Energy in Chemistry

What is Energy I cant define it, but I know it when I see it. - Potter Stewart, Supreme Court Justice, (when asked to define pornography) Examples of forms of energy – Heat – Chemical Bonds – Kinetic energy – Electricity – Pressure

Conservation of Energy Energy is not created or destroyed, just converted from one form to another Take a small bit of sunlight from the sun – Is converted to chemical energy through photosynthesis – Is converted to coal through time and decay – Is burned in a power plant and converted to heat – Heat is used to make steam and run a generator – The electricity produced runs a light bulb – And then converted to heat

Temperature Atoms and molecules are in constant motion The measure of the kinetic energy of that motion is temperature Temperature is an average – some particles have greater energy and some have less There is greater variation in the energies of gas molecules than for liquids and solids

Heat Heat is thermal energy, measured in joules or calories. 1 calorie = joules A food Calorie is actually a kilocalorie, or 1000 calories Heat energy stored in matter is proportional to temperature Heat energy flows from high temperature to lower temperature

Specific Heat Specific heat is the amount of heat needed to raise the temperature of 1 gram of a substance 1 degree C Examples, with Specific Heat in J/g°C Water4.184 JOil1.900 J Air at 1 atm1.006 JGlass0.800 J Steel0.470 JGold0.129 J

Heat Equation Energy required to heat a substance is Mass times specific heat times difference in temperature in degrees C