Por qué
It serves to ask for a reason, it is used in interrogative sentences, direct and indirect. "Por" it is a preposition and "qué" is an interrogative (which is written with a tilde).
-"¿Por qué te cambiaste de trabajo?" (Interrogative direct)
-"No sé por qué ella siempre llega tarde a clases" (Interrogative indirect)
Porque
It is a causal conjunction and is used in sentences that explain the cause of the main sentence. It's equivalent to saying "Since" or "then".
-"Quiere pedir la cuenta porque no le gustó el servicio"
"Patricia no come carne porque es vegetariana"
Porque serves to answer a question entered by "Por qué".
¿Por qué es importante donar sangre? - Porque las donaciones de sangre contribuyen a salvar vidas
¿Por qué no has venido a la reunión? - Porque estoy enfermo.
Por que
Sequence composed of the preposition by and the relative pronoun that, is equivalent to using "which", "which", "which" or "which". Which means that there is a reference to an antecedent. (This form is currently used less).
-"Es el parque por que (por el cual) pasábamos de niños".
-"Muchas fueron las infracciones por que lo acusaron."
Porqué
It is a noun and is always preceded by an article or a possessive adjective. Why it can be replaced by "reason", "cause" or "reason".
-"Ellos explicaron el porqué de su conducta"
-"Él tiene un porqué para actuar así"
Because it is used as a noun, it can be used in the plural.
-"Ella comentó los porqués de su comportamiento"
You have to take into account and pay close attention in the tildes, with time you will understand it and it will be easier for you.
