What is the difference between the interaction with a close guy friend and the interaction if a guy likes you(how he acts)? had to do this for health class told us to right about two different social, physical, ect. interactions with opposite sex.

You should really research this instead of asking on , where it's likely that you won't get a descriptive answer for this question. 

I'm a guy, and when I'm just friends with a girl, I try really hard for her not to get feelings for me. I try to keep my distance. I avoid flirting completely, try not to be alone with her, and maybe even try to set her up with other guys.

I'm a fairly shy guy, so when I like a girl, I run out of things to say, flirt pretty badly, and when ''something'' happens I usually tell my close guy friends.

To sum this up,
Close guy friend
Said what I do above, again, I can't speak for all guys when I say this.

If a guy likes you
Social - He could ask a lot of questions in attempt to get to know you better, texts you just to say goodmorning/night, maybe even comments on pictures of your social media page.
Physical - I'd say the guy would attempt to put his arm around you, or just sit really close by. You could also tell if he's nervous whether or not he tries to look relaxed or calm when he's around you. He could also try to act manly (showing off his muscles or body around you, or finding an excuse to lift heavy things).

Lastly, once again I can't speak for all men because one's sign that they like you could be another guy's ''just friends'' sign, but here's my two cents. Good luck.