Water

Chemistry of Life

Water

Periodic Table

Rare Gases

Elements of Life

Rare gases - which are shown on the right column of periodic table- are decisive

Rare gases don’t need to react with other elements because they have enough elements on their
orbits. That’s why we say about them “decisive”

If an element can have sufficient number of electrons it gets energetically stable

Every elements of life -except rare gases- want to have sufficient number of electrons on their
orbits

Every elements of life want to be decisive and energetically stable

Hydrogen & Helium

Elements of Water Molecule

Hydrogen

Oxygen

Oxygen

tetrahedral shape
electronegative

Water

Water

Water

Water has two elements: oxygen and hydrogen

Oxygen has 8 protons in its nucleus so it needs to have totally 8 electrons on its orbit to become
more stable.

Hydrogen has just one proton in its nucleus so it has just one electron on its orbit

A pole that oxygen has 2 pairs of electrons is called as partially negative charge

A pole that oxygen bind with hydrogens is called as partially positive charge

Water

The most stable arrangement is the one that puts them farthest apart from each other: a
tetrahedrone, with the O-H bonds forming two out of the four “legs”. The lone pairs are slightly more repulsive than the bond electrons, so the angle between the O-H bonds is slightly less than the 109 degrees (of a perfect tetrahedron), around 104.5 degrees

Because oxygen is more electronegative than hydrogen the O atoms hogs electrons and keep them away from the H atoms. This gives the oxygen end of the water molecule a partial negative charge, while the hydrogen end has a partial positive charge. Water is classified as a polar molecule because of its polar covalent bonds and its bent shape

Properties of Water

The attraction between partially positive charge of a water molecule and partially negative charge of other water molecule is called hydrogen bond

Cohesion

Fluid nature

Specific heat

Heat of vaporization

Temperature regulation

Density of water

Surface tension

Adhesion

Good solvent

Adhesion

Silicon

less electronegative than hydrogen

Adhesion

Surface Tension

Water as a good solvent

Water’s High Specific Heat

●The specific heat of a substance is defined as the amount of heat that must be absorbed or lost for 1gr of that substance to change its temperature by 1 ℃

●Water’s specific heat is 1 cal/g.℃. It means that we need heat of 1 cal to make changes of water’s temperatures by 1 ℃

●Alcohol’s specific heat is 0,6 cal / g.℃. It means that we need heat of 0,6 cal to
increase/decrease the alcohol’s temperature by 1 ℃

●Water’s specific heat is generally more higher than other matters in the nature. It means that we need much more energy to make changes of water’s temperatures in comparison with the other matters.

Moderation of Temperature

●Balancing of temperature in living bodies or in the atmosphere can be allowed as a result of water’s high specific temperature

●How much ever the earth takes sunlights directly, the temperature of the atmosphere
changes gradually. The atmosphere has %21 of oxygen

●How much ever the living bodies take heat from any factors, the inner temperature
changes gradually.

Floating of Ice on Liquid Water

●Water’s solid form is less dense than the liquid form

●Above 4 ℃, water behaves like other molecules. It expands as it warms, contracts as it cools.

●Water reaches to the highest density at the temperature of 4 ℃. At that point, the
distance between the water molecules becomes minimum. Water molecules are located at the closest points into each other.

●Under the temperature of 4 ℃, water’s behaviours change. It expands as it cools, it contracts as it warms.

●In comparison, water’s density at 0 ℃ is less than the density at 4 ℃

●The ability of ice to float due to its less density is very important factor in the
suitability of the environment for life in water (lake, sea, ocean etc.)

●So many living species can have opportunity to survive