C5 - chemical energetics (exo. & endo.)
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define exothermic reaction
-reaction that transfers heat energy to surrounding so temp. goes up
Explain an exothermic reaction in terms of bond breaking and bond making
-Less energy is absorbed to break bonds than energy released to make bonds
what type of reaction is neutralization reaction
exothermic
define endothermic reaction
-reaction that absorbs heat energy from the surrounding so temp. goes down
Explain an endothermic reaction in terms of bond breaking and bond making
-more energy is absorbed to break bonds than energy released to make bonds
what must you do to break and make bonds
-break = absorb energy -make = release energy
what is in the system
reactants & porducts
what is system & surr. in energy
-system = chemical energy -surr. = heat energy
what happens to system & surr. in exo.
-system gives heat energy to surr. -surr. heats up
what happens to system & surr. in exdo.
-surr. gives heat energy to system -system. heats up
symbol for activation energy
-Ea (a is subscript)
what do you call thermal energy & its symbol
-Enthalpy -H
define Enthalpy change
-The difference between the energy required to break bonds and the energy released to make bonds
what is ( - ) ve & ( + ) ve
-( - ) ve = negative -( + ) ve = positive
how do you draw a graph for exo. reaction
-Enthalpy on side -reactants is higher than products -reactants to products line is ΔH = -ve -activation energy curve -Ea is at peak of activation energy line to reactants line -left is absorb E, right is release E -arrows must touch -ΔH is arrow down, Ea is arrow up
how do you draw a graph for endo. reaction
-Enthalpy on side -products is higher than reactants -reactants to products line is ΔH = +ve -activation energy curve -Ea is at peak of activation energy line to reactants line -left is absorb E, right is release E -arrows must touch -both arrows face up