What does it mean to be alive? And how do you know that something is or isn't?

at what point do you distinguish a thing from the components it's made of?

You say neurons have qualia, but its parts certainly don't. Proteins don't. Lipids don't. Molecules don't. But when you put them together in a specific configuration you say they do?

How is this different from silica? Why can't a thing composed of silica have qualia even if the parts individually don't?

A component of a component of a living thing is not inherently alive. We know neurons are alive not because they are part of the composition of the brain, but because they exhibit properties of life. Neurons being alive doesn't mean that atoms are alive, for instance. Similarly the brain also contains water and fats which are definitely not alive.

You've touched on a very old question in biology: "what does it mean to be alive?" and the answer to that is going to change somewhat on who you talk to and what your subject is. Cells are alive, but in a completely different way from both "simple" multicellular life and "complex" cellular life, but I'm not really aware of a clear boundary existing.

Like all fields of study, there are orders of magnitude more information available at higher levels of research than what most people are taught in school. Clinging to the simplified views of biology organized for university or lower grades as being the end all be all of the field is a great way to harbor ignorance and bigotry.