Chapter 1: Water

1.1 Importance of Water for Life

From the article, the words associated with water, as discussed in class, are listed below.

Water

1. Boiling point of 100˚C

2. Can act as a shield

3. DNA

4. Dissolves minerals

5. Electron hog

6. Forms crystal lattice

7. Hydrogen bond

8. Less dense in solid form (i.e. ice)

9. High specific latent heat

10. H2O is a polar molecule

11. Absorbs UV rays

12. Dipole

13. Oxygen covalent bond

14. Indicator of life

15. Large (i.e. large enough to insure that water in cells will neither freeze nor boil off) range of temperature. Doesn’t boil/freeze easily.

16. Transporting molecules

17. Density decreases when frozen

18. Versatile and unique

19. Maintains stable climate on Earth

20. Most abundant liquid in the universe

21. Pond will not freeze entirely so life forms can survive

Hence, I will be touching on the main roles of water on Earth.

Water is needed for:

1. Replication

Water allows organic compounds to react in ways that ultimately allow replication.

2. Metabolism for life

Metabolism is the sum total of anabolism and catabolism. In anabolism, water is removed from molecules for the growth of larger molecules while in catabolism, water is used to break bonds for the generation of smaller molecules. 

3. Photosynthesis in plants

During photosynthesis, carbon dioxide and water are needed for the production of glucose.

4. Continuity of underwater ecosystems

Fishes and marine mammals, and plants live and grow in the water respectively. Some of these animals are the foundation of the ocean food chain while the plants provide aquatic vertebrates with oxygen to survive.

5. Agriculture

Water is used for irrigation in agriculture. 

6. Drinking

The human body contains 55%-78% water. To function properly, the body requires at least two liters of water per day to avoid dehydration. 

7. Washing

Many industrial processes rely on reactions using chemicals dissolved in water, suspension of solids in water slurries or using water to dissolve and extract substances. 

8. Chemical uses

Water is widely used in chemical reactions as a solvent or reactant and less commonly as a solute or catalyst.

9. Heat exchange

Water and steam are used as heat transfer fluids in diverse heat exchange systems, due to its availability and high heat capacity, both as a coolant and for heating.

10. Fire extinction

Water has a high heat of vaporization and is relatively inert, which makes it a good fire extinguishing fluid. Hence, the evaporation of water carries heat away from the fire.

11. Recreation

Humans use water for recreational purposes, exercising and sports. Lakesides, beaches and water parks are also popular places for people to go to relax. Besides that, some keep life in aquariums or ponds for show, fun, and companionship.

12. Industrial applications

Hydroelectric power comes from water driving a water turbine connected to a generator. Besides that, pressurized water is used in water blasting and water jet cutters. Also, very high pressure water guns are used for precise cutting. In addition, water is used in the cooling of machinery to prevent over-heating.

13. Food Processing

The level of water activity affects bacterial growth while water hardness affects the quality and sanitation of a product as well as its pH balance. Besides that, some cooking methods involve the immersing of food in water or steam. Water is also used for dishwashing.

Wikipedia (25-03-2011 16:11) Water. Retrieved March 29 2011, from http://en.wikipedia.org/wiki/Water

Nurul Azirah Binte Johari (11)

Cloud Forming Exercise & Linking Wind and Precipitation to Deserts

New concept learnt: Condensation nuclei

A nucleus is a central body around which something may grow, collect, or concentrate. A condensation nucleus is formed when water vapour in the air clings to microscopic, atmospheric particles (usually dust), and then condenses to form water droplets. 

Linking Wind and Precipitation to Deserts


Overview of global wind patterns/ action
          

Circulation of air over the Earth's surface is due to the differential heating between the equatorial and Polar Regions, and the fact that hot air being lighter rises above the cold air. Hence, air heated at the equator would rise and reach the Polar regions, where the chilled air would descend to the equatorial regions. Rotation of the earth creates a deflecting force on the winds, known as Coriolis Effect. The Coriolis Effect influences the wind by deflecting it to the right in the northern hemisphere, and to the left in the southern hemisphere.

To see a sequence of weather satellite images showing the actual wind direction, go to Exploring Earth.

Deserts

About one- fifth of Earth's land surface is desert. A desert is a geological region that receives little precipitation. Generally, deserts are defined as areas that receive an average annual precipitation of less than 250mm (25.4cm). Deserts usually have extreme temperature range.

1. Wind and high temperatures

Trade winds heat up as they approach the Equator. These dry winds dissipate cloud cover, allowing more sunlight to heat the land. Most of the major deserts (E.g. Sahara Desert) lie in areas crossed by the trade winds. The temperature can go as high as 57 degree Celsius.

     2.   Orographic precipitation and arid lands

Rain shadow deserts are formed because tall mountain ranges prevent moisture- rich clouds from reaching areas on the lee of the range. Air masses lose much of its moisture as they move over a mountain range. A desert is then formed on the lee side of the range.

      3.   Convectional and frontal precipitation

Convectional and frontal precipitation is more common in humid regions than desert regions because humid air is lighter than dry, desert air. Hence, it rises due to buoyancy, and leads to heavy precipitation during most part of the year.

Nur Shahanaz (10)