Structure and Properties Water

Water around us Water is everywhere. Most abundant molecule in living things. 2 WATER COVERS MORE THAN THE ¾ OF EARTH’S SURFACE ARE COVERING BY WATER

Water around us 3 WATER CONSTITUTES MORE THAN THE 70% OF HUMAN BODY 72%

Chemistry of Water Water has unique life- supporting properties like: Lower density in solid state than in liquid phase Cohesion Adhesion Capillary action How does its structure contribute to these properties? Watch this to answer this question. Chemistry of Water

Properties of Water Hydrogen Bonds Polarity causes water molecules to attract each other like magnets H (+) attracts O (-) forming a hydrogen bond Gives water special properties

Properties of Water Lower density of ice than liquid water Since ice is less dense than the water, bodies of water freeze from the top to the bottom. Provides insulation to the water under the ice, preventing all the water from freezing. This allows life to continue under the ice, provided there is sufficient nutrients. There are fewer molecules in the same space of ice than in liquid water.

Properties of Water Cohesion and Surface Tension The cohesive forces between molecules down into a liquid are shared with all neighboring molecules. Molecules on the surface have no neighboring molecules above, and so exhibit stronger intermolecular attractive forces upon their nearest neighbors on the surface called surface tension.

Properties of Water Cohesion and Surface Tension Because of the natural cohesive forces between water molecules and the fact that surface molecules have a surface tension, without a container, water forms spheres Little insects can freely run along the surface of a pond. They are supported by the high surface tension.

Properties of Water Adhesion Adhesion- attraction between the water the straw surface – resulting in a curved surface (meniscus) Meniscus

Properties of Water Capillary Action Capillarity action- Adhesion between water molecules and the walls of the tubes helps resist the downward pull of gravity on the water.

Properties of Water Temperature Moderation Because of hydrogen bonding, water has a better ability to resist temperature changes than most other substances.  It allows the body’s temperature control, avoid drastic changes of temperature that affect aquatic species, and explains the differences of temperatures between coastal and continental places. Effect of large specific heat capacity of water