Exothermic or Endothermic

[Labdi]

How do you tell if a chemical equation is endothermic or exothermic

[Sine]

How do you tell if a chemical equation is endothermic or exothermic

have a look at the ∆H value.
Endothermic: ∆H > 0
Exothermic: ∆H < 0

If that value is not given you'll have to look deeper into the question and determine whether energy is an input or is released as a result of the reaction.

[Bri MT]

There's a few things you need to remember
- the delta H value (positive = endothermic, negative = exothermic)
- interpet energy diagrams (do reactants or products have more energy)
- the definitions

Edit: fixed typos

[Yertle the Turtle]

I'll just add an even simpler break-down:
An exothermic reaction is one that gives off heat, while an endothermic reaction takes heat from the environment. When talking about delta H, or change in enthalpy values, it is talking about the change in total chemical energy. Since an exothermic reaction gives off energy, its reactants lose energy as they react to become the products, so its delta H or change in enthalpy will be a negative number. In an endothermic reaction, the system of the chemicals used increase in energy as they take it from the surroundings, so its delta H will be positive since it has increased in energy.