Illustrations
Question 1: Kitchen salt (NaCl) when added to water, gets evenly distributed in it. Which characteristic of particles of matter is exhibited by this ?
Solution: It shows that there is enough space between the particles of matter.
Question 2: Define diffusion, is it faster in winter or summer season ?
Solution: The phenomenon of intermixing of particles of different types of matter, on their own, is called, diffusion. The rate of diffusion becomes faster with an increase in temperature due to increase in K.E. of moving particles. Hence diffusion is faster in summer than in winter.
Question 3: When we light an incense stick (agarbatti) in a corner of our room, why does its fragrance spread in the whole room very quickly ?
Solution: When we light an incense stick, the temperature rises and hence kinetic energy of the incense particles also increases. As a result, the incense particles move rapidly and thus the rate of diffusion of incense particles with air particles becomes faster. That is why, fragrance of agarbatti (when we light it) spreads in the whole room very quickly.
Question 4: Give reasons for the following observations. The smell of hot sizzling food reaches when you are several meters away, but to get smell from the cold food, you have to go close to it ?
Solution: The particles of matter are continuously moving, but their average speed increases with increase in temperature due to increase in K.E. of moving particles.
Now since, the particles of hot vapours coming out of hot sizzling food move faster, therefore, they easily reach you even when you are several metres away. On the other hand, the particles of vapours coming out of cold food travel only slowly and hence do not reach you. Therefore, to get the smell from cold food, you have to go close to the food.
In short, due to diffusion, which becomes faster at higher temperature, vapours from hot sizzling food move faster and reach you several metres away. But you have to go close to get smell from cold food.
The matter around us exists in three physical states on the basis of physical properties.
(a) Water exists as ice (solid state), as liquid (liquid state) and as steam (gaseous state).
(b) Bones and teeth are solids, the blood that flows in our veins is a liquid and the air that we breathe in is a gas.
The three physical states of matter (i.e solid, liquid or gaseous) arise due to variation in the characteristics of the particles of matter