U2 AOS 1 Chapter 9

state change from gas to liquid (opposite to vapourisation)

Group 16 element covalently bonded to hydrogen, all group 16 hydrides are V-shaped

the amount of energy required to raise the temperature of 1g of a substance by 1 degree C

the amount of energy that needs to be absorbed by 1 mol of a substance to convert it from liquid to gaseous state at its boiling point

phase change

drinkable; low salt content, free from contaminants

more salinity than freshwater, less than seawater eg. swamps, lakes, estuaries

solvent (polarity), coolant (heat absorption), means to convert thermal to mechanical energy

more than 70% of Earth’s surface is water (97% salt, 3% fresh), vast majority is not drinkable

eg. lakes, rivers, streams

air

each water molecule can form up to 4 hydrogen bonds

q=mc∆T where heat capacity of water is 4.18J/g/C

x 0.997

less than water, molecules move slowly, form hydrogen bonds w/ 4 water molecules, tetrahedral lattice structure, molecules further apart

more dense than ice, molecules move fast, form hydrogen bonds w/ 4 water molecules randomly, random arrangement, molecules closer together

q=n x kJ/mol where LHV of water is 44.0kJ/mol

• heat is absorbed (coolant) • high specific heat temp ensures constant biological temp • SHC prevents solar energy raising temp of ocean - rising global temp combats thermal properties of water

strong IMFs, absorbs large amount of energy in bonds before it changes state or temp

high specific heat capacity, stores large amounts of energy before temp increases (efficient)

polar bonds between oxygen and two hydrogens water = oxygen (two partially negative lone pairs), two hydrogens (partially positive) opposite partial charges on seperate water molecules attract, 4 hydrogen bonds can be made

large amount of energy is removed from ocean when it evaporates allows heat to be released reducing the amount of heat stored in the water = maintaining stable, relatively cool temperature (like sweating)