class 9th important notes of
science ch1
Exercise-1.1-1.2 Page: 3
1. Which of the following are matter?
Chair, air, love, smell, hate, almonds, thought, cold, lemon water, the smell of
perfume.
Solution:
The following substances are matter:
Chair
Air
Almonds
Lemon water
The smell of perfume (Smell is considered as a matter due to the presence of some
volatile substances in air that occupy space & have mass.)
2. Give reasons for the following observation:
The smell of hot sizzling food reaches you several meters away, but to get the
smell from cold food, you have to go close.
Solution:
Particles in the air, if fueled with higher temperatures, acquire high kinetic energy, which
aids them to move fast over a stretch. Hence, the smell of hot sizzling food reaches a
person even at a distance of several meters.
3. A diver is able to cut through water in a swimming pool. Which property of
matter does this observation show?
Solution:
The diver is able to easily cut through the water in the swimming pool because of the
weak forces of attraction between water molecules. It is this property of water that
class 9th important notes of science ch1 1
, attributes to easy diving.
4. What are the characteristics of the particles of matter?
Solution:
The characteristics of particles of matter are as follows:
(a) Presence of intermolecular spaces between particles
(b) Particles are in constant motion
(c) They attract each other
(d) All matter is composed of very small particles which can exist independently.
Exercise-1.3 Page: 6
1. The mass per unit volume of a substance is called density.
(density=mass/volume). Arrange the following in the order of increasing density –
air, exhaust from the chimneys, honey, water, chalk, cotton and iron.
Solution:
The following substances are arranged in increasing density:
Air
Exhaust from chimney
Cotton
Water
Honey
Chalk
Iron
2. Answer the following.
a) Tabulate the differences in the characteristics of matter.
b) Comment upon the following: rigidity, compressibility, fluidity, filling a gas
container, shape, kinetic energy and density.
Solution:
class 9th important notes of science ch1 2
science ch1
Exercise-1.1-1.2 Page: 3
1. Which of the following are matter?
Chair, air, love, smell, hate, almonds, thought, cold, lemon water, the smell of
perfume.
Solution:
The following substances are matter:
Chair
Air
Almonds
Lemon water
The smell of perfume (Smell is considered as a matter due to the presence of some
volatile substances in air that occupy space & have mass.)
2. Give reasons for the following observation:
The smell of hot sizzling food reaches you several meters away, but to get the
smell from cold food, you have to go close.
Solution:
Particles in the air, if fueled with higher temperatures, acquire high kinetic energy, which
aids them to move fast over a stretch. Hence, the smell of hot sizzling food reaches a
person even at a distance of several meters.
3. A diver is able to cut through water in a swimming pool. Which property of
matter does this observation show?
Solution:
The diver is able to easily cut through the water in the swimming pool because of the
weak forces of attraction between water molecules. It is this property of water that
class 9th important notes of science ch1 1
, attributes to easy diving.
4. What are the characteristics of the particles of matter?
Solution:
The characteristics of particles of matter are as follows:
(a) Presence of intermolecular spaces between particles
(b) Particles are in constant motion
(c) They attract each other
(d) All matter is composed of very small particles which can exist independently.
Exercise-1.3 Page: 6
1. The mass per unit volume of a substance is called density.
(density=mass/volume). Arrange the following in the order of increasing density –
air, exhaust from the chimneys, honey, water, chalk, cotton and iron.
Solution:
The following substances are arranged in increasing density:
Air
Exhaust from chimney
Cotton
Water
Honey
Chalk
Iron
2. Answer the following.
a) Tabulate the differences in the characteristics of matter.
b) Comment upon the following: rigidity, compressibility, fluidity, filling a gas
container, shape, kinetic energy and density.
Solution:
class 9th important notes of science ch1 2
