6A Introduction to enthalpy and enthalpy change Flashcards
what are the two components that make up chemical energy and their deffinition
- kinetic energy = measure of the motion of particles
2. potential energy = the measure of how strongly these particles interact together
what is heat energy
a portion of kinetic and potential energy in a substance that is responsible for its temperature
what is heat energy directly proportional to
the absolute temperature
what is enthalpy
a measure of the total energy of a system,
what is the enthalpy change of a process
is the heat energy that is transferred between a system and the surrounding at constant pressure
what are exothermic reactions
it is when heat energy is transferred from the system to the surroundings
what are endothermic reactions
it is where heat energy is transferred from the surroundings to the system
what are examples of exothermic reactions
- freezing of ice
- condensing of water
- (dissolving sodium hydroxide in water)
- ( dilute HCl with NaOH(aq) )
- combustion (of petrol)
what are examples of endothermic reactions
- melting ice
- evaporating water
- dissolving ammonium nitrate in water
- reaction between ethanoic acid and solid sodium hydrogencarbonate
- photosynthesis
what does the + sign mean in enthalpy change
that heat energy is being transferred from the surrounding to the system (endothermic)
what does the - sign mean in enthalpy change
that heat energy is being transferred from the system to the surroundings (exothermic)
anything that is continually heated for the reaction to take place is
is endothermic (decomposition)
what is the standard condition set by the IUPAC
100KPa and 298K
what is the standard enthalpy change of reaction
it is the enthalpy change that occurs when equation quantities of material react under standard conditions
