Thermochemistry General Chemistry I CHM 111 Dr Erdal OnurhanSlide 1 Some Forms of Energy - Solar Energy, part of radiant energy. Solar energy comes from the Sun and is the primary source of Earth’s energy. - Thermal Energy is due to random motion of atoms and molecules. It is generally calculated from temperature measurements. Temperature is not a measure of thermal energy itself. - Chemical Energy is stored within the structural units of chemical substances. When a chemical reaction takes place, chemical energy is released, stored, or converted to other forms of energy. - Potential Energy is the energy due to the position of an object. Chemical energy can be considered to be a form of potential energy, since it is associated with the positions of atoms in the molecules. - Kinetic Energy is the energy produced by a moving object.

Thermochemistry General Chemistry I CHM 111 Dr Erdal OnurhanSlide 2 System-Boundary-Surroundings The boundary might be imaginary, as in this case, or real, as in other cases.

Thermochemistry General Chemistry I CHM 111 Dr Erdal OnurhanSlide 3 Three Types of Systems Open: energy an mass can be exchanged Closed: only energy can be exchanged Isolated: nothing is exchanged

Thermochemistry General Chemistry I CHM 111 Dr Erdal OnurhanSlide 4 An Example to State Functions – Distance vs. Displacement There are many routes between A and B. The distance covered by the coloured routes is different from one another. The displacement, however, is the same for all routes, AB. Displacement is a state function, whereas distance is not.

Thermochemistry General Chemistry I CHM 111 Dr Erdal OnurhanSlide 5 Another Example of a State Function- Volume

Thermochemistry General Chemistry I CHM 111 Dr Erdal OnurhanSlide 6 The First Law of Thermodynamics It is obvious that, energy lost by the system is absorbed by the surroundings. Since the Universe comprises both the system and the surroundings, energy is conserved in the process.

Thermochemistry General Chemistry I CHM 111 Dr Erdal OnurhanSlide 7 Sign Convention for Work and Heat

Thermochemistry General Chemistry I CHM 111 Dr Erdal OnurhanSlide 8 Expansion of a Gas in a Cylinder Initial StateFinal State

Thermochemistry General Chemistry I CHM 111 Dr Erdal OnurhanSlide 9 Bomb Calorimeter The thermometer is used to determine  t of the reaction. q cal is calculated from

Thermochemistry General Chemistry I CHM 111 Dr Erdal OnurhanSlide 10 An Open Calorimeter The thermometer is used to determine  t of the reaction. q is calculated from