Chapter 4: Sorting of materials into groups (Notes)
Posted on : 15-02-2019 Posted by : Admin

Sorting of materials into groups, properties of material, magnetic materials, conductors, insulators, solid, glass, metallic substances,

Introduction

  • We use a variety of things in our day to day lives for various purposes. All these things are made up of one or more materials. They might be simple or very complex in nature.

Example: Toys, books, tables, chairs, doors are made up of wood.

  • Same things can be made up of different types of materials. For instance, a spoon can be made up of either plastic or steel or any other fiber.

In this chapter, we shall be learning about:

* The importance and need for grouping

* The properties based on which the materials are grouped

 

Importance of grouping

  1. Categorizing materials into groups makes it convenient for study. 
  2. Objects are grouped on the basis of their shape, the materials they are made up of and the properties of these materials.
  3. Materials can be classified based on many different criteria of appearance. Materials differ based on the way they look. Appearance basically indicates colour, hardness, texture and luster.

Luster property

Materials can be grouped as lustrous and non-lustrous based on the luster or shine possessed by them.

Lustrous: Lustrous materials are those that have a shine on them. Due to this property, metals are widely used for making jewelry.

Example: gold, silver and most metals are lustrous in nature.

Non-lustrous: Non-lustrous:  Non-lustrous materials are dull in appearance.

Example: Wood, plastic etc.

Hardness (or) Softness property

Hardness: Hardness: Hardness is another property of materials. Materials which are difficult to compress are called hard substances.

Example: Diamond, stone, iron, wood, steel etc.

It is important to note and remember that Diamond is the hardest natural substance.

Softness: Materials which can be compressed easily are called soft substances. 

Example: Chalk, cotton, rubber, sponge etc.

Transparency property

Materials can be classified as transparent, opaque and translucent based on how they transmit light falling on them.

Transparent: The material which allows light to pass through it is called a transparent material.

Example: Acrylic sheet, glass, water, air etc.

Opaque: Opaque: The material which does not allow light to pass through it is said to be opaque in nature.

Example: Wood, iron, asbestos etc.

Translucent: Translucent materials allow light to pass through them only partially. They are partially transparent and partially opaque.

Example: Butter paper, Frosted glass

State of matter property

Everything in this universe is made up of matter. Matter exists in 3 states - Solid, liquid and gaseous states.

Solid:  A solid has a definite shape and volume.

Example: Stones, wood, plastic, steel etc.

Liquid:  A liquid has an indefinite shape, but a definite volume. 

Example: Water, milk, oil etc.,

Gas:  A gas has an indefinite shape and an indefinite volume. 

Example: Oxygen gas, nitrogen gas, carbon dioxide gas etc.

Solubility or Insolubility property

Soluble substance: A material which easily dissolves in water is called a soluble substance.

Example: Salt, sugar, alum etc.

Insoluble substance: A material which does not dissolve in water is called an insoluble substance.

Example: Sand, chalk, iron etc.

Float or Sink property

Materials that are insoluble in water can either float on the surface of water or sink in it. 

Floating materials: Light materials float on water.

Example: Paper, a plastic ball etc.

Sinking materials: Heavy materials sink in water.

Example: Metals, stones etc.

Metallic or non-metallic property

Metallic substances: Materials which are hard, lustrous and are good conductors of heat and electricity are called metals.

Example: Iron, copper, gold etc.

Non-metallic substances: Materials which are brittle, which don’t have luster and are bad conductors of heat and electricity are called non-metals.

Example: Coal, chalk, rubber, soil etc.

Magnetic property

Magnetic substances: Substances that are attracted to a magnet are called magnetic substances.

Example: Iron, nickel

Nonmagnetic substances: Substances that are attracted to a magnet are called magnetic substances.

Example: Gold, Silver

Conduction of electricity

Conductors: Materials that conduct electricity or let electricity pass through them are called conductors.

Example: Generally metals are good conductors of electricity.

Insulators: Materials that do not conduct electricity or do not let electricity pass through them are called insulators or bad conductors of electricity.

Example: Plastic, wood, air

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