I am international student and i had a hard time memorizing the words. I'm in panic now. Is it going to be hard for people who don't know many vocabulary words for social workers?

No. Panic will not solve anything. Just take a deep breath and trust that you are going to do well. Social workers tend to work with people who are poor and uneducated. Therefore, they will not have a large vocabulary. Do the best that you can and trust that things will work out as they should. Find a friend to help you practice your vocabulary.