# Is condensing water vapor an exothermic process or an endo process?

Nov 21, 2016

#### Answer:

Well condensation is the reverse of vaporization, so it is clearly exothermic.

#### Explanation:

When we boil water, we put heat into the system:

${H}_{2} O \left(l\right) + \Delta \rightarrow {H}_{2} O \left(g\right)$

Now this physical process as written is clearly ENDOTHERMIC. And it makes sense intuitively.

Given this, the reverse process must clearly be EXOTHERMIC:

${H}_{2} O \left(g\right) \rightarrow {H}_{2} O \left(l\right) + \Delta$

When you include the $\Delta$ symbol in your reactions, this can help to rationalize the direction of energy transfer, and whether a process is exothermic etc.