5.1 Calorimetry

thermal energy

total energy of motion of all the tiny particles inside an object

chemical system

specific part of the universe that we are focusing on when studying how substances change and interact with each other

exothermic definition

heat is released into surroundings

change in H < 0

endothermic definition

absorb heat from surroundings

change in H > 0

open system

can exchange both energy and matter with its surroundings

(pot of boiling water without a lid; steam (matter) escapes, and heat (energy) is also lost to the air)

closed system

can exchange energy but not matter with its surroundings

(pot of boiling water with a lid; heat (energy) can still go in or out, but the water (matter) cannot escape)

isolated system

cannot exchange either energy or matter with its surroundings

thermochemistry

study of how heat and energy are involved in chemical reactions and physical changes

physical change

overcome IMF and particles remain unchanged

10⁰-10² KJ/mol

state changes

chemical change

overcome electronic structure + chem bonds

10²-10⁴ KJ/mol

eg. burning wood, neutralization reaction

nuclear change

over come strong force

10¹⁰-10¹² KJ/mol

eg. nuclear fission, radioactive decay

exothermic examples

• condensation

• candle flame

• heat packs

• burning sugar

• making molecule in the gas phase

• rusting

• making ice

• forming ion pairs

• soduim sulfite + bleach

endothermic examples

• melting ice

• frost to water vapor

• evaporation

• bond breaking

• cold packs

• melting salts

• cooking