Tension doesn't have to be blatent to be present. Let me give you an example that I worked with someone else on, situation changed to save her idea. This is a scene summary, not a scene in of itself, but I think you'll get the idea.
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A passionate, high profile Washington D.C. politician is courting a newly widowed woman with two kids. She recently lost the love of her life to a bomb in Iraq. They've been having a fling, but he wants more. She's still grieving and is worried about publicity.
Where the scene starts is them going to a private club out in Maryland, an exclusive place where politicians, actors, and other people of public interest go in order to get away from the prying eyes of the media. She's reluctant to go because she doesn't want anyone to know they're seeing each other; all other meetings have been clandestine, and she feels that even going to this club is too public. However, he feels the only way to convince her that he loves her is to show her they can be normal even given his status.
This situation makes the entire meal fraught with tension. He's going to be entirely focused on her, making sure she has everything of highest quality, asking her what she wants, suggesting she go out of her comfort zone and try the venison, and ordering expensive wines to go with the meal. He's trying to be normal, and for his life style, this is.
She's a war widow, used to struggling with food stamps and arguing with the military for benefits, not to mention the truth about how her husband died. The lodge isn't a comfortable place for her. Everything is too rich, the food, the wine, the decorations. The waiter being right there to help with all her needs is definitely nerve wracking. She's used to screaming kids at a pizza and party joint or a fast food joint. This place is quiet. She can hear every clank and every murmur; not even the non-descript classical music being played at low volume can mute those sounds to her overtrained ears.
He's trying very hard to keep things casual, asking about the kids, about her day, mentioning politics occasionally, and then he goes off on his obsession with the topic of the day because it's his passion. He's dropping names, and she's twitching. These are powerful people that she only knows from the media, and they have a lot of political power. His casual name dropping only reinforces the gap between them.
Finally, she reacts by flinching, and he realized what he's done. Flash of insight, and he tosses in the napkin and says "Look, I'm done pretending. I'm not a war veteran or a laborer. I'm a politician. I care about this topic. But I also care about you." Pause as she almost bursts into tears. "And I'm pretty sure I love you, too." Now she does burst into tears.
He grabs her hand, and she tries to keep things as quiet as possible so that no one else in the lodge looks, but some of them do, and that's very uncomfortable for her as she cries. She's just hyper-aware, far more than he is about appearances.
He tells her he's sorry, and she hiccups as she accepts and apologizes for ruining the evening. He tells her it's ok. After the water works shut off, he tells her, "I know you love your husband still. All I'm asking is that you get to know me, the real me, and give this thing between us a chance."
She nods her agreement, a few more sobs, and then they dig into the meal, tension relieved...for now.
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The overall setting and scene really isn't one that people would think of as a place for conflict. It breaks all the rules. Passive talking heads over dinner! EEEKKK! Except it doesn't. The dynamic between the two characters is powerful. The situation is uncomfortable. The characters aren't in agreement. The place is filled with potential conflict. That's what tension is--potential conflict. It's waiting for all hell to break loose, for that character to finally put a foot in a trap, or just to open their mouths at the wrong time. An-tic-a-PA-tion.
Hope this helps.
