Todavia and aun are more or less the same, for example 

Aún no he hecho los deberes >  I haven´t done my homework yet

No he hecho los deberes todavía> I haven´t done my homework yet

I think that is an other way to say yet

If you want to know the difference between "aun" and "todavia", visit this web: 

http://www.differencebetween.net/language/words-language/differences-between-aun-and-todavia/

If you want to know the difference between "Por" and "para", visit this web:

http://www.studyspanish.com/lessons/porpara.htm

All these webs are in english

The world "escalofriante" depend of the context, 

escalofriante

but if you want to know the meaning, visit this web:

http://www.wordreference.com/es/en/translation.asp?spen=escalofriante#

Hola! Pues mira:

1) the differences between those two are very similar in English

Aún: (yet) I havent't finished my homework yet

Todavia: (still) I still have to finish my homework

2) escalofriante:

creepy or spooky

3) Para y por: It is more difficult and complex 

http://www.lingolex.com/swom/wom-porpara.htm

I recommend you this web page

Good luck! :D