When either pan is heated, energy is transferred via conduction. Conduction is the process by which heat is transferred through a material, the average position of the particles remaining the same.
When the pans are heated, the particles in each pan vibrate faster and transfer this energy rapidly to neighboring particles.
The pan with a thicker base has more particles in it than the pan with lighter weight base. Note that, The rate of heat transfer is inversely proportional to the thickness of the material in question. Hence, the thicker the base, the more the number of particles present and the longer the time it takes for the food to cook.
In order to get HgO you would need 2Hg+1O2=2HgO. Since oxygen is diatomic you need two when it stands alone causing you to need two mercuries to balance out the reactants and the product I hope this helps