chemical energetics

in a chemical reation broken bonds….

in a chemical reaction, bonds of reactant molecules are bring broken, while new bonds are being created with the broken reactant bonds

endothermic, bond breaking

more energy is absorbed in breaking bonds, than forming bonds

bond enthalpy

average amount of heat absorbed to break one mole of that chemical bond in the gaseous state

enthalpy (H)

a measure total heat energy in a thermodynamic system

enthalpy change (△H)

a change in total heat energy in a thermodynamic system in an object ( positive or negative

enthalpy change instrument

enthalpy change can be measured using a calorimeter

enthalpy change formula

△H = total energy of products - total energy of reactants

exothermic, bbf

more energy is released in forming bonds, than breaking bonds

bond breaking formula

△H = total energy absorbed for bond breaking - total energy released from bond breaking

if neg (exo)
if positive (endo)

requirement for bond breaking

higher energy absorbed is needed to break stronger bonds

bond enthalpy formula

△H = total energy absorbed for bond breaking - total energy released from bond forming

activation energy explained 2

for the reactants to collide successfully the particles must react with the correct orientation

2 types of enthalpy changes

exothermic reaction ( - )
endothermic reaction ( + )

exothermic reaction

loses energy in the reaction ( - )

object cools down
surroundings gets warmer

object released internal energy to surroundings

endothermic reaction

gains energy in the reaction ( + )

objects gets warmer
surroundings gets cooler

object absorbs the heat from the surroundings

activation energy

the minimum energy that is needed by the reactant particles for a chemical reaction to occur

activation energy explained

when reactant particles collide with each other to react, for the reaction to occur a certain amount of energy is required ( activation energy )

energy profile diagram

diagram that shows the energy used over time with enthalpy change (△H) and activation energy