My brain says, "What is the negative logarithm of the hydrogen ion concentration known as?"

Wait, wait. Let me guess.

pH? Yeah, that.

But I never trusted teachers. I had 4 used college chemistry books, and 3 physics texts. (We didn't have the web back then.)

As for critical thinking, it's not different from scientific method. Take a hypothesis and its antithesis, take 'em out for a drive.

ALWAYS be trying to prove yourself wrong.

After repeated failures to be wrong, you might find yourself on the right track.

Don't put ego on the line. That's a whole different subject. In hard sciences ego is bad, unless you're a fundraiser.