2 pages report - Cardillac Desert book

Chemistry of water

Atoms - protons, neutrons, electrons Bonding

Hydrogen bond

Polar molecule

Hydration

Atomic Structure

Helium

Neon

Krypton

Argon

Xenon

Ionic. Ionic compounds are formed by the transfer of electrons. Elements with 1,2 or 3 outer electrons generally donate the electrons to other atom that is configured to accept them. In the formation of sodium chloride, for example, sodium gives up its outermost electron and becomes a positively charged ion, while chlorine takes on the electron and acquires a single negative charge:

Na + Cl --> Na+Cl-

The transfer of electrons results in an electrostatic force that binds the ions together to form the crystal of sodium chloride.

Halogens - red; Alkali Metals - purple

Covalent. Covalent compounds are formed by sharing of electrons rather than an actual transfer. Covalence accounts for the bonding of non-ionic compounds such as:

H2

Cl2

CH2=CH2

CH=CH

A special type of covalent bond called a coordinate covalent bond or dative bond results when all of the electrons of the bond are supplied by one of the atoms. For example, the production of ammonium ion: NH3

Ionic

covalent

Relative Bond Strength

______________________________________________

Covalent bond (between atoms) usually > 1000

Ionic bond (between atoms) 100

Van der Waals force

(between molecules) 1

Hydrogen bond 10

Heat Capacity - higher than solid or liquid other than Ammonia - special hydrogen bond

• moderates climate

• transports large amonts of heat

Latent Heat of Fusion (solid/liquid transition at 0˚C) - higher than any other substance other than ammonia

• Add 80 calories per gram to go from ice to water, likewise remove 80 per gram to go from water to ice

• when ice forms most of the energy lost is released to the atmosphere; ice absorbs large amounts of heat in melting. Keeps high-latitude water and atmosphere near freezing point all year!

Coriolis Force is an ‘Apparent Force’

Latent Heat of Vaporization (liquid/gas transition 100˚C) - higher than that of any other substance! 600 calories per gram

• regulates temperature of earth and living things - low latitude heat is transported to higher latitudes,

Thermal Expansion - pure water has a maximum density at 4˚C, the temperature at which maximum density occurs decreases as salinity increases.

• Freshwater and low salinity water remains unfrozen under ice

3.4 molecules4 molecules

Solvent Property - water can dissolve more substances than any other liquid (hydration)

• weathering and salinity of oceans

• medium for chemical reactions that control life

Surface Tension - higher than any other liquid

• controls the formation of droplets in atmosphere

What is the shape of a rain drop?

• bubbles in water

Physical States - only substance present as a gas, liquid, and solid within the temperature range at the earth’s surface

• moderates climate, changes albedo

• if no hydrogen bonds water would freeze at -90˚C and boil at -70˚C and all water on Earth would be gaseous

Continental Rocks and Soils are constantly being weathered by water and the salts are transported to the oceans.

However, it is thought that the concentration and composition of dissolved salts in the oceans has remained essentially unchanged for millions of years!

How is this possible?