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Physical Classification of Matter
Based on its physical characteristics, matter is divided into solids, liquids and gases.
Solids
The particles are closely packed and bound by strong inter-particle attraction, which makes solids rigid and geometrical. This gives them definite shape and definite volume, for e.g., rock, wood, steel girders etc.
Liquids
The particles are loosely packed and are bound to each other with forces weaker than those of solids. This gives them definite volume but not definite shape. Thus liquids are mobile and take the shape of the container in which they are placed.
Examples: Water, oil, milk etc.Gases
The particles are separated by much greater distances, almost 10 to 100 times the size of the particles. The operating forces of attraction are virtually non-existent in gases, resulting in loosely packed particles, which are free to move in any direction. Thus gases possess neither definite volume and shape and occupy the whole volume of the vessel in which they are placed e.g., air in balloons, oxygen in cylinders.
The three states of matter are inter-convertible. This is achieved by heating and cooling, which affect the kinetic energy of the particles. Heating increases the kinetic energy of matter: as a result, solids when heated become liquids and liquids become gas, when heated.Comparison of the properties of solids, liquids and gases
| Property | Solid | Liquid | Gas |
|---|---|---|---|
| Shape and volume | Because of strong inter-particle forces, solids have definite shape and volume | Because of slightly weaker inter-particle forces, liquids do not have definite shape but possess definite volume | In the absence of any significant inter- molecular forces, there is neither a definite shapes or volume in gases |
| Compressibility and hardness | Solids are generally hard and incompressible, due to closed- packed structure | Liquids are more compressible than solids, due to more empty space | Gases are the most compressible because of large empty space between inter-particles |
| Arrangement of particles | The atoms or molecules are tightly packed. There exists a long range order in solids | The atoms and molecules are packed slightly loose. Only short range order exists | The particles are free to move in any direction and so there is no order |
| Diffusion | These do not diffuse into one another due to the immobility of the particles | Liquids show slow diffusion | Gases undergo diffusion freely |
Chemical Classification of Matter
Based on its broad chemical composition, matter is classified as elements, compounds and mixtures.
Elements
An element is the simplest form of matter that cannot be split into simpler substances or built from simpler substances by any ordinary chemical or physical method. There are 110 elements known to us, out of which 92 are naturally occurring while the rest have been prepared artificially. Elements are further classified into metals, non-metals and metalloids.
Metals
All elements except hydrogen, which form positive ions by losing electrons during chemical reactions are called metals. Thus metals are electropositive elements. They are characterized by bright lustre, hardness, ability to resonate sound and are excellent conductors of heat and electricity. Metals are solids under normal conditions except for Mercury. They are ductile (can be drawn into wire) and malleable (can be beaten into very thin sheets).
Non-metals
Elements that tend to gain electrons to form anions during chemical reactions are called non-metals. These are electronegative elements. They are non-lustrous, brittle and poor conductors of heat and electricity (except graphite). Non-metals can be gaseous, liquids or solids.
Metalloids
Elements that behave like both metals and non-metals are called metalloids.
Common metal, non-metals and metalloids
| Metals | Non-metals | Metalloids |
|---|---|---|
| Gold | Oxygen | Silicon |
| Silver | Carbon | Boron |
| Copper | Hydrogen | Arsenic |
| Iron | Nitrogen | Antimony |
| Mercury | Sulphur | Germanium |
| Zinc | Phosphorus |
Compounds
A compound is a pure substance made up of two or more elements combined in a definite proportion by mass, which could be split by suitable chemical methods.
Characteristics of compound
- Compounds always contain a definite proportion of the same elements by mass. Water as a compound, always contains hydrogen and oxygen in the ratio 1:8 by mass.
- The properties of compounds are totally different from the elements from which they are formed. For example, while water is normally used for extinguishing fire, its elements are not. Hydrogen is combustible and oxygen is a supporter of combustion.
- Compounds are homogeneous.
- During the formation of a compound, energy in the form of heat, light or electricity is either evolved or absorbed. Coal when burnt, gives heat and light energies.
Compounds are broadly classified into inorganic and organic compounds. Inorganic compounds are those, which are obtained from non-living sources such as minerals. For example, common salt, marble and limestone. Organic compounds are those, which occur in living sources such as plants and animals. They all contain carbon. Common organic compounds are oils, wax, fats etc.
