Solids, Liquids and Gases Science Grade 3 | Orchids
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Forms of Matter

Concept: Solids, Liquids and Gases

Matter:

A matter is anything that possesses volume and weight and occupies space.

  • A matter has a definite mass.
  • It can be soluble or insoluble in water.
  • Different things are made using one or more forms of matter.
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Atoms and molecules:

  • Matter is made of very minute particles invisible to our eyes, called atoms.
  • Atoms tend to move or vibrate.
  • Two or more atoms strongly bond together and form bigger particles called molecules.
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Forms of matter:

Matters are present in three main forms—

  1. Solid:
    • Solids have a specific weight, mass and definite shape.
    • These are visible and can be held.
    • A solid has a definite shape because its molecules are strongly held together.

    Example: Rubik’s cube, scale, helmet, etc.

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  2. Liquid:
    • A liquid can flow freely but has a definite mass.
    • The molecules of liquids are loosely held. Therefore, liquids are fluid in nature and can be poured.
    • They take the shape of the container in which they are poured.
    • Liquids do not have a fixed shape but have a fixed volume.
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    Example: Water, oil, petrol, diesel, etc.

  3. Gas:
    • A gas does not have a specific shape and can flow freely in all directions.
    • Gases feel lighter than solids and liquids as the molecules of gas are free to move in any direction.
    • The atoms and molecules are not orderly arranged in gases.
    • Gases do not have a fixed size, shape, or volume.
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    Example: Oxygen, carbon dioxide, hydrogen, helium.

Changes in the forms of matter:

  • Solids, liquids and gases can interchange among themselves due to factors like temperature and pressure.
  • The conversion of a liquid to a gas when heated is called evaporation.

    Example: Change of liquid water to water vapour.

  • The conversion of a gas to a liquid when cooled is called condensation.
  • Example: Formation of dew.

  • The conversion of a liquid to a solid is called solidification.
  • Example: Water changing into ice.

  • The conversion of a solid to a liquid due to the application of heat is called melting.
  • Example: Ice cubes changing into water

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Water cycle:

  • The heat from the sunlight changes water from any water body into water vapour.
  • The water vapour is lighter than the liquid water, due to which it moves in the upper layers of air.
  • The air filled with water vapour reaches heights where the temperature is lower than the Earth’s surface, which condenses to form liquid water.
  • The condensed water then falls on the Earth as rain, called precipitation.
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Uses of matter:

  1. Uses of solids:
    • Solid wax is used in candles, crayons, etc.
    • Solid water, i.e., ice, is used to preserve the food items and in refreshing juices and drinks.
    • The pen, paper, pencil, bat, ball, cupboard and many things around us are solids.
  2. Uses of liquids:
    • Liquid water is used for drinking, cooking, washing, etc.
    • Liquid fuels such as petrol and diesel need to run the vehicles.
    • We use liquid oil in diyas.
    • Cooking oil is an essential part of our diet.
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  3. Uses of gases:
    • Oxygen helps in burning.
    • Animals use oxygen to breathe, whereas plants use carbon dioxide to make food.
    • The party balloons are filled with helium gas.
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Mixtures of different forms:

  • A combination of two or more substances of the same or different states is called a mixture.
  • We often use mixtures of solids, liquids and gases.

Example:

Mixture Solid Liquid Gas
Vapour -- Water droplets Air
Deodorant -- Chemical droplets Gas
Syrup Sugar Water --
Smoke Soot particles -- Air
Cream Chemicals Oil --

New Words:

Mass: The quantity of matter present in an object.

Soot: A black powdery substance produced from burning that settles on any surface.

Pressure: Measuring how much force is acting over an area.


Did You Know?

  • The air we breathe is composed of gases like nitrogen, oxygen, carbon dioxide, water vapour, etc.
  • The snow on the mountain can directly convert into water vapour without melting into liquid water first.
  • Fire is nothing but a mixture of hot gases.
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