Cap Vs Lid?

New2grammarPot Lid

Lunch Box Lid

Beer Bottle Cap

Coke Can Lid

Heinz Cap

A cookie jar Lid

salt bottle Cap

flask Cap

Now ask me why - - - - A little more difficult
My answer would be that a lid 'sits' on the top on something, as in the case of a pot or pan so it use to cover - not seal

but a cap implies that you can seal something to prevent spillages

There's a mistake. I should be Salt Shaker

Salt shaker - tricky one - - but I think lid, as it allows salt to pass through it when shaken
also known as a salt-cellar

Your definition covers all but one:Lunch Box Lid

My lunch box is airtight

Because a box has a lid NOT a cap
- though I agree it doesn't meet my definition - but as we all know there are always exceptions.
It may be my definition is not 100% right, but it's how I see it

What do you call the piece that covers a cell phone's battery compartment?

cover or phone cover