1. Heat/Temperature & Systems
330_06_04 Energy: Enthalpy of Chemical Reactions

2. Terms & Concepts
Heat:
the transfer of thermal energy between two bodies that are at different temperatures.
thermochemistry = the study of heat change in in chemical reactions
measured as “heat flow”
 temperature the property of matter which reflects the quantity of energy of motion of the component particles.
Heat versus Temperature:
The water in the bathtub may have more heat, but the water in the cup is hotter.

3. Enthalpy of Chemical Reactions
Chemical reactions involving heat:
2H2(g) + O2(g)  2H2O(l) + energy
State symbols are very important in thermochemistry.
Identify the parts:
The reacting mixture (H2,O2, & H2O molecules),
system (open, closed, isolated), and
surroundings (the rest of the universe)

4. Two Types of Processes exothermic reaction
transfers heat from the system to the surroundings.
2H2(g) + O2(g)  2H2O(l) + energy
endothermic reaction
transfers heat from the surroundings to the system.
H2O(l) + energy  H2O(g)
330_06_02 Energy: Chemical Reactions

5. Terms & Concepts Thermochemistry:
The study of heat change in chemical reactions
System:
the specific part of the universe that is of interest in the study
allows the transfer of energy (heat) and mass
allows the transfer of energy (heat) but not mass
does not allow energy or mass transfer
open
closed
isolated

6. Fin
Energy