Class 6 — Chapter 6: Materials Around Us

6.1 Observing Objects Around Us

Material: Any substance that is used to create an object is referred to as a material. All things around us are made up of one or more materials like paper, wood, cloth, glass, metal, plastic, clay, etc.
Ancient Pottery: Earliest pottery in the Indian subcontinent dates back 7,000 to 8,000 years (Ganga plains and Baluchistan). The Sindhu-Sarasvatī (Harappan) Civilisation developed advanced wheel-turned pottery, painted with designs and baked in kilns (terracotta).

6.2 How to Group Materials?

Classification: The method of arranging objects into groups based on common properties.
An object can be made from different materials (e.g., a tumbler made of glass, plastic, or metal), and a single material can be used to make many different objects.

6.3 Properties of Materials

Lustrous: Materials that have shiny surfaces (typically metals like iron, copper, aluminium, and gold). Some metals may lose their shine and look dull due to exposure to air and moisture.
Non-lustrous: Materials that do not have a shiny surface (e.g., paper, wood, rubber, jute).

Soft: Materials that can be easily compressed or scratched (e.g., sponge, eraser, candle).
Hard: Materials that are difficult to compress or scratch (e.g., stone, iron, wood). Hardness is a relative property.

Transparent: Materials through which things can be seen clearly (e.g., glass, water, air, cellophane paper).
Opaque: Materials through which you cannot see at all (e.g., wood, cardboard, metals).
Translucent: Materials through which objects can be seen, but not clearly (e.g., butter paper, frosted glass).

Soluble: Materials that completely dissolve/disappear when mixed in water (e.g., sugar, salt, oxygen gas).
Insoluble: Materials that do not mix with water and do not disappear even after stirring for a long time (e.g., sand, sawdust, chalk powder).
ORS (Oral Rehydration Solution): Prepared by mixing six teaspoons of sugar and half a teaspoon of salt in one litre of boiled and cooled water.

Mass: A property that measures how heavy or light an object is. Heavier objects have more mass.
Volume: The space occupied by matter represents its volume.

6.4 What is Matter?

Matter: Anything that occupies space and has mass is called matter. Mass and volume are properties possessed by all materials.
Units of Mass: Gram (g) and Kilogram (kg). SI unit is kilogram (kg).
Units of Volume: Litre (L) and Millilitre (mL). SI unit is cubic metre (m³). Note: 1 m³ = 1000 L.

Ayurveda describes physical matter using 20 properties (guṇa), arranged in 10 pairs of opposites:

Science: Class 6 — Chapter 6: Materials Around Us