हिंदी
Tamil Nadu Board of Secondary EducationTamil Nadu Primary School Class 4
पाठ्यपुस्तक उत्तर४२४४
अवधारणा स्पष्टीकरण७४
पाठ्यक्रम

Properties of substances

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Topics

  • Activity 1
  • Activity 2
  • Activity 3
  • Activity 4
  • Activity 5
  • Activity 6
  • Activity 7
  • Metals

Activity 1

To observe and understand the property of brittleness by applying pressure to various substances.

  • Apply pressure to each substance and observe the result.
  • Substances that break easily when pressure is applied are called brittle. This property is known as brittleness.

Brittleness

Activity 2

To understand how different materials offer resistance to an iron nail, demonstrating their hardness.

  • Try to pierce an iron nail through cardboard, wet mud, and wood, and observe how much effort is needed for each material.
  • The nail pierces wet mud easily, cardboard with some effort, and not wood. Materials with more resistance to penetration are harder. Hardness measures how much a material resists being pierced.

Hardness

Activity 3

To explore the elastic properties of different materials.

  • Stretch the rubber band and press the sponge, then release them.
  • The rubber band and sponge return to their original shape, showing elasticity.
  • Some substances change their shape when a force is applied to them but return to their original shape and size when the force is removed. This property is called elasticity.

Elasticity

Activity 4

To understand how different liquids flow on a sloping surface.

  • Place drops of water, honey, and gum on the inclined sheet and observe their flow.
  • Liquids flow downward due to gravity; the ease of flow depends on the fluidity of each liquid.

Fluidity

Activity 5

To compare the density of two substances with the same volume.

  • Weigh both blocks on a balance scale.
  • Substances with the same volume may have different weights due to differences in density; iron is heavier than wood.

Activity 6

To determine the solubility of different substances in different liquids.

  • Try dissolving salt, sand, and sugar in water and then in kerosene.
  • Solubility varies with the solvent; for instance, salt is soluble in water but not in kerosene.
  • The property of a substance that gets dissolved is called its solubility.

Solubility

Activity 7

To demonstrate the property of transparency by observing objects through various substances.

  • Gather glass, different types of plastic, clean water, air, and objects for observation. Place an object behind each material one at a time and attempt to view it from the other side. Record whether the object is visible through each substance.
  • When we look through a substance and see things from the other side, that substance is said to be transparent. This property of the substance is called transparency. Glass, some types of plastic, clean water and air are transparent substances.

Transparency

Metals:

Metals are materials like copper, gold, iron, and aluminium. These substances are shiny, strong, and can conduct heat and electricity well. 

  • Metals are found in the Earth’s crust. The Earth’s crust is the outermost layer of our planet. They exist naturally in forms called minerals. Minerals are like the ingredients that make up rocks.
  • To obtain metals, we need to dig up minerals from the ground, a process called mining. Once minerals are mined, they are processed to extract metals from them. This process might involve heating or treating the minerals with chemicals to remove the metal.

Uses of Metals in Daily Life:

  • Metals like iron and aluminium are used to construct buildings, bridges, and vehicles because of their strength.
  • Metals are good at conducting electricity and are perfect for electrical wiring and appliances.
  • Metals like gold and silver are used to make jewellery because they are attractive and can be shaped easily.
  • Many tools and kitchen utensils are made of metal because they can withstand heat and are durable.
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