CBSE Notes Class 6 Science Chapter 2 Sorting Materials Into Groups

Sorting refers to any method of organising objects in a systematic order. It has two distinct meanings: arranging objects in a logical sequence based on a specific criterion and categorising. Categorising is the process of grouping objects that share similar characteristics.

1.0Introduction   

Class 6 science, the sorting materials into groups chapter, helps students identify patterns and relationships, fostering a more organised and systematic approach to understanding their surroundings.

When we look around, we see a wide range of objects. Some are made from different materials, while others are constructed from the same material. For instance, both desks and chairs are made from wood, while pens and dustbins are made from plastic. The choice of material for an object is based on its properties.

Different materials possess distinct properties, and various objects, even with other purposes, can be made from the same material. There are numerous ways to group such objects.

Grouping refers to placing similar items together. In a supermarket, similar products are placed on the same shelf, making it easier to find what you need.

Classification is the process of sorting and organising objects based on certain criteria. This method makes the study of a large number of different objects easier, more systematic, and convenient.

2.0Properties of Materials

1. Appearance:

Materials can be categorised based on their appearance. Some possess lustre, a gentle sheen or soft glow, while others appear plain and dull. Materials with lustre are typically metals, such as gold, copper, aluminium, and iron. Over time, metals may lose their lustre due to exposure to air and moisture. As a result, only freshly cut metals retain their shiny appearance.      

2. Hardness: Materials can be classified based on their hardness.

• Materials that can be easily scratched or compressed are soft, such as rubber or cotton.
• Materials that resist scratching and are challenging to compress are hard, like wood or steel.

3. Solubility: Materials can also be classified as soluble or insoluble in water.

• Soluble materials like sugar and salt dissolve when stirred in water.
• Insoluble materials, like stones and cloth, do not dissolve in water, no matter how much they are stirred.

Solubility of Liquids in Water: When mixed with water, liquids can either be miscible or immiscible. Miscible liquids, such as vinegar and lemon juice, mix entirely with water. Immiscible liquids, like mustard oil, coconut oil, and kerosene, do not mix with water and instead form separate layers.

Solubility of Gases in Water: Some gases, such as hydrogen chloride, carbon dioxide, and ammonia, are soluble in water. Other gases, like nitrogen and hydrogen, are insoluble in water. Water often contains small amounts of dissolved gases, such as oxygen, which is essential for the survival of aquatic animals and plants.

4. Objects That May Float or Sink in Water

When placed in water, some insoluble materials sink to the bottom or float on the surface. For example, objects like leaves and corks tend to float, while heavier materials like rocks and coins sink to the bottom.

• Archimedes, a Greek physicist from the third century BC, discovered the principle of flotation, known as Archimedes' Principle. 
• The principle states that when an object is wholly or partially submerged in a fluid, it experiences an upward force (upthrust) equal to the weight of the fluid displaced by the object.

5. Transparency

Materials can be classified based on their ability to transmit light:

• Transparent Materials: Objects or materials that allow light to pass through them clearly, making it possible to see through them. Examples include glass, clear water, and some plastics.
• Translucent Materials: These objects allow light to pass through, but not completely, resulting in partial visibility. For instance, butter paper and frosted glass are translucent.
• Opaque Materials: Materials that do not let any light pass through, making it impossible to see through them. Examples include metals, wood, and cardboard.

3.0Why Do We Need to Group Objects?

We group objects for several reasons:

• Convenience in storage: Grouping similar objects together makes storing and locating them easier. For example, we keep spices in the kitchen and cleaning products in the bathroom, organising them based on their use.
• Ease of study: Grouping objects helps us study them more effectively, allowing us to observe common features and patterns. This systematic approach simplifies learning and analysis.

This method of categorising items is applied in various fields, from science to everyday life, making tasks more efficient.