Metaphors, Analogies, and Scaling
Metaphors, Analogies, and Scaling
The following paragraph is about explaining a chemical potential energy surface. It starts by establishing the idea of molecular energy states by using the terms “comfortable” and “uncomfortable” metaphorically. To make the terms “high-energy state” and “low-energy state” more relatable to the audience, I used an analogy relating repelling atoms to repelling magnets. I chose this because people have physically felt the energy it takes to hold repelling magnets together. I considered using the analogy of the state of stretching out one’s body (which takes energy to maintain) versus the state of slouching (which doesn’t), but the analogy based on magnets is closer to what is actually happening on an atomic level: atoms are repelled by electronic forces. With this foundation in hand, I introduced an analogy relating the reaction coordinates of a chemical process to a mountain range. This is an analogy that needs elaboration to be well-understood. I referred to high- and low-energy states as “mountains” and “valleys” to make the ties between a topographic map and the potential energy states of a molecule clear. I finish with another analogy in the final sentence, in which I used this established framework of a mountain range to extend the concept further. In this sentence, I moved beyond what the potential energy surface is to how it is applied to describe reactions.
Molecules are not still, unmoving objects. They vibrate, with the atoms in a molecule moving around in relationship to other atoms in the molecule, as well as atoms in nearby molecules. Uncomfortable positions due to repulsion between atoms are “high-energy” states for molecules to be in; comfortable positions that lessen the amount of repulsion atoms feel are “low-energy” states. You can think of this like pushing two repelling magnets towards each other. You have to use energy to hold the magnets together with your hands when they are in an uncomfortable position close together (a high-energy state), and don’t need to use so much energy when they are comfortably far apart (a low-energy state). As molecules vibrate and move in relationship to each other, you can map the positions they might be in like a mountain range: valleys are positions in which molecules are in comfortable (low-energy) states and mountain peaks are positions in which molecules are in uncomfortable (high-energy) states. When we say that the way molecules get from one state to another in a reaction is the “lowest energy pathway,” we mean that they move through a series of positions that are relatively easy for them to take, like walking the easiest route through the valleys between mountains instead of using a lot of energy to hike all the way to the top of a mountain and back down the other side.
The following is an analogy one could use to explain the poor solubility of nonpolar molecules in polar solvents.
Trying to mix nonpolar molecules (which are not very attracted to anything) into a large group of polar molecules (which are very attracted to each other) is like trying to shove a few ping-pong balls into a bucket of magnets.
This is a metaphor for ring strain in organic molecules. It does have a limitation in that the forces causing ring strain would come from the arms of the coat hanger repelling each other, rather than from the bonds trying to keep a rigid form.
Chemical bonds tend to form specific angles due to repulsion between the electrons that form those bonds. A molecule in a small ring is a squeezed coat hanger that doesn’t like being bent.
This metaphor relates the inside of a micelle (which is nonpolar) to an island. I assumed the audience is familiar with the word “micelle” for this example.
Inside the body, a micelle is an island in an ocean of water on which organic molecules can gather.
When it hit the Martian atmosphere, the Mars Pathfinder rover decelerated from 16330 mph to 900 mph in 2.7 minutes. This is like going from 80 mph on the freeway in your car to a complete stop in 0.85 seconds.
The ice that melted from Greenland between 2002 and 2017 produced 75.6 trillion gallons of water that went into the ocean. This is enough water to fill Lake Tahoe almost twice. Or, if all 56,400 people in Greenland drank a gallon of that water every day, it would take them 3.7 million years to finish drinking it.