* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Thermochemistry ch 16 energy diagrams phase
Public schemes for energy efficient refurbishment wikipedia , lookup
Regenerative brake wikipedia , lookup
Energy Charter Treaty wikipedia , lookup
Compressed air energy storage wikipedia , lookup
Energy storage wikipedia , lookup
World energy consumption wikipedia , lookup
Low-Income Home Energy Assistance Program wikipedia , lookup
International Energy Agency wikipedia , lookup
Zero-energy building wikipedia , lookup
Cogeneration wikipedia , lookup
Low-carbon economy wikipedia , lookup
Energy efficiency in transport wikipedia , lookup
Energy returned on energy invested wikipedia , lookup
Energy policy of Finland wikipedia , lookup
Distributed generation wikipedia , lookup
Alternative energy wikipedia , lookup
Energy harvesting wikipedia , lookup
Negawatt power wikipedia , lookup
Energy in the United Kingdom wikipedia , lookup
Environmental impact of electricity generation wikipedia , lookup
Energy policy of the European Union wikipedia , lookup
Internal energy wikipedia , lookup
Gibbs free energy wikipedia , lookup
Energy Independence and Security Act of 2007 wikipedia , lookup
Energy efficiency in British housing wikipedia , lookup
ENERGY AND CHEMICAL CHANGE CH. 16 •Energy is the ability to do work or produce heat and is found in two forms •potential energy is energy due to the composition of the substance •kinetic energy is the energy of motion (1/2 mv2) Law of Conservation of Energy • Law of conservation of energy: Energy can be converted from one form to another, but cannot be created nor destroyed Energy and units • Chemical potential energy often releases heat or needs heat • Review- kinetic energy is the energy of motion • Measuring in heat is done using units called Joules. • One Joule is = 0.2390 calories • One calorie = 4.184 Joules • One Calorie = 1000 calories (note the capital C) = 1 kcal Units and math • Measuring in heat is done using units called Joules. • One Joule is = 0.2390 calories • One calorie = 4.184 Joules • One Calorie = 1000 calories (note the capital C) = 1 kcal • How many Joules are in a bowl of breakfast cereal and milk which contain 340 Calories? Specific Heat • Specific heat is the amount of energy required to raise the temperature of one gram of a substance one degree Celsius • specific heat is measured in J/goC • specific varies based on the substance that is being measured • water has one of the highest specific heats • metals have lower specific heats (it heats up quickly) Energy Diagram for Water 100 oC __ D C 0oC __ B -20 oC A Energy increase ____________________>>> E Key to energy diagram for water • • • • • A = Ice heating ( 1 state of matter) S only B = Ice melting (2 states of matter – S and L C = Water heating ( 1 state of matter) L only D = Water boiling (2 states of matter) L and V E = Water vapor boiling (1 state of matter) V only Calculations for specific heat can only be used when the temperature changes (A, C, E) Specific Heat • To calculate heat absorbed or released by a substance: • q = m cp DT • • • • q = heat absorbed or released (heat = temp) cp = the specific heat of the substance m = mass of the sample in grams DT = change in temperature in oC or Tfinal - Tinitial Specific Heat Math • If the temperature of 34.4 g of ethanol has been raised from 25.0oC to 78.8oC how much heat has been absorbed by the ethanol? • What if this sample were cooled from 78.8oC to 25.0oC? Energy diagram for exothermic reaction Reactants Activation energy – Minimum amount of energy _ _ _ _ _ _ _ _ required to start the reaction DH is negative DH – The change in energy from reactants to products _ _ _ _ _ _ _ _ Products Time (increasing) Energy Diagram of an endothermic reaction An endothermic reactions has a higher activation energy than an exothermic reaction _ _ _ _ _ _ _ _ _products Activation energy +DH Reactants _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Energy increases DH is positive The effect of a catalyst on a chemical reaction A catalyst lowers the activation energy and shortens the path of a reaction A catalyst speeds the rate of reaction