Exothermic and Endothermic Reactions

[Bilal Ismail Ahmed 3G]

What is the difference between an exothermic and endothermic reaction in physical terms? In which one of these is the net change in energy positive and in which one is it negative?

[Jake Ney lecture 1 discussion 1F]

Endothermic reactions absorb heat or energy from the environment and therefore require an input of energy. Exothermic reactions release heat onto the environment and are signified by a negative change in enthalpy -(ΔH).

[Jennifer Cheng 2L]

You can also think of it like this:

Endothermic reactions: Reactants + Heat → Products
Since you are adding heat, there is a positive change.

Exothermic reactions: Reactants → Products + Heat
Heat is released, or "subtracted" from the reactants, so there is a negative change.

[marinah]

Another helpful component of these endo/exo-thermic reactions is with the addition of heat, what occurs to the reaction shift.
Endothermic reactions: (+enthalpy)
1) increasing temperature, shifts reaction to the right.
2) decreasing temperature, shifts reaction to the left.
Exothermic reactions: (-enthalpy)
1) increasing temperature, shifts reaction to the left.
2) decreasing temperature, shifts reaction to the right.