U2 AOS 1 Chapter 9 Flashcards
condensation
state change from gas to liquid (opposite to vapourisation)
group 16 hydride
Group 16 element covalently bonded to hydrogen, all group 16 hydrides are V-shaped
specific heat capacity definition
the amount of energy required to raise the temperature of 1g of a substance by 1 degree C
latent heat of vapourisation definition
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
transition of a substance between states
phase change
potable water
drinkable; low salt content, free from contaminants
brackish water (+ eg.)
more salinity than freshwater, less than seawater eg. swamps, lakes, estuaries
uses of water
solvent (polarity), coolant (heat absorption), means to convert thermal to mechanical energy
water vs potable water (statistics on earth)
more than 70% of Earth’s surface is water (97% salt, 3% fresh), vast majority is not drinkable
freshwater eg
eg. lakes, rivers, streams
water vapour eg.
air
What is the structure of water?
each water molecule can form up to 4 hydrogen bonds
specific heat capacity formula (+ constants)
q=mc∆T where heat capacity of water is 4.18J/g/C
mL to g
x 0.997
ice structure
less than water, molecules move slowly, form hydrogen bonds w/ 4 water molecules, tetrahedral lattice structure, molecules further apart
liquid water structure (vs ice)
more dense than ice, molecules move fast, form hydrogen bonds w/ 4 water molecules randomly, random arrangement, molecules closer together
latent heat formula (+ constant)
q=n x kJ/mol where LHV of water is 44.0kJ/mol
significance of thermal properties of water
- 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
Why does water have a high latent and specific heat?
strong IMFs, absorbs large amount of energy in bonds before it changes state or temp
Why does water act as a coolant?
high specific heat capacity, stores large amounts of energy before temp increases (efficient)
Why is water able to form 4 hydrogen bonds?
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
How does water’s high latent heat of vapourisation allow the temperature of water to remain stable?
in relation to ocean
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)
