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The ocean planet properties of water - Coggle Diagram
The ocean planet properties of water
Special properties of water
Three states
only element on Earth found naturally in all 3 states solid, liquid and gas.
Cohesion
Water’s polar bonding property causes it to attract other water molecules to itself resulting in the quality of cohesion. Water has the highest cohesion of any of the
non-metallic liquids. We can observe cohesion in nature when droplets are formed.
Surface tension
Cohesion results in the water molecules on an undisturbed surface being attracted to
each other more strongly than the other water molecules below the surface. This results in an elastic skin-like layer on the water surface called surface tension. This high level of surface tension allows certain insects such as mosquitoes or pond skaters to walk on a still water surface. Surface tension results in the tendency of a water droplet to take on the least possible surface area. This is referred to as a beading up quality. It can be observed as a water droplet rolls down a leaf or on a piece of glass or greaseproof paper.
Viscosity
Water can be stirred and poured easily as it has very little resistance to movement or to internal friction as a result of its molecular make-up. It has very little friction when it
is in motion. This quality is called viscosity, the ease with which a liquid pours or flows. Viscosity is influenced by temperature. Syrup at room temperature has a high viscosity, but when heated the viscosity increases. Although it has a lower viscosity than syrup, the cohesion of water molecules results in a slower flow of water than some other liquids such as ethanol.
Solvent
Water is called the universal solvent as water molecules are good solvents and more substances can dissolve in water than in any other substance on Earth. Salt or sugar are substances which easily dissolve in water and are called hydrophilic. Hydrophilic substances are polar because their polarity is stronger than the cohesive forces of the Hydrogen bonds between the water molecules. Conversely, there are other substances which are not strong enough to break the cohesive forces of the Hydrogen bonding between water molecules. Such substances do not dissolve in water and are called hydrophobic. They do not have charged poles and are thus non-polar. These substances are ‘pushed out’ of the water by the water’s cohesive forces. So, even though water may be called the universal solvent, it does not dissolve all substances.
Transparency
Water is a transparent substance. It allows light to penetrate to considerable depths. This means that plants in shallower water can perform photosynthesis even when submerged.
Incompressibility
Most liquids found on Earth cannot be compressed. Water is no exception, and is almost incompressible, unlike a Styrofoam cup or a wetsuit on a diver which, when taken down to a depth, is crushed by the water pressure. The quality of incompressibility gives water a capacity to function as a hydraulic fluid in mechanical appliances.
Salinity
Salinity refers to the amount of salt dissolved in a body of water. All salts in the ocean have originated from the land either as run off or as dissolved from sub marine volcanic activity. Over time, precipitation that has run off continents has
carried dissolved salts into the ocean. Dissolved salts also enter the ocean from volcanic activity below the surface. Sea water has an average salinity of 35 g of salt per cm3. Salinity is an important property of water for marine biologists and oceanographers.
At the South Pole the salinity of the ocean increases when Antarctica’s ice shelf forms. In summer, when the Antarctic Shelf melts fresh water is released into the ocean where the salinity decreases.
Density
There are several factors that influence the density of water. These are mainly temperature, pressure and salinity. The effect of pressure on density is small, but an increase in salinity increases water density. The density of water increases marginally as the water temperature decreases. The maximum density of pure water (1 g/cm3 ) is reached at 4 °C. Remember that ice is less dense than liquid water, and therefore floats on water, because less than air, and a moist mixture
of water vapour and air is less dense than dry air.
Pressure- the difference between air and water pressure
Both air and water exert pressure: on land, air pressure changes very little with vertical movement but water pressure changes rapidly. Air density gradually increases from least dense at the outer edge of Earth’s atmosphere to most dense at Earth’s surface. One atmosphere (atm) is the
average pressure on Earth’s surface measured at sea level. However, below sea level the pressure exerted by water increases by one atmosphere for every 10 meters of depth. Seawater is about 800 times denser than air. So, a column of seawater 10 m deep exerts the same amount of pressure as the entire ±500 km layer of air above Earth’s surface.