Can heat be transformed into matter? Heat is a form of energy.
Heat gets created by mechanical or chemical processes that act, most of them, on matter.
Considering those processes that act on matter and create energy, can heat be transformed back into substance again? Or does it simply, part of it, gets wasted into nothingness?
Or energy (heat) is one result of matter getting transformed, that cannot be captured.
 A: And endothermic reaction is one that absorbs heat, and that means the total mass of the products will be slightly greater than the total mass of the reagents. The increase in mass will be equal to the heat absorbed divided by $c^2$ i.e. the mass change will be given by Einstein's famous equation $E = mc^2$. This is an example of heat being converted to mass.
Note however that endothermic reactions are generally only possible when there is a large and positive entropy change. Though they offer a way for mass to be converted to heat and then back to mass again, this can only occur when an entropy gradient permits so it can't occur indefinitely.
An example of an endothermic process is dissolving most ionic solids in water. The heat of solution is negative for most ionic solids i.e. when you dissolve them in water the solution decreases in temperature. The ionic solid only dissolves because the entropy of solution is large and positive.
A: Matter is atoms and molecules, whereas heat is a change in energy (not even the energy itself) of these atoms and molecules. So they are not really the same thing.
The Einstein's equation, $E=mc^2$, does allow for transformation of energy into matter and vice versa, which is what happens in nuclear reactions. However this is not the heat transfer, which is a purely thermodynamic concept.
