1. Heat changes in reactions
5.4.0 Thermochemistry
Heat changes in reactions

2. Endothermic Reactions
Exothermic Reactions
Produce heat [give out heat]
Feel hot to the touch
 H is negative (-)
Endothermic Reactions
Use heat [take in heat]
Feel cold to the touch
 H is positive (+)

3. Reactions usually result in a change of temperature.
Temperature will rise if heat is produced
Temperature will fall if heat is used

4. Changes of Phase [state]
These add or subtract from actual heat change values.
Melting and Evaporation use heat
they have a positive value [endothermic]
Condensing and Solidifying release heat
they have a negative value [exothermic]

5. Test What does exothermic mean? [1]
How can you tell a reaction is exothermic? [2]
Give an example of an exothermic reaction. [2]
What does endothermic mean? [1]
How can you tell a reaction is enothermic? [2]
Give an example of an endothermic reaction. [2]
What does ΔH mean?
Give the sign of ΔH for exothermic and endothermic reactions.
What is ΔH for solid to liquid?

6. Test What does exothermic mean? [1] gives out heat
How can you tell a reaction is exothermic? [2] feels / hot
Give an example of an exothermic reaction. [2] burning/coal
What does endothermic mean? [1] takes in heat
How can you tell a reaction is endothermic? [2] feels / cold
Give an example of an endothermic reaction. [3] dissolving / sherbet [or ammonium chloride] / in water
What does ΔH mean? [2] Heat change
Give the sign of ΔH for exothermic and endothermic reactions. [2] –ve and + ve
What is ΔH for solid to liquid? [1] -ve
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