NCERT Solution for Class 9 Science Chapter 1
Matter in Our Surroundings
NCERT Books for Session 2022-2023
CBSE Board and UP Board
Intext Questions
Page No-6
Questions No- 2 Part- B
Comment upon the following: rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density.
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1. Rigidity can be expressed as the tendency of matter to resist a change in shape.
2. Compressibility is the ability to be reduced to a lower volume when force is applied.
3. Fluidity is the ability to flow.
4. By filling a gas container we mean the attainment of shape of the container by gas.
5.Shape defines a definite boundary.
6. Kinetic energy is the energy possessed by a particle due to its motion.
7. Density is mass per unit volume.
(i) Rigidity: The tendency of a substance to retain/maintain their shape when subjected to outside force.
(ii) Compressibility: The matter has intermolecular space. The external force applied on the matter can bring these particles closer. This property is called compressibility. Gases and liquids are compressible.
(iii) Fluidity: The tendency of particles to flow is called fluidity. Liquids and gases flow.
(iv) Filling of a gas container: Gases have particles which vibrate randomly in all the directions. The gas can fill the container.
(v) Shape: Solids have maximum intermolecular force and definite shape.
Whereas liquids and gases takes the shape of container.
(vi) Kinetic energy: The energy possessed by particles due to their motion is called kinetic energy. Molecules of gases vibrate randomly as they have maximum kinetic energy.
(vii) Density: It is defined as mass per unit volume, the solids have highest density.
Rigidity can be expressed as the tendency of matter to resist a change in shape.
Compressibility is the ability to be reduced to a lower volume when force is applied.
Fluidity is the ability to flow.
By filling a gas container we mean the attainment of shape of the container by gas.
Shape defines a definite boundary.
Kinetic energy is the energy possessed by a particle due to its motion.
Density is mass per unit volume.
1. Rigidity: Particles of a solid substance pack very close together leading to more rigidity and fixed shape. The liquid has the least stiffness due to the movement of particles past one another, making it possible for the liquid to assume the shape of the container. Gases are very flexible since their particles keep on moving freely throughout the available spaces.
2. Compressibility: Due to tightly packed solid particles, solids are usually incompressible. Secondly, liquids are not well compressible. Despite that, gases can be considered compressible since their particles are relatively distant, which readily allows their compaction within smaller volumes.
3. Fluidity: Solid has very little fluidity because of movement in its particles is limited. Liquids have a great degree of fluidity because particles can move about in them and assume the shape of the container. The particle movements in gases are fast and random, making gases extremely fluid.
4. Filling a gas container: The solids are in rigid shapes and volume thus occupy little space in the container. They keep a fixed volume, however they adopt the shape of the container. The gases have no definite shapes or volumes, hence, filling up the space of the container they occupy until all space is filled.
5. Shape: Solids have a shape which is not determined by a container; therefore, it has its own form and does not change despite the container. However, liquids conform to the shapes which their containers possess, but exhibit certain volumes. In this case gases have a shape and volume determined by the container in which they are present.
6. Kinetic Energy: The particles are only mobile and therefore have less kinetic energies in solids than liquids. The particles of liquids move more freely than a solid and therefore exhibit moderate kinetic energy. This is because gases have the highest kinetic energy, whose particles move fast and arbitrarily.
7. Density: The solids has a relatively large density because of the close packing of its particles. Liquids have moderate density. Because of wide separation of their particles, gases have a low density.