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# Calculating Free Energy Change

## Demonstrates equations used to describe free energy changes in chemical reactions.

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Practice Calculating Free Energy Change

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Touchdown!

### Touchdown!

Credit: Dani Jace
Source: http://www.flickr.com/photos/85329395@N04/8398076849

The offensive team lines up to kick a field goal, while the defense sets in place to stop the effort. The cheerleaders exhort the crowd to chant “Block that kick!” The ball is hiked, set into place, the kicker swings his leg. The ball slices through the air, over the goal post – three points!

#### Why It Matters

• There is a rhythm to a sports contest, both on the part of the players and the audience. To a great extent the players try to ignore the crowd (especially the boos and taunts) and do their best to focus on the game. At many points during the game, the spectators are, well, spectating. The game goes on with little interaction between players and watchers.
• Cheerleaders play an important role in crowd dynamics (at least at the high school and college level). They lead the audience in chants to encourage their team and help build a tempo for the game. Cheerleaders put energy into the system to develop an organized (less entropy) message to the team. In return, the team feeds off of this energy to be challenged to excel.
• As the game heats up (sometimes literally), the tenor of the spectators changes. The defensive back intercepts a pass intended for the wide receiver and begins his runback. The crowd does not need the structured leading from the cheerleaders. In fact, they are now watching the field with everyone else. Spontaneous shouts break out from the sidelines as the player eludes opposing tacklers. When he crosses the goal line with the winning touchdown, everyone yells and hollers (high entropy, no organized cheer). A spontaneous demonstration!
• Credit: Steven Depolo
Source: http://www.flickr.com/photos/stevendepolo/6224563889/

Cheering from this crowd can get quite loud [Figure2]

#### Show What You Know

1. How old was Gibbs when he graduated from Yale?
2. If the Gibbs free energy for a reaction is negative, is the reaction spontaneous or non-spontaneous?
3. Name an endothermic process that can occur spontaneously.
4. Why is the reaction leading to the formation of ammonia spontaneous at room temperature but not at high temperatures?

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