Thermochemistry Chapter 10 thermo #1.ppt thermo #1.ppt

Today, you will learn… The definition of energy The major types of energy The difference between temperature and heat The definition of a state function

The study of heat energy released or required THERMOCHEMISTRY The study of heat energy released or required by chemical reactions Energy is often released as heat and light. Combustion - Fuel is burned (reacts with oxygen) to produce energy. CH4(g) + 2O2(g) CO2(g) + 2H2O(l) + energy Combustion of a hydrocarbon always produces CO2 and H2O!

Energy due to position (stored energy) Kinetic energy (KE) Potential energy (PE) Energy due to motion Energy due to position (stored energy)

Symbol is T Units are in C or K Measures AVERAGE kinetic energy of the particles in a substance. Temperature Symbol is Q Units are calories (cal) or Joules (J) Measures TOTAL kinetic energy of the particles in a substance Heat

Thermal Energy Relationships If temperature increases… Thermal energy also increases Why? The kinetic energy of the particles increased If the temperature stays the same… More mass (more particles) = more thermal energy. Example: A whole pan full of boiling water would cause more damage than a drop of boiling water

Total Energy = Kinetic Energy + Potential Energy E = KE + PE Kinetic energy & potential energy are interchangeable Ball thrown upwards slows & loses kinetic energy but gains potential energy The reverse happens as it falls back to the ground

Law of Conservation of Energy : the total energy of the universe is constant and can neither be created nor destroyed; it can only be transformed. This is also known as the First Law of Thermodynamics.

internal energy, E, of a sample is the sum of all the kinetic and potential energies of all the atoms and molecules in a sample TOTAL energy of all the atoms and molecules in a sample Includes not only heat energy, but also energy in other forms (such as the energy stored in chemical bonds.)

Energy is a state function State function – depends only on initial and final conditions - independent of pathway Distance between cities is a state function… Distance you travel is not!