Question

a girl is cooking some food in the kitchen. the smell of food being cooked soon reaches her brothers room explain how the Smell could have reached her brothers room

Answer 1

due to diffusion.
hot air diffuses with the cold air and the smell reaches brothers room

hope it helps

Answer 2

A girl is cooking some food in the kitchen. The smell of food being cooked soon reaches her brother's room due to the diffusion process.  

  In diffusion, solid or liquid or gas molecules spread from their "higher concentration" region to their "lower concentration" region. The area which one cooks which is mostly kitchen is higher odour concentration area.

  The smell spreads through diffusion to the entire house and thus to the entire house so that, anyone standing at a distance can smell it.