Give reasons for the following observations:-
i) The smell of lighted incense stick spread several meters away.
ii) A liquid has a fixed volume but not a fixed shape.
iii) Ice floats over water.
iv) A wooden table is called a solid at room temperature.
Answers
i)Particles of matter are continuously moving. Rate of movement of particles increases with temperature; therefore the smell of lighted incense stick reaches us several metres away due to diffusion.
ii)In a liquid, the particles are still in close contact, so liquids have a definite volume. However, because the particles can move about each other rather freely, a liquid has no definite shape and takes a shape dictated by its container.
iii)Ice is solid so it floats on water because water molecules expand on freezing and form an open cage-like structure. This leads to a decrease in the density of ice. This means for a given mass ice will have more volume as compared to liquid water. Thus, being lighter ice floats on water.
iv)A wooden table is called a solid because it has a definite shape and volume. It is very rigid and cannot be compressed i.e. it has all the characteristics of solids. Therefore wooden table should be called a solid.