Heat rises, but what does that actually look like? The video shows many examples of air currents, such as a burning match and squeezing helium out of a balloon. It highlights common observations that are rarely seen such as gas vapors...

This video covers refraction and the refractive index, which is based on density. It also explains why the angle of refraction is different than the angle of incidence and how this knowledge is helpful when it comes to lenses.