How do I know he feels chemistry too?

I recently met a guy and when I see him, talk to him or look into his eyes I feel intense chemistry that I have rarely felt. If it wasn't for this feeling, I probably wouldn't have given him a second look, but now because of this chemistry I feel so physically attracted to him. He seems to make a lot of eye contact when we talk, and I respond (giving him my best seductive eyes hah) and we can be talking about something complete mundane but there's this sizzling chemistry. So, my question is how do I know if he feels it too?

Does strong chemistry, not just a physical attraction, have to be mutual to exist? Or can it be one-sided?

Obviously, physical attraction can be one-sided but what about intense chemistry/sparks/whatever you want to call it?

And how can you tell if it's a mutual attraction and that he isn't just flirty and like this with every girl?