1. Which of the following are matter?
Chair, air, love, smell, hate, almonds, thought, cold, lemon water, the smell of perfume.
Ans: The following are matter:
Chair
Air
Almonds
Lemon water
The smell of perfume (Smell is considered matter due to the presence of volatile substances in the air, which occupy space and have mass.)
Question 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.
Ans: Particles in the air gain high kinetic energy when exposed to higher temperatures. This allows them to move faster and travel farther, enabling the smell of hot sizzling food to reach a person even from several meters away.
3. A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?
Ans: This observation shows that water molecules have weak forces of attraction. This property allows the diver to move through water easily.
4. What are the characteristics of the particles of matter?
Ans: The characteristics of particles of matter are:
Particles have intermolecular spaces.
Particles are in constant motion.
Particles attract each other.
All matter is made up of extremely small particles that can exist independently.
5. 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 chimneys, honey, water, chalk, cotton and iron.
Ans: The substances arranged in the order of increasing density are:
Air < Exhaust from chimneys < Cotton < Water < Honey < Chalk < Iron
6.(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.
(a) Differences in the characteristics of the three states of matter
(b) Definitions of key properties
Rigidity: The ability of a substance to maintain its shape when subjected to external force.
Compressibility: The ability of particles to reduce intermolecular space under external force, increasing density.
Fluidity: The ability of a substance to flow or move freely.
Filling a gas container: Gas particles move randomly, filling the entire space of the container.
Shape: The definite structure of an object enclosed within a boundary.
Kinetic energy: Energy possessed by particles due to their motion. It increases in the order:
Solids < Liquids < Gases.
Density: Mass per unit volume of a substance/matter is known as its density i.e. density = mass/volume
7.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.
Ans:
(a) A gas fills completely the vessel in which it is kept
Gas particles have a very low force of attraction and are free to move in all directions. This allows them to spread and fill the entire vessel.
(b) A gas exerts pressure on the walls of the container
Gas particles move randomly and collide with the walls of the container. These collisions exert force, leading to pressure on the walls.
(c) A wooden table should be called a solid
A wooden table has a fixed shape and volume. Its particles are tightly packed and do not conform to the shape of a container, fulfilling the characteristics of a solid.
(d) Why can we move our hand through air but not through a solid block of wood?
Air particles are loosely packed with large spaces between them, making it easy to move through. In contrast, particles in a solid block of wood are tightly packed with strong attractive forces, requiring significant effort to move through.