Candles on ridiculously sensitive scales

[Edi]

If we had the capacity to measure masses this small:
Would a candle in a closed jar be just as heavy as identical candle in a jar, but which is on fire?
(say, some chemical touched and ignited the candle in one jar, but is just sitting next to the candle in other, so mass is exactly the same)
As I understand, more energy in a system actually makes it heavier as particles move around and become relatively more massive, but that is if energy is put into the system from outside. What happens in this case, where the energy is actually in the system from beginning, but in a form of chemical bounds?

 

[Dale]

If we had the capacity to measure masses this small:
Would a candle in a closed jar be just as heavy as identical candle in a jar, but which is on fire?

Yes, the mass would be the same.

As I understand, more energy in a system actually makes it heavier as particles move around and become relatively more massive, but that is if energy is put into the system from outside. What happens in this case, where the energy is actually in the system from beginning, but in a form of chemical bounds?

since the energy is already there the system is neither gaining nor losing any energy. (assuming no light or heat escapes the burning jar)

 

[A.T.]

There is another explanatory example of this: Does a wind-up-car become heavier during acceleration, if it reaches relativistic velocities?

 

[Edi]

There is another explanatory example of this: Does a wind-up-car become heavier during acceleration, if it reaches relativistic velocities?

Wind up car would receive energy input from a .. giant hand, from outside the system. (?)

 

[Graniar]

What happens in this case, where the energy is actually in the system from beginning, but in a form of chemical bounds?

Mass of molecule is a bit less than of summ of it's unbounded atoms. The same as for nuclear reactions, which is more observable, for example, compare mass of He4 to 4 Hydrogen.

 

[A.T.]

Wind up car would receive energy input from a .. giant hand, from outside the system. (?)

Not during acceleration. It is winded up at rest, then released.