They are found in group 3 of the periodic table.
If an object has a higher density than the fluid it is in (fluid can mean liquid or gas), it will sink. If it has a lower density, it will float. Density is determined by an object's mass and volume. If two objects take up the same volume, but have one has more mass, then it also has a higher density.
Using a stove to heat up water.
I believe it is because, Lead has a higher boiling point than zinc. by the time Lead melts and becomes a liquid, the temperature is way higher than the boiling point of Zinc therefore, Zinc becomes a gas.