[ncmncm]

> "tell kids in biology classes a more convenient definition"

That is where you get conflict. Too simple? Too inclusive? Too not? But it's the only place where you need one that doesn't mention biologists.

"Life is a process that uses energy obtained from outside a boundary to reduce entropy inside it."

You have define entropy, then, which kids might not like much.

[waserwill]

These are good questions. I care most about these sorts of definitions when teaching, since they can orient students and describe what it is you are talking about. Some criteria I was taught about life:

> 1. Reproduces itself/making things similar to itself (sort of; viruses are on the periphery, prions...).

> 2. Metabolizes chemicals for energy

> 3. to grow, and as a result,

> 4. produces waste.

> 5. Reacts to stimuli in the environment.

> 6. Maintains homeostasis (reacts to stimuli in itself and keeps 1-5 going).

I really like these, because while they are wrong on some level, they are pedagogically useful: they orient students to what life does, what we can learn about it, and what sorts of data we can collect. Plus, it points towards both ecology and evolution.

Your definition is more encompassing in a way, so it better describes any life-form, but so encompassing that it also describes crystalization! (The parallels between life and crystals are admittedly interesting, especially when thinking about abiogenesis.)

Just from a practical perspective, I would rather start from those criteria than from physical chemistry and physics. Then, come exceptions and complications, which are great! Even when learning physics, I recall every other lecture beginning with, "Those assumptions we made were wrong. Instead, ..."