How do moods and emotions affect group dynamics?
Take the group's pulse by going around the room and having each student state one word that describes how he/she is feeling at that moment. Then divide the class into subgroups so that everyone in each subgroup has a similar mood state (usually, the subgroups fall into somewhat generic categories of "anxious/stressed, relaxed/satisfied, happy/feeling-good, angry/annoyed," etc.)
Have each group discuss their mood state among themselves and then create a role play that illustrates that mood. It can be any scenario of their choice. Each group then takes turns improvising their role play before the class.
After each role play, the entire class can discuss how that particular mood affects group dynamics - for example, how are communication patterns, body language, group cohesion, task performance, self-disclosure, the kinds of topics discussed, etc. affected by the emotion in the group.
After all the role plays are finished, have one person from each of the groups come up for one final role play. Ask the class to decide what people would be the best choices (based on the previous role plays), but make sure the people are willing to volunteer. This last role play can be an improvised scene chosen by the class or by you. I usually suggest that they improvise a scene where they are all sitting at table at a wedding reception. This last role play helps illustrate how people in different mood states may interact with each other, and how each person contributes to the overall group dynamics.