2.1j/gC) 10C Heat = 210J Not the same for all ice cubes

Heat of Fusion Heat of fusion is the amount of heat needed to turn 1 gram of a solid into a liquid For ice 335j/g Cesium 15.7j/g Magnesium 372j/g

Heat of Vaporization Heat needed to turn 1 gram of a substance from liquid to a gas Water 2260 j/g Oxygen 213 j/g Aluminum 10,540j/g

Interesting Fact to Remember The temperature is constant during a phase change Water will stay at 0C until all the ice is melted Water will stay at 100C until all the water is boiled away

Temperature Vs Heat Graphs Ice Melting Water Boiling Steam

Calculating Heat Added With 10 Grams H 2 0 Starting at –10C 210J 3350J 10gX335j/g 4184J 22,600J 10g x 2260J/g Ending at 110C 170J Total Heat Needed 66,004J

Heat of Combustion Heat of combustion lists the amount of energy given off when something burns The heat of combustion can be calculated easily for many substances The nutrient labels are based upon the heat of combustion of the ingredients

Heat of Combustion The heat given off when burning 1 gram of a substance Determined using a calorimeter