The various kinds of substance that make up matter can be divided roughly into three categories, namely, gases, liquids and solids. These are called as three states of matter. These states can be considered to arise as a result of competition between two opposing molecular forces, namely, the force of attraction which tends to hold the molecules together, and the disruptive force due to the thermal energy of the molecules. If the disruptive forces due to thermal energy are much greater than the forces of attraction, then we have matter in its gaseous state. Molecules in the gaseous state move with very large speeds and the forces of attraction amongst them are not sufficient to bind the molecules at one place, with the result that the molecules move practically independent of one another. Because of this feature, gases are characterized by marked sensitivity of volume change with change of temperature and pressure. There exists no boundary surface and, therefore, gases tend to fill completely any available space, i.e. they do not possess a fixed volume.
lf the forces of attraction are greater than the disruptive forces due to thermal energy, we have matter in the liquid state. Molecules in the liquid state too have kinetic energy but they cannot go very far away because of the larger forces of attraction amongst them. Due to this feature, liquids have definite volume, but they do not have definite shape. They take the shape of the vessel in which they are placed.
Gaseous state is the simplest state of matter. Throughout our life we remain immersed in the ocean of air which is a mixture of gases. We spend our life in the lowermost layer of the atmosphere called troposphere, which is held to the surface of the earth by gravitational force. The thin layer of atmosphere is vital to our life. It shields us from harmful radiations and contains substances like dioxygen, dinitrogen, carbon dioxide, water vapour, etc. Let us now focus our attention on the behavior of substances which exist in the gaseous state under normal conditions of temperature and pressure.
The various kinds of substance that make up matter can be divided roughly into three categories, namely, gases, liquids and solids. These are called as three states of matter. These states can be considered to arise as a result of competition between two opposing molecular forces, namely, the force of attraction which tends to hold the molecules together, and the disruptive force due to the thermal energy of the molecules. If the disruptive forces due to thermal energy are much greater than the forces of attraction, then we have matter in its gaseous state. Molecules in the gaseous state move with very large speeds and the forces of attraction amongst them are not sufficient to bind the molecules at one place, with the result that the molecules move practically independent of one another. Because of this feature, gases are characterized by marked sensitivity of volume change with change of temperature and pressure. There exists no boundary surface and, therefore, gases tend to fill completely any available space, i.e. they do not possess a fixed volume.
lf the forces of attraction are greater than the disruptive forces due to thermal energy, we have matter in the liquid state. Molecules in the liquid state too have kinetic energy but they cannot go very far away because of the larger forces of attraction amongst them. Due to this feature, liquids have definite volume, but they do not have definite shape. They take the shape of the vessel in which they are placed.
Gaseous state is the simplest state of matter. Throughout our life we remain immersed in the ocean of air which is a mixture of gases. We spend our life in the lowermost layer of the atmosphere called troposphere, which is held to the surface of the earth by gravitational force. The thin layer of atmosphere is vital to our life. It shields us from harmful radiations and contains substances like dioxygen, dinitrogen, carbon dioxide, water vapour, etc. Let us now focus our attention on the behavior of substances which exist in the gaseous state under normal conditions of temperature and pressure.