Take this sentence: (which I hope is gramatically correct!)

Fui al cine la semana pasada porque queria ver una pelicula.

There is a mixing of preterite and imperfect, so why if it's clear that the event happened last week, is 'querer' imperfect?

I'm confused!
Fui al cine la semana pasada porque quería ver una película

Quería---> is preterit imperfect because is not clear that you saw the film.
Quise ---> is preterit perfect because with this word is clear that you saw the film.

In the case of preterit imperfect you have two options.

This is indicative (indicativo)
Preterit imperfect (Pretérito imperfecto o Copretérito)
Yo quería
Tú querías
El/Ella quería
Nosotros queríamos
Ustedes queríais / querían
Ellos/ Ellas querían

This is subjunctive (subjuntivo o subordinación)
Preterit imperfect (Pretérito imperfecto o Pretérito)
Yo quisiera o quisiese
Tú quisieras o quisieses
El/Ella quisiera o quisiese
Nosotros quisiéramos o quisiésemos
Ustedes quisierais o quisieseis / quisieran o quisiesen
Ellos/ Ellas quisieran o quisiesen

In the case of the preterit perfect you have this option

Preterit perfect simple (Pretérito perfecto simple o Pretérito)
Yo quise
Tú quisiste
El/Ella quiso
Nosotros quisimos
Ustedes quisisteis / quisieron
Ellos/Ellas quisieron
Many thanks, nicely explained!

I'm slowly getting to grips with verbs after 2 years work! In English, a few tenses cover almost all scenarios however in Spanish there seems to be a particular tense or mood to cover almost every concievable situation.

I find it extremely difficult to converse quickly when I'm constantly thinking about gender and number agreement, word order, grammatical rules and now the correct tense not just in terms of time but for it's exact situation. Phew!!!
It’s OK, with more practice you will be able to write up well in Spanish, now you try to speak and write although you say incongruous things.
The preterite tells the action of your story; the imperfect tells the state of affairs that existed at the time. What you're saying is sort of like this:

I took the action of going (fui) to the movies because I was then in the state of wanting (quería) to see a film.


As used in your sentence, going is an action; wanting is not.

Whether it was last week or last year makes no difference!

Jim
yeah...querer is imperfect because it is a WANT...all wants and needs are imperfect...and in this case it's imperfect because it's not focusing on the time period, but more on the wanting
Anonymousyeah...querer is imperfect because it is a WANT...all wants and needs are imperfect...and in this case it's imperfect because it's not focusing on the time period, but more on the wanting

Sí y no. Se podría expresar querer algo o necesitar algo sin problema en otro tiempo que no sea el imperfecto. Ejemplo:
-Quise traérmela a casa, pero su madre no me dejó.
"Quise" está, evidentemente, en pretérito perfecto simple, y la oración es correcta porque se refiere a un deseo en un momento puntual.
-Necesité un martillo para clavar un clavo, pero me lo prestó el vecino.
"Necesité" está también en pretérito perfecto simple y la oración es correcta, porque necesita el martillo durante un instante determinado y para una determinada acción.