Exothermic and Endothermic
Reactions
Aims
We are learning to:
• Know that energy changes can be
measured in chemical reactions.
Keywords
Exothermic, endothermic, energy.
Learning Outcomes
Must: State a definition for exothermic and
endothermic.
Should: Recognise an exothermic and
endothermic reaction from a practical.
Could : Explain the difference between
endothermic and exothermic.
Reaction Videos
Thermite Reaction.
•After adding one or more catalysts, iron oxide
(rust) and aluminum react to produce elemental iron
and aluminum oxide.
•So much heat is produced in this reaction that the
iron becomes a liquid. The heat is so intense that
the molten iron can be used to weld railroad tracks
together.
www.middleschoolchemistry.com/multimedia/chapter6/lesson7#thermite
Reaction Videos
Nitrogen Triiodide Reaction
•This is a decomposition reaction where nitrogen
triiodide decomposes into nitrogen gas and purple
iodine vapor.
•Nitrogen triiodide crystals are so unstable that just a
light touch will cause them to rapidly decompose
generating a great deal of heat.
www.middleschoolchemistry.com/multimedia/chapter6/lesson7#nitrogen_trii
odide
Reaction Videos
White Phosphorous Reaction.
White phosphorous is dissolved in a solvent and
spread on a piece of paper. When the solvent
evaporates, the phosphorous reacts with oxygen in
the air in a combustion reaction.
www.middleschoolchemistry.com/multimedia/chapter6/lesson7#white_phos
phorous
Endothermic Reactions
• When the temperature of a chemical reaction
decreases, the reaction is called an endothermic
reaction.
• The first part of the word, endo, means in or into and
thermic has to do with heat or energy.
• Endothermic reaction means that more energy
goes into making the reaction happen than is
released by the reaction. This leaves the reaction
mixture at a lower temperature
Exothermic Reactions
• In an exothermic reaction it takes less
energy to break the bonds of the reactants
than is released when the bonds in the
products are formed.
• In an exothermic reaction, the temperature
goes up.
Temperature Experiments
Carry out the experiments on the Weebly to
investigate whether they are
Exothermic or Endothermic
Chemical reactions where HEAT… Chemical reactions where HEAT…
Is transferred to the
surroundings…
Is transferred from the
surroundings …
Indicated by a RISE in
temperature
Indicated by a FALL in
temperature
Conclusion
Write in a sentence which reactions are
endothermic and which are exothermic.
Break bonds which
releases heat energy.
Need to make bonds so
take in energy, reducing
the temperature.
Conclusion Questions