Question

We can easily move our hand in air to do the same through a solid block of wood we need a karate expert

Answer 1

It is because the atoms in air are freely moving here and there and in solid block the atoms are tightly packed so we need a karate expert

Answer 2

Yes this is true.....
When we are waving our hand hand in air then we can easily do that because the particles of air(gaseous state) are very loosely packed i.e have spaces between them. On the other hand in solids there are no intercellular spaces thus we can not move our hand there....
#Hope it helped !