7. An airtight, sealed jar contains an alka-seltzer tablet that is fizzing. The jar is then placed on an electronic
balance. Will the mass increase, decrease, or stay the
same as the tablet fizzes. For credit also EXPLAIN your
answer.

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.