Key Points

A material is any substance used to create an object, such as paper, wood, glass, or metal.

Classification is the method of arranging objects into groups based on common properties they share, helping to organize and understand them.

Materials can be grouped based on various properties such as appearance (lustre), hardness, softness, colour, texture, and whether they are transparent, translucent, or opaque.

Lustrous materials have shiny surfaces and are typically metals like iron, copper, and gold.

Non-lustrous materials do not have a shiny surface, with examples including paper, wood, rubber, and jute.

Hard materials are difficult to compress or scratch, such as stone and iron.

Soft materials can be easily compressed or scratched; examples include an eraser or sponge.

Transparent materials allow things to be seen clearly through them, such as glass, water, and air.

Opaque materials do not allow any light to pass through, meaning one cannot see through them at all; examples include wood and metal.

Translucent materials allow objects to be seen through them, but not clearly, like frosted glass or butter paper.

Soluble materials completely dissolve and disappear when mixed in a liquid, such as sugar and salt dissolving in water.

Insoluble materials do not dissolve or disappear when mixed in a liquid; examples include sand and sawdust in water.

Mass is a property that quantifies the amount of matter present in an object, measured in units like gram ($\text{g}$) and kilogram ($\text{kg}$).

Volume is the amount of space occupied by matter, measured in units such as litre ($\text{L}$), millilitre ($\text{mL}$), or cubic metre ($\text{m}^3$), where $1 \text{ m}^3 = 1000 \text{ L}$.

Matter is anything that occupies space and has mass, encompassing all materials around us.

In SI units, mass is denoted by kilogram ($\text{kg}$) and volume by litre ($\text{L}$) or cubic metre ($\text{m}^3$); always leave a space between the numerical value and the unit, e.g., $7 \text{ kg}$ or $2 \text{ m}^3$.

Classification is useful because it helps us to study and observe patterns in the properties of different things, making it easier to understand their characteristics and uses.