Pronunciation question

In lesson 1.3 we learned two verbs: SAPERE and CONOSCERE

I noticed that the accented syllable in sapere is saPEre and in conoscere it is coNOscere.

Is there a rule about which syllable is accented in Italian words?

Thank you!

Indeed, as you noticed, the stress in Italian is variable,  just like in English.
There are no fixed rules but patterns. Most words in Italian are stressed on the penultimate syllable (e.g.  man-gia-re).

Other words are, instead, stressed on the third-to-last syllable. Usually, these are words ending with the following suffixes:

-agine,  -aggine,  -igine,  -iggine,  -edine,  -udine,  -abile,  -evole,  -ibile,  -ico,  -aceo, -ognolo,  -oide,  -cefalo,  -crate,  -dromo,  -fago,  -filo,  -fobo,  -fono,  -gamo,  -geno,  -gono,  -grafo,  -logo,  -mane,  -metro,  -nomo,  -stato,  -tesi,  -ttero,  -fero,  -fugo,  -voro

However, there are exceptions, just like "co-no-sce-re". 
The best thing is to memorize the stress whenever you learn new vocabulary :) 

For additional information, it's great to know that words are classified in "tronche", "piane", "sdrucciole" and "bisdrucciole" according to the stressed syllable:

parole tronche (stress on last syllable): e.g. caffè, città
parole piane (stress on second-last syllable): e.g. libro, cosa
parole sdrucciole (stress on third-last syllable): e.g. tavolo, origine
parole bisdrucciole (stress on fourth-last syllable): e.g. verificano

Hope this helps! :)