The mass of the products of burning wood is *slightly less* than the mass of the reactants. This is due to the principle of conservation of mass, which states that mass cannot be created or destroyed in ordinary chemical and physical changes.

Here's why:

* Reactants: Wood (mostly cellulose) and oxygen from the air.

* Products: Carbon dioxide (CO2), water (H2O), ash, and a small amount of other gases.

When wood burns, it reacts with oxygen in a process called combustion. The chemical bonds within the wood molecules break, and new bonds form with oxygen, producing CO2 and H2O. A small amount of the mass is also converted into heat and light energy. This energy release is why wood burns.

The missing mass:

While mass is conserved, a tiny amount of mass is converted into energy during combustion, according to Einstein's famous equation E=mc². This amount of mass is so small that it's practically undetectable.

So, the overall mass of the products is slightly less than the mass of the reactants because a small amount of mass is converted into energy.