The liter is a volume unit. The number 54.07 grams has two significant figures. 0.0001 has five significant figures. Exact numbers have an infinite number of significant figures. There are 60 seconds in a minute, so in 4 minutes there are 2400 seconds.
Metals have large specific heats, that is why they conduct heat well.
19.Density is a property that depends on the size of an object. It is independent of amount. Specific gravity has no units. The units all cancel.