Hemangi Borole Roll No.:- 72

Water is one of the most precious resource on earth and is necessary for all living beings. Water is used for different purposes. Water

About 71% of Earth is covered by water

Properties of Water Pure Water is colourless. Pure water is Odourless. Pure water is tasteless

Water exits in liquid, solid and gaseous state Water makes up 55% to 78% of the human body.

THE RELATION BETWEEN VOLUME AND MASS:  The mass of a unit volume of a substance is called the density of the substance. mass  Density = Volume  Mass is measured in grams and volume in cubic centimetres.  Hence, the unit of density is grams per cubic centimeters or g/cc.  One litre of water has a mass of 1 kg. Hence, the density of water is

1kg  Density of water = 1 l 1000g = 1000cc = 1 g/cc  Hence density of water is 1 g/cc.  As water freezes, that is, as it changes into solid, its volume increases.  Thus, its density decreases. That is why ice floats on water.

VIDEO

Salinity of water :  As water flows, salts from the soil dissolve in it. Rivers, streams, rivulets all flow into sea.  Hence, the water of the sea becomes salty.  Thus, the quantity of salts in the sea goes on increasing.  At the same time water in the sea is continually evaporating.  This results in the increase in the concentration of salt in the water.  It is about 35 grams per litre. Hence, the density of sea water is more than that of ordinary water. That makes it easier to swim in sea water.

The Dead Sea :  The sea on the borders of Israel and Jordan, the is, the Middle East, is called the Dead Sea. the river Jordan flows into it.  Other small streams, brooks also flow into it.  The level of this sea is as much as 396m below sea level of and there is no outlet for the water.  Besides, the temperature causes the water to evaporate all the time.  The water of the sea contains 23% to 25% salts in the Dead Sea water are mainly potassium and magnesium chloride and calcium chloride and bromide.

 No aquatic life can survive in this saline water. That is why it is called the dead Sea.  Naturally, with so much salt content the density of the water of the Dead Sea is much greater than normal water and there is no danger of drowning in it.  The plimsoll line : to indicate how much a ship can be loaded a line is marked on the ship’s side especially on cargo ship. It is called the Plimsoll line.  Legally, a ship may be loaded only till the Plimsoll line is visible above the level of the sea

Salinity of water Video

Solubility of water  What happens when we add sugar to water and stir it?  Small particles of sugar spread out in the water.  Gradually, they become smaller and smaller and disappear completely in the water.  We say that the sugar has dissolved in the water.

 The substance that dissolves is called the solute.  The substance in which the solute dissolves is called the solvent.  When the solute and solvent are completely mixed in each other we get a solution.  In the above example, sugar is the solute, water the solvent and the sweet water is the solution.  Because many substances dissolve in water, it is called a universal solvent.  Chemically, water is a neutral substance. This property makes water an ideal medium for most chemical reactions.

Solute + Solvent = Solution

1)What is a solute? 2)What is a solvent? 3)What is a solution? 4)Why water called universal solvent? 5)What is meant by water is chemically neutral ?

Application : 1)How are ice berg formed? 2)Why is it easy to swim inn dead sea ? 3)Why is water an ideal medium for chemical reactions? 4)What is relation between mass & volume of a substance? 5)What is plimsoll line?