Rigid and Fluid
Before we give the definitions of solids, liquids and gases, we should know the meaning of two new terms : rigid and fluid. Rigid means 'unbending' or 'inflexible'. A stone is rigid because it is unbending or inflexible. Fluid means a material which can flow easily and requires a vessel (or container) to keep it.Water is a fluid because if we pour water on the top of a table, it flows over the surface of the table.Moreover, water requires a vessel to keep it. Milk is a fluid and chlorine gas is also a fluid. Keeping these points in mind, we will now define solids, liquids and gases.
A solid is a rigid form of matter. Due to their rigidity, solids have a tendency to maintain their shape when subjected to outside force. Thus, the main identifying characteristic of solids is their rigidity. Solids do not require a container to keep them. A brick and a log of wood are two common solids. A liquid is a fluid form of matter which occupies the lower part of the container in which it is kept. A liquid does not fill the whole container. Being fluids, liquids require a container to keep them. A liquid has a well-defined surface, so a liquid can be kept in an open container. The liquid will not escape from the open container by itself. Water and milk are two common liquids around us.
A gas is a fluid form of matter which fills the whole container in which it is kept. Being fluids, gases also require a container to keep them. A gas does not have a free surface, so a gas has to be kept in a closed container. A gas will escape if kept in an open container. This is why gases are usually kept in air-tight gas cylinders. For example, cooking gas (LPG) is kept in air-tight metal cylinders. From this discussion we
conclude that both, liquids and gases are known as fluids. Please note that the characteristic of liquids and gases of 'flowing' easily is called 'fluidity'. Due to fluidity, liquids and gases change their shapes readily when subjected to outside force. We will now discuss the classification of matter as solids, liquids and gases in detail.
Notes
Sound - Notes
3. 2. Liquid to Gas Change : Boiling (or Vaporisation)
Show Notes
4. 2. Latent Heat of Vaporisation (Liquid to Gas Change)
Show Notes
5. Effect of 'Heating' and 'Cooling' on a Saturated Solution
Show Notes
6. Classification Of Matter As Solids, Liquids And Gases
Show Notes
9. Why Solids, Liquids and Gases Have Different Properties
Show Notes
14. 2. The Particles of Matter have Spaces Between Them
Show Notes
15. 1. Solid to Liquid Change : Melting
Show Notes
16. 3. Gas to Liquid Change : Condensation
Show Notes
20. 1. Latent Heat of Fusion (Solid to Liquid Change)
Show Notes
24. 1. The Particles of Matter are Very, Very Small
Show Notes
26. 4. The Particles of Matter Attract Each Other
Show Notes
28. 3. The Particles of Matter are Constantly Moving
Show Notes
29. Characteristics of Particles of Matter
Show Notes
30. 4. Liquid to Solid Change : Freezing
Show Notes
31. Two More States of Matter : Plasma and Bose-Einstein Condensate
Show Notes
38. The Common Unit Of Temperature and Si Unit Of Temperatre
Show Notes
39. To Show That Solids and Liquids Cannot be Compressed but Gases Can be Compressed Easily
Show Notes
44. To Show that Liquids do not have a Fixed Shape but they have a Fixed Volume
Show Notes
45. To Show the Presence of Water Vapour in Air
Show Notes
49. Gases Can be Liquefied by Applying Pressure and Lowering Temperature
Show Notes
50. To Show that Gases do not have a Fixed Shape or a Fixed Volume
Show Notes
