Importance of these properties

1- They work on the cohesion of cell substances.

2- Slowing down losing water in plants' leaves through pores.

3- Some insects can walk on water due to the cohesion of the molecules on it surface (water has high surface tension)

5- Water density decreases under 4◦C

 Water expands when its temperature becomes less than 4◦C (instead of shrinking) , which decreases its density and makes it float (in frozen lakes, we find ice on their surfaces, while we find liquid water in their bottoms).

 This property is because of the hydrogen bonds between water molecules.

Importance of this property

 It enables living organisms to live in oceans and seas, without this property, all oceans and seas will turn into ice. By this property, only the surface of water freezes (which works as an insulator to prevent the rest of water from freezing).

6- The freezing point of water decreases if it has substances dissolved in it

 This property is very important for living organisms because water in organisms which are exposed to temperatures less than 0◦C doesn't freeze because it has some substances dissolved in it.

7- Water can turn into vapour in temperatures lower than boiling point (100◦C)

 Water vapour formed on the surfaces of oceans are carried by convention currents to cold atmosphere layers, which change it into clouds which provide living organisms with rain and water.

8- Water rise in capillary tubes

 Water has the ability to rise in capillary tubes without being pumped despite of gravity.

Importance

This property helps water transport from trees' roots to all its parts.

Polar molecule: A molecule which has a negative pole (atoms with molecular negative charges) and positive pole (atoms with positive charges).

Hydrogen bond: A bond between molecules containing hydrogen atoms by which negative hydrogen atoms of a molecule attract the positive oxygen atoms of another one.

Specific heat: The amount of heat required to increase the temp. of one gram of matter 1 Celsius degree

Surface tension: The cohesion of the molecules on the surface of a fluid to occupy the least possible volume.

Viscosity: The resistance of fluid to flowing.

1- Water is very important for living organisms

Because it plays an important role in all vital processes within living organisms.

2- Water molecules are polar

Because hydrogen atoms carry molecular negative charges, while oxygen atoms carry molecular positive charges. So water molecules have negative and positive poles.

3- Water has unique properties

Because of its polarity and hydrogen bonds between its molecules.

4- Water is regarded as "the general solvent".

Because so many substances dissolve in it due to the polarity of its molecules

5- Being water a polar solvent is very important to living organisms.

Because all the essential substances for living organisms (vitamin, salts, amine acids, gases, glucose) transport inside their bodies in the form of solutes dissolved in water, and these substances take part in metabolism reactions inside cells.

6- Water has the ability to ionize many molecules.

Because of the polarity of water molecules.

7- The ability of water to ionize many molecules is so important to living organisms.

Because it is essential for the occurrence of some chemical reactions inside living organisms.

8- Water has high specific heat.

Due to the hydrogen bonds between its molecules.

9- High specific heat of water is important to us.

Because:-

1- It helps living organisms have constant temperature which is essential for the vital processes occurring within their bodies, as cells contain lots of water to keep their temp. constant.

2- It provides living organisms with temperatures suitable for life on earth.

10- Waters of oceans absorb great amount of sunrays in the morning, and spreads them in atmosphere at night.

To keep the temperature of earth suitable for living organisms.

11- Water has low viscosity and high surface tension

Due to the hydrogen bonds between its molecules.

12- The low viscosity and high surface tension of water are important to us.

Because They work on the cohesion of cell substances and slowing down losing water in plants' leaves

13- Some insects can walk on water.

Due to the cohesion of the molecules on water surface, as water has high surface tension.

14- Water expands and its density decreases when its temperature becomes less than 4◦C

Due to the hydrogen bonds between its molecules.

15- Water expansion at temp. less than 4◦C is important to living organisms.

Because it enables living organisms to live in oceans and seas, as only the surface of water freezes (which works as an insulator to prevent the rest of water from freezing)

16- The property of the decrease of the freezing point of water which contains solutes in very important to living organisms.

Because water in organisms which are exposed to temperatures less than 0◦C doesn't freeze because it has substances dissolved in it.

17- The property of the vaporization of water at temperatures less than boiling points is very important to us.

Because water vapour which is formed on the surfaces of oceans are carried by convention currents to cold atmosphere layers, which change it into cloud which provide living organisms with rain and water.

18- The rise of water in capillary tubes is very important for plants and trees.

Because this property helps water transport from plants roots to all its parts.

1- Choose the correct answer

1- Close water molecules are attracted to each other by relatively low electric attraction called ……….. bond.

A- Hydrogen B- Ionic C- Covalent D- Peptide

2- The amount of heat required to increase the temp. of one gram of matter 1 Celsius degree is called ………..

A- Latent heat B- Specific heat C- Heat amount D- Work

3- Plants lose water by .......... process to decrease their temperature.

A- Sweating B- Transpiration C- Respiration D- Execration

4- Animals lose water to decrease their temperatures in the form of…….

A- Lymph B- Blood C- Sweat D- Juices

5- When the temp. of water becomes less than 4◦C, …………..

A- it expands B- it shrinks C- it doesn't change D- its density increases

6- When substances dissolve in water,………

A- its freezing point decreases

B- its freezing point increases

C- its boiling point decreases

D- Neither boiling point nor freezing point changes

2- Write the scientific term

1- A molecule which has a negative pole (atoms with molecular negative charges) and positive pole (atoms with positive charges).

2- A bond between molecules containing hydrogen atoms by which negative hydrogen atoms of a molecule attract the positive oxygen atoms of another one

3- The amount of heat required to increase the temp. of one gram of matter 1 Celsius degree

4- The cohesion of the molecules on the surface of a fluid to occupy the least possible volume

3- Write short notes about

1- Water polarity

2- Water rise in capillary tubes

1- Choose the correct answer

1- Hydrogen 4- Sweat

2- Specific heat 5- it expands

3- Transpiration 6- its freezing point decreases

2- Write the scientific term

1- Polar molecule

2- Hydrogen bonds

3- Specific heat

4- Surface tension