Ch. 2.1 - Chemical Bonding

• covalent bonds: non polar = equal sharing, and polar = unequal sharing • ionic bonds: one donates and one receives • hydrogen bonds: between different molecules

• based on the sharing/donating/receiving of electrons so both end up with completed outer shells • sometimes electrons are shared equally (covalent) or unequally because one element attracts electrons more strongly (polar covalent)

• atoms attraction for shared electrons • if one atom in a bond is more electronegative then the other bond is polar -> one area will have a slight +. charge and the other is a slight -

in a constant tug of war

• electron stealing or donating • gives up electron -> positive ion • takes electron -> negative ion

form between slightly positive hydrogen of one molecule and slightly negative oxygen or nitrogen etc of another molecule

• universal solvent - dissolves more substances than any other chemical, especially gases and ions • no other natural substances that occur in quantity as liquids at the earth’s surface • can dissolve many other molecules, especially those held together by ionic or polar covalent bonds

attraction between hydrogen and oxygen of different water molecules

a liquid that is a mixture of two or more substances

dissolving agent - usually liquid (water=most versatile)

substance thats dissolved in a solution (often solid)

• philic=water loving - phobic=water fearing

• should only exist as a gas at earths temp • high heat capacity - takes a lot of heat to change the temp (need to break hydrogen bonds) • high viscosity and cohesion and adhesion - meniscus water strider • ice forms tetrahedral structure which holds water molecules far apart so ice is less dense • evaporates and freezes at much higher temps

temp/energy needed to raise 1g of water to 1 degree

• tendency of molecules of the same kind to stick together • much stronger for water than other liquids • water strider has evolved to take advantage of cohesion

total amount of energy associated with molecular movements

the intensity of heat

• oceans are relatively cold, but they contain 1000x more heat than the atmosphere • water moderates the temp of the earth

• heat is absorbed to break h-bonds and is released when they form requires much more heat than if there were no h-bonds • when h-bonds form (as when ice forms a lattice structure) heat is released • when sweat evaporates water is going from a liquid to a gas, this breaks the h-bonds holding it as a liquid. as h-bonds break they absorb heat, thus cooling your skin