Question

why do you think the sulfur hexafluoride isnt escaping from the fish tank? there is no lid on the tank.
sulfur hexafluoride is denser than air so it sank to the bottom of the fish tank.
they didnt use very much sulfur hexafluoride.
it takes at least 15 minutes for it to rise high enough to get out of the tank.
rewatch

Explanation:

To determine why sulfur hexafluoride ($\ce{SF6}$) isn't escaping from the fish tank (no lid), we analyze the options:

• The first option: Sulfur hexafluoride has a much higher density than air (about 5 times denser). Gases with higher density than the surrounding air will sink or stay at the bottom rather than rising and escaping. This is a key concept in gas properties (density relative to air).
• The second option: The amount used doesn’t explain why it doesn’t escape (even a small amount of a dense gas would still sink, not necessarily escape).
• The third option: There’s no scientific basis that it takes 15 minutes to rise; density, not time, drives whether a gas rises/escapes (dense gases sink, less dense rise).

Answer:

The correct option is: Sulfur hexafluoride is denser than air so it sank to the bottom of the fish tank.