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NON METALS/Materials: Metals and Non-Metals Chapter- 4 Class 8 - CBSE

Non-metals are elements that do not exhibit the characteristics of metals, being mostly poor conductors of heat and electricity, with some exceptions such as graphite. They can exist in solid, liquid, and gaseous states, tend to be brittle and dull in appearance, and are more reactive than metals. Non-metals play essential roles in various applications such as fertilizers, water purification, and medical antiseptics.

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What are Non-Metals? Non-Metals Elements that lack the attributes of metals are called non-metals. Non- metals are good insulators of heat and electricity. They are mostly gases and liquids. Some non-metals are solid at room temperature. E.g. Carbon, sulphur and phosphorus.
LIST OF COMMON NON-METALS Non-metal State Colour Hydrogen Gas Colourless Nitrogen Gas Colourless Oxygen Gas Colourless Fluorine Gas Colourless Chlorine Gas Greenish yellow Bromine Liquid Reddish brown Iodine Solid Greyish brown Carbon Solid Grey Phosphorus Solid Waxy yellow Sulphur Solid Yellow
The various physical properties of the non-metal are, Non-metals are poor conductors of heat and electricity. A notable exception is “Graphite” which is a good conductor of heat and electricity. Non-metal are not ductile in nature except for the carbon nanotube which is ductile in nature. Non-metal are not malleable and they are brittle i.e. they break when hit by a hammer or when force is applied. Non-metal are not lustrous as they do not have any shiny appearance. Non-metals don’t produce a deep ringing sound when they are hit with another material. Thus, they are not sonorous.
Non-metals are dull in appearance and are present in different colours. For example, sulphur is yellow, phosphorus is white or red, graphite is black, chlorine is yellowish- green, bromine is red- brown whereas hydrogen and oxygen are colourless.
Physical State Non-metals can exist in all the three physical states: solid, liquid and gaseous. For example, carbon, sulphur and phosphorus are solid non- metals; bromine is a liquid non- metal; whereas hydrogen, oxygen, nitrogen and chlorine are gaseous non-metals. Diamond ( a non-metal) is the hardest substance known.
Melting and boiling points Non-metals have comparatively low melting points and boiling points This means that non- metals melt and vapourise at comparatively low temperatures. For example, sulphur is a non-metal having a low melting point of 119°C. The majority of non- metals have very low boiling points due to which they exist as gases at room temperature. Only one non-metal graphite has a very high melting point of 3700°C.
Hardness Non-metals are generally soft . Most of the solid non-metals are quite soft. They can be easily cut with a knife. For example, sulphur and phosphorus are solid non-metals which are quite soft and can be easily cut with a knife. Only one non-metal carbon (in the form of diamond) is very hard. In fact, diamond (which is an allotropic form of carbon) is the hardest natural substance known.
Tensile strength Non-metals are not strong. They have low tensile strength. This means that non-metals cannot hold large weights (without breaking). For example, graphite is a non-metal which is not strong. It has a low tensile strength. When a large weight is placed on a graphite sheet, it breaks.
Densities Densities Non-metals have low densities. This means that non-metals are light substances. For example, sulphur is a solid non-metal having a low density of 2 g/cm3, which is quite low. The density of gaseous non- metals is very low. One non- metal iodine has higher density compared to other non-metals.
. Non-metals are not malleable and are brittle. This means that non- metals cannot be beaten into thin sheets with a hammer. Non-metals break into small pieces when hammered. For example, sulphur and phosphorus are solid non-metals which are not malleable, they cannot be beaten into thin sheets with a hammer. Thus, we cannot get thin sheets from non- metals. Sulphur and phosphorus non- metals are brittle. When beaten with a hammer, they break into small pieces. Brittleness is a characteristic property of solid non-metals. Malleability
Ductility Ductility Non-metals are not ductile. This means that non-metals cannot be drawn into wires. They are easily snapped on stretching. For example, sulphur and phosphorus are non- metals and they are not ductile. When stretched, sulphur and phosphorus break into pieces and do not form wires. Thus, we cannot get wires from non-metals. Non- metals are neither malleable nor ductile. Non- metals are brittle.
Lustrousness Non-metals are not lustrous (not shiny). They are dull in appearance. Non-metals do not have lustre which means that non-metals do not have a shining surface. The solid non-metals have a dull appearance. For example, sulphur and phosphorus are non-metals which have no lustre, that is, they do not have a shining surface. They appear to be dull. Exception: Iodine is a non-metal having lustrous appearance. It has a shining surface (like that of metals).
Heat and electrical conductivity Non-metals are bad conductors of heat and electricity. This means that non- metals do not allow heat and electricity to pass through them. For example, sulphur and phosphorus which do not conduct heat or electricity. Many of the non-metals are, in fact, insulators. Exception: A form of the carbon element, diamond is a non-metal which is a good conductor of heat. And another form of carbon element, graphite is a non-metal which is a good conductor of electricity. Being a good conductor of electricity, graphite is used for making electrodes (as that in dry cells).
Non-metals are not sonorous. This means that solid non-metals do not make a ringing sound when we strike them.
Chemical Properties of Non- metals Non-metals have various chemical properties some of the properties of non-metals are listed below. Non-Metals are more reactive than metals. Non-Metals react with oxygen to form acidic oxide. Non-metals react with other non-metals at high temperatures
You should be able to guess why metals are used in making machinery, automobiles, aeroplanes, trains, satellites, industrial gadgets, cooking utensils, water boilers, etc. You are also familiar with the uses of some nonmetals. Here are some interesting ones. Non- metal is essential for our life which all living beings inhale during breathing.
Non-metals used in fertilisers to enhance the growth of plants, Non- metal used in water purification process, Non- metal used in the purple coloured solution which is applied on wounds as an antiseptic, Non-metals used in crackers. You may add some more uses of metals
Differences Between Metals And Non-Metals Metals Non-metals Metals are solids at room temperature except for mercury which is liquid at room temperature. Non-metal exists in all three states i.e. solid, liquid and gases Metals are generally very hard except for Sodium, Potassium and Mercury. Non-metals are generally soft in nature except for Diamond and Graphite which are solid in nature. Metals are malleable and ductile in nature Non-metals are brittle in nature and can break into pieces if struck by a hammer. Metals are electropositive in nature. Non-metals are electronegative in nature. Metals have high densities. Non-metals have very low densities. Metals are lustrous in nature. Non-metals are non-lustrous in nature
Metals and non-metals can be differentiated easily by knowing their physical properties like boiling point, melting point, ductility, malleability, thermal conductivity and chemical properties like electronegativities. Oxidising and reducing properties, corrosion properties, etc. The distinct feature that helps in differentiating metals and non-metals is metals like aluminium and copper is a high thermal and electrical conductivity, whereas non-metals like sulphur and phosphorus metal are the insulators. Some examples of metals include copper, silver, gold, caesium, platinum, aluminium, iron, nickel etc. Examples of non- metals are oxygen, nitrogen, potassium, sulphur, arsenic, etc.
Thank You Nanditha Akunuri www.sonuacademy.in www.nrkacademy.com www.sonuhindiacademy.com