Can You Solve this Ice Diamond Riddle? ft. Vsauce’s Michael Stevens

1. Throw it straight down at the ground. It'll bounce straight back up to you, assuming a flat ground (and a reasonably straight throw).

(After watching a bit more... I was close enough.)

2. If it were just an ice cube, the level of the water would stay the same (the buoyant force, i.e. the weight of the water displaced, must be the same as the weight of the ice cube - and water is as heavy as itself, of course). If you were to put a diamond in the ice cube, there is more weight to the ice cube, so the level of the water is higher than the pure ice cube version before it melts. However, once it melts, the diamond takes up less space than the same amount of ice that has been converted into water. Except that we started with water higher than it was before,  so does the diamond make this go down to the same height, more, or less, than pre-melting? ...Uh... I think it should be lower, because if it takes up less volume than the same amount of ice, there should be less volume after melting, too, right? But thinking is hard...

Using the principles from your extremes video where you had a similar challenge, let's consider the case where the diamond is so heavy that the ice just barely has any volume sticking up above it (any heavier, and it violates the setup, since the ice cub does not start out floating). Then, in this case, the diamond is already fully in the water. Thus, the only difference when the ice melts is that the ice becomes water; the diamond doesn't contribute more or less to the water level. So the level of the water decreases! (At least in this limiting case, and I will guess by the wording of the question that this would hold in all similar cases.)