When a perfume bottle is opened, some liquid changes to gas and the fragrance spreads around the room. which sentence explains this?

The molecules of the perfume diffuse through the room at a certain critical concentration and later are detected by our noses. 

2. they have negligible mass.

Aform of energy that is reflected or emitted from objects in the form of electrical and magnetic waves that can travel through space. there are many forms of  electromagnetic  energy including gamma rays, x rays, ultraviolet radiation, visible light, infrared radiation, microwaves and radio waves.