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Social Sciences: Class 3 — Chapter 10: This World of Things

10.1 Let's Take a Look Around Us!

We begin by observing the classroom environment and identifying various objects around us. Understanding what these objects are made of helps us explore the materials in our world.

Classroom Observations

  • Classroom Objects: Tables, chairs, doors, windowpanes, blackboards, light bulbs, and electric switches.
  • Materials: These objects are made of different materials such as wood, metal, glass, and plastic.
10.2 Materials and Their Properties

Different objects are made of different materials based on their properties and uses.

Metals

  • Metals are materials carefully extracted from certain rocks and sediments called ore dug up from inside the Earth.
  • Common metals include iron, copper, aluminium, gold, silver, and mercury.
  • Alloys are mixtures of metals, such as steel, brass, and bronze.
  • Uses: Hinges, nails, and latches of doors are typically made of metals due to their strength.

Light Transmission: Transparent, Translucent, and Opaque

  • Transparent: Materials that you can see through clearly (e.g., most kinds of glass).
  • Opaque: Materials that you cannot see through at all (e.g., wood, metal, cardboard).
  • Translucent: Materials that are in-between, allowing you to see through them only partially (e.g., butter paper, thin colored plastic, frosted glass).

Sources of Materials

  • Wood: Comes from trees.
  • Glass: Mostly made of sand.
  • Metals: Extracted from ores found in the Earth.
  • Plastic: Made artificially, often from petroleum-based materials.

Physical Characteristics: Sound, Flexibility, and Suitability

  • Sound (Orchestra): Different materials produce distinct sounds when tapped (e.g., metal makes a sharp "ting-ting", wood makes a dull "thak-thak").
  • Flexibility: Wood is hard and rigid, making it suitable for tables. Fabric is soft and flexible, making it suitable for clothes and curtains.
  • Odd Pairs: Pairing objects with unsuitable materials highlights their properties (e.g., an umbrella made of paper would tear in the rain; walls cannot be made of water because it flows).
10.3 States of Matter: Solids, Liquids, and Gases

Objects and materials around us can be classified into three primary states based on whether they flow and keep their shape.

Three States of Matter

  • Solid: Things that do not change their shape easily (e.g., stones, bricks, wood, ice, spoons, bags).
  • Liquid: Things that do not keep their shape and can flow, but stay inside a container when poured (e.g., water, ink, honey).
  • Gas: Things that flow and do not stay in an open container, floating in and out (e.g., air, smoke, steam).
10.4 Natural vs. Artificial Materials

Materials can be grouped based on their origin.

Classification

  • Natural: Things that exist naturally in nature and are not made by humans. They can be alive (plants, animals) or non-alive (rocks, water, air, sand).
  • Artificial: Things that are made by people (e.g., clothes, shoes, plastic toys, tables).
10.5 Let Us Reflect

Review exercises and discussion questions to consolidate learning.