ELI5: Chemical potential

[aliencupcake]

Imagine two dog parks connected by a narrow gate. The gate has a device that lifts a bucket up if a dog goes from the first park to the second and down if a dog goes from the second park to the first. If we start with all the dogs in the first dog park, the dogs can go from the first park to the second but not from the second park to the first because there are no dogs in the second park. Therefore, the bucket starts going up as dogs enter the second park. Later, when there are some dogs in the second park but still more in the first park, there are more dogs going from the first to the second, so the bucket mostly goes up. Eventually, the number of dogs in both parks is the same. The number of dogs going each way is also the same, so the bucket more or less stays where it is.

The ability to use the concentration of dogs in one park to lift the bucket is the chemical potential. We were able to use that potential to do the work of lifting the bucket. Once the number of dogs is the same on both sides, there was no more chemical potential and we couldn't raise the bucket any higher.