How is it possible to lose on a video poker machine that has a 100% payout? How does that work?

For example, the game tonight,
Money Line Total
Bucs +145 3.0(even) o38.5(-110)
Carolina -165 -3.0(-120) u38.5(-110)

I am going to have a presentation about texas hold em or poker and I need to teach the class the basic rules. Anyone got any ideas or suggestion on what to teach the class? My presentation has to be 10 mins long. Also I want the class to participate in a 5 min activity that has to do with poker like playing a game or something.