Is it inches millimeters meters ?
I believe the answer to your question is none of the above
Closed system. If the system is not closed, matter or energy can escape from the system. an example of this is if you react magnesium and hydrochloric acid in a open system. The H₂ gas is going to escape making it look like some of the mass disappeared . in that same reaction some in an open system will also loose heat to the surrounding which will make it look like less heat was produced.
Objects in the fountain appear to be somewhere but isnt
Carbon is a component of so many elements because <span>It can form stable compounds with other elements
and also bond with them.</span>