Energy Changes in Chemical Reactions Flashcards
Define exothermic
Energy is transferred from stores of energy in chemical bonds to the surroundings
Define endothermic
Energy is transferred from the surroundings to stores of energy in chemical bonds
In a reaction profile, which way would the arrow point for an exothermic reaction
Down (energy released)
In a reaction profile, which way would the arrow point for an endothermic reaction
Up (energy taken in)
How can you determine if a reaction is endothermic or exothermic using temperature?
Exothermic - Temperature increases
Endothermic - Temperature decreases
Name 2 exothermic reactions
Neutralisation (reaction between an acid and a base)
Displacement (reaction between a metal, and a compound of less reactive metal OR between a halogen and a compound of a less reactive halogen)
How can you add activation energy to a reaction profile?
See notes
What happens during endothermic reactions, in terms of bonds?
Energy is transferred to reactants to break their bonds, so bond breaking is endothermic
What happens during exothermic reactions, in terms of bonds?
Energy is transferred to the surroundings as bonds form, so bond making is exothermic
How do you calculate energy changes in reactions?
Energy of bonds in - Energy of bonds out
If the answer is negative, the reaction is exothermic as bonds are being made
If the answer is positive, the reaction is endothermic as bonds are being broken
What happens, in terms of temperature, during exothermic reactions?
More heat energy is released in forming bonds in the products than is required in breaking bonds in the reactants (so, temperature increases)
What happens, in terms of temperature, during endothermic reactions?
Less heat energy is released in forming bonds in the products than is required in breaking bonds in the reactants (so, temperature decreases)
