Materials Around Us

Observing Objects Around Us

Introduction

• We encounter various objects daily made of different material, each with distinct shapes, colors, and uses. Grouping these objects helps us understand and study their properties more effectively.

What is Material?

• Everything we use is made from some material.
• Materials can be things like paper, wood, cloth, glass, metal, plastic, and clay.

How to Group Materials?

What is Classification?

• Classification means organizing objects into groups based on shared features.

Why Group Objects?

• Grouping objects makes it easier to locate and study them.
• Grouping helps us understand how materials and objects are similar or different.
• Grouping helps in deciding which material suits an object’s purpose.
• Grouped objects reveal patterns and similarities, aiding in better understanding and practical usage.
• Whether it’s at home or in shops, objects are often classified for easier use.
• For example, in the kitchen, utensils are often grouped together.

Ways to Group Objects

• By Shape: Objects can be categorized based on shape (e.g., round objects like balls, apples).
• By Color:
• By Hardness:
• By Material: Objects can also be grouped based on the materials they are made of (e.g., plastic, metal).

Choosing Materials for Objects:

• We select materials based on their properties and the purpose of the object.
• For example, a tumbler needs to hold water, so it should be made of a material( glass or metal, not cloth) that doesn’t leak.

Key Properties of Materials

a. Appearance

• Definition: How a material looks (e.g., shiny, dull).
• Example: Metals like iron, copper, and aluminum often have a shiny surface or lustre.
• 1. Lustrous (Shiny) Materials: Materials with shiny surfaces are called lustrous, metals like iron, copper, aluminium, gold are usually lustrous.
• Some metals lose their shine over time due to air and moisture.
• 2. Non-lustrous (Not Shiny) Materials: Materials without a shiny surface (e.g., paper, wood, rubber).
• Not all shiny materials are metals; sometimes, polishing makes them shiny.

b. Hardness

• Definition: The ability to withstand scratches or compression.
• Example: Iron is hard and difficult to compress, while cotton is soft and compressible.
• Hard Materials: Difficult to scratch or compress (e.g., stone, iron).
• Soft Materials: Easy to scratch or compress (e.g., eraser, chalk).
• Hardness is a relative property
  • Example: Rubber is harder than a sponge but softer than iron.

c. Transparency

• Transparent: You can see clearly through them (e.g., glass, water).
• Opaque: You cannot see through them at all (e.g., wood, metals).
• Translucent: You can see, but not clearly (e.g., butter paper, frosted glass).

d. Solubility

• Definition: Whether a material can dissolve in water or not.
• Examples:
  • Soluble Materials: Sugar and salt dissolve in water (e.g., sugar, salt).
  • Insoluble Materials: Sand and chalk powder do not dissolve in water(e.g., sand, chalk powder).
• Some liquids mix well with water, while others form separate layers (e.g., oil).

e. Floatation

• Definition: Some objects float or sink in water based on their density.
• Examples:
  • Floats: Plastic, wood, leaves.Sinks: Stones, metals.

f. Heaviness of Materials

• Heavy Materials: Have more mass (e.g., sand, pebbles).
• Light Materials: Have less mass (e.g., water).
• Objects can be compared based on mass.

g. Space and Volume

• Volume: The space a material takes up. Objects take up space.
  • For example, if your bag is on your seat, you can’t sit because it occupies the space.
  • Example: Water in different bottles shows different volumes -1L, 500mL.

Now you know many properties of materials, but not all materials have the same properties!

What is Matter?

• Matter: Anything that has mass and takes up space.
• Example: Water, sand, and even air are all types of matter.
  • Mass: The amount of matter in an object, measured in grams (g) and kilograms (kg).
  • Volume: The space matter occupies, measured in litres (L) and millilitres (mL).

All materials are types of matter used to make objects.

Grouping Matter

• Materials look and behave differently, so we group them based on their properties.
• Grouping helps us observe patterns and study materials better, just like we classify plants and animals.

Is Air Matter?

• Yes, air is also matter because it has mass and occupies space.

SI Units

• Mass: Kilogram (kg) is the SI unit.
• Volume: The SI unit is cubic metre (m³).
  • 1 m³ = 1000 L.
• Example:
• Write “7 kg” for 7 kilograms and “500 mL” for 500 millilitres.

Ancient Indian Classification (Ayurveda)

• Ayurveda describes physical matter using 20 opposite properties, such as:
  • guru (heavy) vs. laghu (light in weight)
  • manda (slow) vs. tīkṣhṇa (quick, fast)
  • uṣhṇa (hot) vs. hima (cold)
  • mṛidu (soft) vs. kaṭhina (hard)
  • sāndra (solid) vs. drava (liquid)

These properties help describe not only materials but also living things and the environment.

Chapter Summary:

• Grouping helps in organizing, studying, and choosing materials for specific purposes.
• Objects can be grouped by shape or material.
• Materials have properties like hardness, solubility, floatation, and transparency.
• Understanding material properties helps in practical applications, like selecting materials for specific uses.