Water absorbs microwaves

In this demonstration we can see how microwaves in a oven light a bulb. This is because the filament acts as an antenna so the waves are turned into electric current. The current makes the filament glow, this is the Joule effect.

If we put water around, we can see that the light bulb doesnt glow becuase the water absorbs most of the energy of the microwaves. This energy heats the water.

Hydrogen generator

How to generate hydrogen (H2) from aluminum (Al) and hydrochloric acid (HCl). It is safer than doing it from electrolysis, since the last also generates oxygen and in same cases (with NaCl as solute) other gases like chlorine (Cl). If the hydrogen is not sepated from the oxygen in the electrolytic tank there is a risk of explosion.

Spring modification

It is easy to modify the length or shape of a spring with heat.