Setting the Scene: The teacher has described the use of the molecular model kits to the class. The colours were explained (black = carbon, red = oxygen, blue = nitrogen, etc) and the use of sticks (single bonds) and springs (multiple bonds) are described. She has now asked that the students, in groups of three, build several different molecules, like H2O, CCl4 and NH3.
The activity is going along well, until one group notices that their kit is missing nitrogen. A girl (let's call her Susie) in the group raises her hand to get the teacher's attention.
Susie (waving hand): "Miss, we don't have any nitrogen."
Teacher (voice raised to address the class): "Do any of the groups have an extra nitrogen to lend to Susie's group?"
All the groups, engaged in their work, ignore this request.
Teacher (slightly exasperated): "Okay folks, listen up! I need to know. Who's got blue balls?"
Several boys raise their hands, while stifling laughter. All the girls look bewildered.
Teacher: "What I mean is...well......c'mon you guys......hey, stop laughing......oh, nevermind."