Topic: Kinetic Energy
Introduction
Matter contains very tiny particles such as atoms, molecules or ions. These particles are always in continuous random motion. The energy which these particles possess that enable them move about is called kinetic energy. The word kinetic is derived from the Greek word “kineo” which means, “I move”. Therefore, kinetic energy is the energy possessed by any body or object as it moves from one place to another.
Statement of the Kinetic Theory
The kinetic theory of gases describes the physical behaviour of a gas in “ideal” or perfect conditions. The statements used to describe the behaviour are called “assumptions” or “postulates”.
They are as follows:
- All gases are made up very tiny particles, which are in constant motion and possess kinetic energy.
- These particles (atoms, molecules or ions) move in a straight line and in every direction
- The molecules collide with each other and with the walls of the vessels in which they are contained
- The collisions made by the gas molecules are said to be perfectly elastic. This means that the collisions do not result in any change in the kinetic energy of the gas.
- A distance that is large compared with their sizes separates the gas molecules from each other. This means that actual volume occupied by the gas molecules themselves is negligible when compared with the volume of the vessel containing the gas.
- An increase in temperature tends to increase the motion of the gas molecules. This implies that the average kinetic energy of the gas molecules is directly proportional to the absolute temperature of the gas
- The increase in temperature leads to increase in volume of the gas
Explanation of Some Phenomena Using Kinetic Theory
Matter exists in three states, namely; solid, liquid and gas. These states are made up of atoms, molecules or ions. One clear difference between these states of matter is the extent (degree) of movement of their particles when heat is applied to them.
Solid State
In solids, the particles are very closely or tightly packed and held firmly by attractive forces. These forces are called forces of cohesion. Examples of cohesive forces are electrovalent, covalent, metallic and even weak ones like Vander Waal forces. It is these forces that hold the particles of a solid together in a fixed position and so restrict their movement from one point to another.
The particles however vibrate about their fixed position. The fixed position of particles of a solid is the reason solids have definite shapes and fixed volumes and are difficult to compress.
Liquids State
Ina liquid, the particles are not so closely packed as in a solid, but they are not confined to a fixed position. They have sufficient kinetic energy to move (vibrate, rotate, translate and even slide) about randomly. Hence, the particles have some freedom of movement although they are still held together by cohesive forces (covalent, Vander Waals Forces) into a fixed volume. So, when a liquid is poured into a vessel, it immediately takes the shape of the container.
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