CLASS 9 What is the state of inter particle distance in a solid, liquid and gas?              In solids, the particles are very close to each other and are bonded by strong forces of attraction so inter particle distance is least. In liquid, the particles are far away from each other and are bonded by weak forces of attraction, so inter particle distance is large.  In gases, particles are very far apart from each other and are bonded by very weak forces of attraction so, inter particle distance is a largest.

Why it is that to smell cold food, we have to go close but smell of hot food reaches us several meters away?     In hot food, the particles are at high temperature so quickly changes to vapour and hence the vapours have greater kinetic energy so travel faster and travel to far off distances. Whereas in cold food, because of temperature being low, particles do not change to vapour state and hence cannot travel faster so the smell does not reaches to a Person sitting far away.

Why is it that a wooden chair should be called a solid and not a liquid?        A wooden chair should be called a solid not a liquid because the particles of wooden chair are very close to each other, it has negligible compressibility and it maintains its shape when subjective to outside force.

What happens when the temperature of the solids increase ? When temperature of the solid is increased, kinetic energy of the particles increases as results particles vibrates more freely with greater speed. They overcome the force of attraction between the particles and start moving more freely.

When heat is being supplied to a solid, then what does the heat energy do to the particles of solid? The heat supplied to the solid, helps the particles to overcome the forces of attraction between them and increases their kinetic energy, as a result of which particle break free the forces of attraction and changes to liquid state.