Question

A burning candle is covered by a jar as shown in the picture. The whole arrangement has a mass of 500 g. What will be the approximate mass of the arrangement when the candle is completely burnt, after four minutes?
A)
0 g



B)
50 g



C)
250 g



D)
500 g

Answer 1

Technically, I can't answer the question, because you won't
let me see the picture that goes along with it and is a part of it. 
But I'm familiar with the set-up, have dealt with the question before,
and I can answer it from my previous experience and general knowledge.

If there is 500g of mass inside the jar when you lower it over
the candle, then there will be 500g of mass at any time after that,
forever, or until you pick up the jar and take some mass out or put
some more in.  It doesn't matter how long you wait.  It also doesn't
matter whether or not the candle is burning, whether or not the sun
is shining on the jar, or whether somebody comes along and spray-paints
the outside of the jar with black paint.  Matter is not created or destroyed. 
Whatever mass was inside when the jar got closed stays in there.
 

Answer 2

The answer is D)500 g  it will not change