Class 6 - Science - Chapter 4 - Sorting Of Materials Into Groups

Sorting Of Materials Into Groups

Introduction

We see many objects around us - Paper made from wood, Bulbs made of glass and their filaments made of metal, clothes made of silk and cotton, utensils made of stainless steel and so on. We see that each of these objects are different in appearance, texture, characteristics and features. In this chapter, we will study the features of some of these materials

Objects and Materials

• Objects refers to anything that can be seen or felt. Eg: A water bottle, a mirror, a table, a dress material etc

• Material refers to the matter from which the thing is made. Eg: A water bottle is made of plastic, a mirror is made of glass, a table is made of wood etc

• Understanding of objects and materials helps us to analyze why a certain object is built with a certain material. Eg: Let's say we need to make a pair of spectacles. We could choose from a variety of material available to us - Wood, Glass, Plastic, Gold etc. We cannot obviously use wood because we cannot see through it. We cannot see through gold either and also it is very expensive. We need a material that is light and most importantly transparent. So, we chose either plastic or glass which is transparent and also economical.

Appearance

• Materials look different from each other.
• While some look lustrous and shiny, others look non-lustrous and dull.
• Wood looks non-lustrous.
• Iron, Aluminum, Copper, Gold etc look lustrous, shiny and bright. Generally, such substances which appear bright and shiny are called metals

Hardness or Smoothness

• Materials also feel
• Some of them are soft while the others are hard.
• Materials which can be compressed or scratched easily are referred to as Soft. Eg: Sponge, Cotton
• Materials which are difficult to compress, cut or break are referred to as Hard. Eg: Iron, Copper.

Solubility in water

• Dissolve different solutes like salt, sugar, sand, chalk powder, sawdust in water . Give them a stir and wait for some time.
• While some of them disappear in water others remain as it is in water.
• Soluble substances are those which disappear when mixed with water. Eg: salt, sugar
• Insoluble substances are those which don't disappear or dissolve when mixed with water. Eg: sand, chalk, sawdust

Floatation in water

• Some substances float on water while others sink right to the bottom.
• Objects which are heavier than water sink whereas objects which are lighter than water float on water.
• When leaves from a tree fall on the pond water they float. A paper boat, thin twigs etc are light and they float on water.
• Pieces of stone, heavy bricks etc sink in water

Transparent, Translucent and Opaque

• Materials which allow light to pass through them completely are called transparent objects. Objects on the other side of transparent objects can be seen clearly. Eg: Glass, water and air.
• Materials which don't allow light to pass through them completely are called Opaque objects. Objects on the other side of opaque objects cannot be seen at all. Eg: Wood, metals etc.
• Materials which allow light to pass through them partially are called Translucent objects. Objects on the other side of translucent objects can be seen but not very clearly.Eg: Oily paper, certain types of designed glass, tissue paper etc