Confusing “por” with “para” in Spanish is like confusing a plate of spaghetti with one of fettuccine: they are similar, but different.
Por and para are prepositions (connectors between the parts of a sentence) that fulfill very specific functions in the language and, once you learn to differentiate them, you will not confuse them again.
On the one hand, we have a por, a preposition whose main function is to express the cause or reason for an action; and, on the other hand, we have a para, which serves to indicate the purpose or purpose of an action.
Thus, a simple way to determine if you should use por or para is to determine if what you are trying to express is the cause of what is happening, or if it is the purpose.
In addition to serving as a connector to express the cause of an action, por is used to express both measures of time, space or place, indeterminate:
To indicate the medium or channel through which something happens, or a place of passage:
To report a distribution or periodicity measure:
To express an exchange:
Finally, por is used to introduce the agent complement in a passive sentence (don’t worry, it’s simpler than it seems):
In turn, the preposition para fulfills other important functions, such as expressing the recipient of an action or an object:
To indicate a time frame:
And to express the issuer of an opinion:
As you can see, the functions por and para fulfill are very specific and, when in doubt, a good exercise is to pose the sentence with both prepositions to see which best expresses what is being conveyed.
Many times, it can be complicated to define the difference between cause and purpose, but it is as simple as the following:
The reason “por” an action or situation is the cause; while the “para” is the purpose.