Importance of water

 TOPIC#3   BIOLOGICAL IMPORTANCE OF WATER

INTRODUCTION

   Water is essential for life.It is an inorganic compound.Everything on earth is made up of water.ALLAH ALMIGHTY has created everything from water.70% of earth surface is consist of water in which 97% of water is present in ocean which is salty and not suitable for humans because it cause kidney infection.and remaining 3% is fresh water(2% ice caps and 1% land water) which are suitable for drinking.

The cell protoplasm also contain 70-90% water  which is very important for normal function of protoplasm.Some important properties of water are discussed below;

1-Polar nature:

  Water is polar molecule it means it have positive and negative charge.

Water formula is H2O in which H is partially positive while O is partially negative.

O is partially negative due to excess of electron because it attract electrons from Hydrogen due to which hydrogen become electron defecient and positive charge comes on it.

Water molecules are attached to each other by hydrogen bond meanwhile hydrogen bond is weaker than covalent bond but still intact water molecule with each other.

Due to this polar nature water is called as universal solvent because it dissolves every kind of solutes.

2-Universal solvent:

   Due to this polar nature water dissolves every kind of solute polar and non polar therefore called as Universal solvent.

This nature facilates chemical reactions inside and outside of cell.

Water provides medium for most chemical reactions.

For example:

      When we add potassium chloride to water its positive end make bond with chlorine which is electronegative while potassium which is electropositive make bond with negative end of water oxygen and thus potassium chloride dissolves in water.

Due to this property the minerals from soil are absorbed by plants.

3-Cohesive and adhesive forces of water:

             water molecules attached with each other and donot seperate from each other because they have hydrogen bonding.

The force between water molecules are called as COHESIVE FORCE.

The force between water and the surface in which it moves called as ADHESIVE FORCE.

Due to these forces the water moves in plants from soil to ariel parts of plants.

4-High specific heat and high heat of vaporization:

The amount of heat required to rise temperature of water by one degree centigrade is called SPECIFIC HEAT .The water have high specific heat due to this property the water absorb large heat with little change in temperature and also its temperature rises slowly as compared to other liquids.Due to this property the internal temperature and condition of body remain sterile.

The amount of heat required to convert one gram of water into vapour is called HEAT OF VAPORIZATION.Water has high heat of vaporization.Due to this property animals and plants  get rid of excess heat during sweating and transpiration.

Water freezing point is 0 degree centigrade while boiling point is 100 Degree centigrade it is beacuse of presence of hydrogen bond in the absence of hydrogen bond the water freezing point is -100 degree centigrade while boiling point is -80.

5-Water expand at low temprature:

 Water is the only liquid which shows a unique property it become expands when it freezing point comes because it molecules acquires hexagonal structure and volumes increases because empty space creates in it.

Due to this property during winter in rivers and seas the thin layer of ice act as insulator layer to protect aquatic life from freezing .

6-Ionization of water:

  Water molecules ionization is very low only few molecules out of thousands molecules of water ionize into hydrogen ion and hydroxyl ion.

20-25 molecules out 10,000 molecules ionize.

The precense of ions is important for normal functions of Enzymes.

IMPORTANT MCQS IN THIS TOPIC

1- Water is _in nature.

Answer: POLAR

2- Water has high density at _ temperature:

Answer: 4  DEGREE CENTIGRADE 

3-Water has high volume at _Temperature:

Answer: 0 degree centigrade

4-The water is universal solvent because of which property:

Answer:  POLAR NATURE

5-Protoplasm have_% of water:

Answer:70-90

6-Plants picks minerals from the soil with help of _water property:

Answer:   POLAR NATURE

7-_Property of water is important for normal enzymes function:

Answer:  IONIZATION

8-The _force have hydrogen bond among them:

Answer:  COHESIVE

9-Hydrogen bond is _than Covalent bond:

Answer: WEAKER

10-Water specific heat is:

Answer: 4.18 JOULE

11-1 calorie is equal to _:

Answer: 4.18 JOULE

12-The temperature of water rises and falls more slowly because of which property:

Answer: HIGH SPECIFIC HEAT

13-The internal temprature of body maintain because of which property of water:

Answer: HIGH SPECIFIC HEAT

14-Water boiling point is:

Answer: 100 DEGREE CENTIGRADE

15-Water volume increases by _when temperature become reaches freezing point:

Answer: 9%

16-In absence of hydrogen bond in water the water freezing point is:

Answer: -100 DEGREE CENTIGRADE

17-Water has _surface tension:

Answer: HIGH

18-out of 10,000 molecules of water_ molecules ionize :

Answer: 20-25

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