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SS2 Chemistry Third Term: WATER

Topic: Water 

Content 

  • Sources of Water
  • Types of Water
  • Water Pollution
  • Uses of Water

Introduction

We live on a planet that is dominated by water. More than 70% of the Earth’s surface is covered with this simple molecule. Scientists estimate that the hydrosphere contains about 1.36 billion cubic kilometers of this substance mostly in the form of a liquid (water) that occupies topographic depressions on the Earth. Water is also essential for life. Water is the major constituent of almost all life forms. Most animals and plants contain more than 60% water by volume. Without water life would probably never have developed on our planet.

Water has a very simple atomic structure. This structure consists of two hydrogen atoms bonded to one oxygen atom. The nature of the atomic structure of water causes its molecules to have unique electrochemical properties. The hydrogen side of the water molecule has a slight positive charge. On the other side of the molecule a negative charge exists. This molecular polarity causes water to be a powerful solvent and is responsible for its strong surface tension

Water Cycle

The Water Cycle (also known as the hydrologic cycle) is the journey water takes as it circulates from the land to the sky and back again.

water polution

The Sun’s heat provides energy to evaporate water from the Earth’s surface (oceans, lakes, etc.). Plants also lose water to the air (this is called transpiration). The water vapour eventually condenses, forming tiny droplets in clouds. When the clouds meet cool air over land, precipitation (rain, sleet, or snow) is triggered, and water returns to the land (or sea). Some of the precipitation soaks into the ground. Some of the underground water is trapped between rock or clay layers; this is called groundwater. But most of the water flows downhill as runoff (underground), eventually returning to the seas as slightly salty water.

Sources of Water

  • Rain water
  • Spring water
  • Well water
  • River water
  • Lake water
  • Tap water
  • Sea water

Types of Natural Water

There are four major types of natural water:

Rain Water: This is the purest form of natural water because it is formed as a result of the condensation of water vapour in the atmosphere. Rain water contains small impurities like gases such as CO2 from the air and also dust particles present in the air. Dissolved oxygen and nitrogen will always be present in rain water.

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