For the lucky few that are getting on-campus interviews this fall, one of the less-noticeable obstacles to surmount is the lunchtime meal. Usually with more than one person, it's your job (as I see it) as the candidate to help keep the conversation moving. Otherwise, there are
awkward silences -- who wants that? -- and then they'll start whipping out napkins and asking you to explain the 'particle in a box' problem. Helpful topics to consider:
Cute anecdotes: Assuming that you're a good storyteller, there's never any harm in a good story (assuming it's in good taste and non-offensive.) Lab accidents, stories of you falling asleep at 3 a.m. at your columns, stories of you solving your colleagues problems are all fair game.
Asking questions: Many (most?) chemists are introverts; nevertheless, people like attention. If they're game to talk, ask them about their backgrounds, what they like about the company and their current lifestyles. Questions about the area are always helpful and conversation-producing. Treat them like the experts on their organization that they are.
A little bit of dish?: [This one may not be good advice.]
If you can feel the conversation being willing to move in that direction, it's fun to ask people what they think of the management. If you get the typical enthusiasm-less enthusiasm ('oh, they're fine'), they probably don't want to talk about it. But sometimes, you get someone who's willing to tell you the truth; sometimes, even, it's a happy answer.
Good luck out there, folks!