Both have the same relative masses, hence there is no difference in water legels

For Q5, now the jar of nitrogen dioxide is on top and the jar of regular air is at the bottom.

After a long period of time, the gases will evenly distribute themselves across the entire combined space, and as such, both jars will reach an equilibrium. Both jars will be brown in colour after a very long period of time.

Q1a

This is because particles of a substance move from a region of higher concentration to a region of lower concentration (think of what happens when you add Milo powder into water and stir the resulting mixture) and thus diffuse through the nearby surrounding air to reach the entire room.

Q1b

This is because the particles gain more energy with an increased temperature, allowing particles to collide more effectively and frequently. As such, we can expect a higher frequency of movements and effective collisions amongst particles, allowing the rate of diffusion to increase at a higher temperature.