Physics Form 1 Notes : CHAPTER FIVE – PARTICULATE NATURE OF MATTER.

CHAPTER FIVE – PARTICULATE NATURE OF MATTER

States of Matter

Matter is anything that occupies space. Matter exists in three states: solids, liquids, and gases. Matter can be changed in various ways, including physical, chemical, and nuclear changes.

1. Physical changes – these are normally reversible and no new substances are formed. Examples include:
   1. Change of state such as melting and vaporization
   2. Thermal expansion due to heating
   3. Dissolving solids in liquids
   4. Magnetizing
   5. Charging electrically
2. Chemical changes – these are irreversible and new substances are formed. Examples include:
   1. Changes caused by burning
   2. Changes occurring in some chemicals due to heating, e.g., mercuric oxide (III). The reactions resulting from mixing chemicals to form other substances.
3. Nuclear changes – these are changes occurring in nuclear substances which give off some particles, e.g., uranium and radium. As this happens, they change into other substances.

Particulate Nature of Matter

Matter is made up of millions of tiny particles which cannot be seen with the naked eye. These particles are called atoms and are made up of sub-atomic particles called protons, neutrons, and electrons. Atoms join together to form molecules.

Movement of Particles

Particles move from one region to another by the process of diffusion. Diffusion is the movement of molecules from regions of high concentration to regions of low concentration until an equilibrium is reached or achieved. Gases diffuse faster or more readily than liquids. The rate of diffusion depends on the arrangement of individual particles.

Solids

Individual atoms in solids have a small space between them; hence, their forces of attraction are very strong. They vibrate in their fixed positions, which gives solids a fixed shape.

Liquids

Forces of attraction between liquid molecules are not as strong as in solids, allowing motion that is not restricted. They collide with each other as they move about. Liquids take the shape of the container they are put in and therefore have no definite shape.

Gases

Molecules or atoms in the gaseous state are further apart, experiencing very small forces of attraction. This makes them almost completely free from each other. We say they are independent in space. Gases have no definite shape or volume but they take up the space and volume of the container they are put in.