Answer:
The density of the block is 7.4g/ml.
Explanation:
We can determine the volume of the metal block by taking the difference between the volumes measured in the graduated cylinder:

Now, as we know that the average density of an object is calculated dividing its mass by its volume, we can calculate the density ρ of the metal block using the expression:

Finally, it means that the density of the metal block is 7.4g/ml.
There is no direct connection between the speed of an object and its potential energy.
UNLESS the object is falling, and it's GETTING its speed FROM its potential energy. If that's what's going on, then of course if the speed increases, the object's kinetic energy increases, and that increase has to come from using up some of the potential energy.
Are you asking about independent and dependent variables?
Answer:
The boiling point of liquids always increases when pressure is applied on a liquid. This is because the molecules of a liquid will need more energy to turn into a gaseous state when pressure is applied on that substance.