Notes: Materials | Science & Pedagogy Paper 2 for CTET & TET Exams - CTET & State TET PDF Download

Materials 

Different kinds of materials and substances surround human beings. These materials and things can be from the same source or various sources.
For example, a pencil and chair both are made up of the same type of resource, i.e. wood

The properties of the material depend upon the features of the source.

Properties of Material

• Appearance: Their appearance can distinguish different materials. Some are lustrous (shiny) whereas some are dull.
  For example, Silver is shiny, whereas wood is dull.
• Hardness: The property of hardness can also classify materials.
  For example, Iron is hard, whereas cotton is soft.
• Floating property: Materials can also be classified by their tendency to float. Some materials like woodblock can float, whereas others like an iron coin cannot.
• Solubility: Property of a material under which it can be dissolved in water upon stirring is known as solubility.
  Depending on the solubility, materials can be soluble or insoluble.
  Materials which get dissolve in water are known as soluble, and those who do not are known as insoluble.
  For example, salt, sugar, and lemon juice are soluble materials and wood, plastic and oil are insoluble materials.
• Transparency: Those materials which are see-through or which allow light to pass through them without much reflection are said to be transparent materials.
  There can be three types of materials based on transparency:
  (i) Transparent material: Those materials through which the human eye can see easily are said to be transparent materials.
  For example, a glass sheet, clear water, a thin plastic sheet, etc.
  (2) Opaque material: Those substances which reflect light wholly or which are not see-through are said to be opaque materials.
  For example, a wooden table, a Teflon pan, etc.
  (3) Translucent Material: Those materials through which things can be seen but only partially or those objects which reflect a little amount of light are said to be translucent objects.
  For example, Butter paper, a moisture sheet of glass, etc.

Why is the classification of materials necessary?
Classification is a beneficial scientific technique. It helps us study a lot of different subjects with similar properties. For example, a scientist can quickly determine how a small wooden chair and a small wooden stool will behave if he knows about the features of the wood.
So, classification is necessary as it helps us to-

• Group similar objects together and
• Makes their study convenient.

Classification of materials as metals and non-metals

Most of the elements around us can be classified as metals and non-metals based on their chemical and physical properties.

Metals
Materials which are grouped as metals have similar properties, some of those properties are listed below.

Properties of Metals:

• Conductivity: Metals are good conductors of heat and electricity.
• Ductility: They are ductile, i.e. they can be drawn into wires.
• Hardness: All metals are hard. Exceptions are Sodium and potassium are soft and can be cut with a knife.
• Lustre: They are lustrous, which means that they are shiny and have a glowing surface.
• Malleability: They are malleable, i.e. they can be beaten into thin sheets.
• Physical State: Most metals remain solid at room temperature, except for mercury and gallium which are liquid at room temperature.
• Sonorous: Metals are, i.e. they produce ringing sounds when struck. Except for mercury which is found in a liquid state.
  Examples of metal are Copper, Gold, Iron, etc.

Non-Metals
Materials that are grouped as non-metals have properties opposite to that of metals.

Properties of Non-metals:

• Conductivity: Non-Metals are bad conductors of heat and electricity. Except for graphite which is a good conductor of electricity due to the availability of free electrons.
• Ductility: Non-Metals are not ductile, i.e. they brittle (breaks under massive force or pressure).
• Hardness: All non-metals are soft. The exception is diamond.
• Lustre: Non-Metals are not lustrous; they are generally dull.
• Malleability: Non-Metals are non-malleable, i.e. they can’t be beaten into thin sheets.
• Physical State: Non-metals are either stable or gaseous at room temperature.
• Sonorous: Non-Metals are not sonorous, i.e. they do not produce ringing sounds when struck.
  Examples of Non-metal are Carbon, oxygen, etc.

Chemical Properties of Metal and Non-Metals

1. The reaction of metals with oxygen: Metals generally react with oxygen to form metal oxides.
Example,
Copper + Oxygen → Copper Oxide
2Cu + O₂ → 2CuO

2. The reaction of Metals with H₂O: The reaction of metals with H₂O depends on the state of water

• If water is in liquid form, the products of the reaction are Metal Hydroxide + Hydrogen
• If water is in the steam form(Gaseous form), the resultant is Metal oxide + Hydrogen

Example,
Magnesium + Water → Magnesium Hydroxide + Hydrogen
Mg + 2H₂O → Mg(OH)₂ + H₂
Aluminium + steam → Aluminium Oxide + Hydrogen
2Al + 3H₂O → Al₂O₃ + 3H₂

Reactions of metals with solutions of other metals:
In such cases, displacement reactions take place in which more reactive metals displace a less reactive metal.

Example,
Iron + Copper Sulphate → Iron Sulphate + Copper
Fe + CuSO₄ → FeSO₄ + Cu
In this case, as Iron is more reactive than copper, it is displaced.

Uses of metal and non-metal:

Metals and Non-Metals have a wide range of application in our day to day life. It is not possible to list all the methods here. But some of the important ones are as follow:

Uses of Metals

• They are instrumental in making machinery.
• They are used to make utensils.
• They are used to make electrical appliances.
• They are used to keep food and beverages warm.
• They are used in making modern gadgets and science equipment.

Uses of Non-Metals

• Non-metals like oxygen and carbon dioxide are essential for life to survive.
• Compounds of nitrogen and phosphorous are used to make fertilisers.
• These are used in medicines.