Water. Water is a very unusual compound; it is very common and is found in all three conditional states, solid (as ice), liquid ( as water) and gas (as water vapor). . How Much is There?. Approximately three-fourths of the earth is water. The Importance of Water
very common and is found in all three
conditional states, solid (as ice), liquid
(as water) and gas (as water vapor).
- Water is the most abundant substance in living systems, making up 70% or more of the weight of most organisms.
- Water is of critical importance in all physiological processes in body tissues.
The quantity of heat energy required to convert one gram of solid to liquid at the melting point.
7. Heat of vaporization: 540 cal/g.
The amount of heat energy required to convert of liquid to vapor at the boiling point.
Water freezes to form ice at 0ºC but its maximum density is at 4ºC (ice floats over water).
6. Formation of hydrates.
Hydrates: when water solutions are evaporated, the substances separate as crystals.
Crystals that contain water in their structure are called hydrates.
Oxygen atom attracts electrons towards it more than the hydrogen atoms.
Electrons moved closer to the oxygen will give the oxygen atom a slight negative charge while the hydrogen atoms would have a slight positive charge making the water molecule a Polar Molecule.Structure of Water Molecule
Oxygen atom of one water molecule will be attracted to a hydrogen atom of another water molecule.
This type of electrostatic attraction is called: Hydrogen Bond.Structure of Water Molecule
Because of charge difference, water molecules will stick together forming a hydrogen bond.
Cohesion is the force of attraction between molecules of the same substance.
Cohesion among water molecules plays a key role in the transport of water against gravity in plants
Adhesion is the force of attraction between molecules of different substances such as glass and water.
Adhesion holds the drops to the glass.
Water stabilizes air temperatures by absorbing heat from warmer air and releasing heat to cooler air.
Water can absorb or release relatively large amounts of heat with only a slight change in its own temperature.
or dissolve in water are described as
5) Both ground water and sea water contain dissolved and undissolved pollutants.
6) Lake and river water may appear clear but may
contain mud or bacteria and other micro-
organisms that are harmful to our body.Impurities Present in Water
The purification of water is necessary for removal of impurities and can be done by 4 methods:
Sedimentation and filtration
AerationPurification of Water
Distillation is a process of converting water to steam and then changing the steam back to water by condensing it.1. Distillation
Boiling for 15 minutes will kill any bacteria present in the water and makes it safe for drinking although it does not remove dissolved impurities.2. Boiling
Water is first allowed to stand in large reservoirs where most of the suspended dirt, clay and mud settle down. This process is called sedimentation.