CHAPTER 1: MATTER IN OUR
SURROUNDINGS
IN-TEXT / PAGE 3
1. Which of the following are matter?
Chair, air, love, smell, hate, almonds, thought, cold,
cold drink, smell of perfume.
Answer: Chair, air, almonds and cold drink
2. Give reasons for the following observation:
The smell of hot sizzling food reaches you several metres away, but to get the smell from cold food you have to go close.
Answer: Solids diffuse at a very slow rate. But, if the temperature of the solid is increased, then the rate of diffusion of the solid particles into air increases. This is
due to an increase in the kinetic energy of solid
particles. Hence, the smell of hot sizzling food reaches
us even at a distance, but to get the smell from cold
food we have to go close.
3. A diver is able to cut through water in a swimming
pool. Which property of matter does this observation
show?
Answer: This observation shows that the particles of
matter have intermolecular spaces. The intermolecular
spaces in liquids is fair enough to let the diver pass
through it.
4. What are the characteristics of particles of matter?
Answer: The characteristics of particles of matter are:
1. Particles of matter have spaces between them.
2. Particles of matter are continuously moving.
3. Particles of matter attract each other.
IN-TEXT / PAGE 6
1. The mass per unit volume of a substance is called density (density = mass/volume).
Arrange the following in order of increasing density -air, exhaust from a chimney, honey, water, chalk,cotton, and iron.
Answer: Air, Exhaust from chimneys, cotton, water,
honey, chalk, and iron.
2. (a) Tabulate the differences in the characteristics of States of matter.
(b) Comment upon the following: rigidity,compressibility, fluidity, filling a gas container, shape,kinetic energy, and density.
Answer: Solid
- Definite shape and volume.
- Not compressible
- There is little space between the particles of a solid.
- These particles attract each other very strongly.
- Particles of solid cannot move freely.
Liquid
- No definite shape but has a definite volume.
- Compressible to some extent.
- These particles have a greater space between them.
- The force of attraction between liquid particles is less
than solid particles.
- These particles move freely.
Gaseous
- Gases neither have a definite shape nor a definite volume.
- Highly compressible
- The space between gas particles is the greatest.
- The force of attraction is least between gaseous particles.
- Gaseous particles are in a continuous, random motion.
3. Give reasons:
a) A gas fills completely the vessel in which it is kept.
b) A gas exerts pressure on the walls of the container.
c) A wooden table should be called a solid.
d) We can easily move our hand in air, but to do the same through a solid block of wood, we need a karate expert.
Answer: a) There is little attraction between particles of gas. Thus, gas particles move freely in all directions.
Therefore, gas completely fills the vessel in which it is kept.