8 [Energetics 1] Flashcards
What are the 2 most important forms of energy?
Chemical energy
Heat energy
What is chemical energy made up of?
Kinetic energy which is a measure of the motion of particles
potential energy which is a measure of how strongly these particles interact with each other
What is heat energy?
Heat energy is the portion of the potential energy and the kinetic energy of a substance that is responsible for the temperature of a substance
The heat energy of a substance is directly proportional to its absolute temperature
What is enthalpy and enthalpy changes?
Enthalpy is a measure of the total energy of system
You cannot directly determine the enthalpy of a system but can measure the enthalpy change (delta H) that takes place during a physical or chemical reaction
The enthalpy change of a process is the heat energy that is transferred between the system and that surroundings at constant pressure
What are exothermic and endothermic reaction?
Exothermic - Where heat energy is transferred from the system to the surroundings. Exothermic reactions negative values
Endothermic - Where heat energy is transferred from the surroundings to the system Endothermic positive values
What are example of exo and endothermic reactions
Exothermic
Freezing
Condensing water vapour
Dissolve sodium hydroxide in water
Reaction between dilute hydrochloric acid and aqueous sodium hydroxide
Combustion
Endothermic
Melting ice
Evaporating water
Dissolving ammonium nitrate in water
Reaction between dilute ethanoic acid and solid sodium hydrogen carbonate
Photosynthesis
What is the system in a reaction?
The system refers to the reaction mixture. Everything outside of the system is called the surroundings
