add more waves notes, chem h20 notes

diff --git a/chem/water.md b/chem/water.md
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+# Water
+
+- <70% of Earth covered by water
+- polar, discrete molecular compound
+- latent heat - measured in kJ / mol or J / kg
+- fusion - solid to liquid (bonds between ice molecules must be broken)
+- vaporisation - liquid to gas
+- relatively high latent heat & heat capacity
+
+## Water cycle
+- clouds
+- rain
+- waterways
+- ocean
+- evaporation (sun)
+
+## Specific heat capacity
+- energy required to heat by one Kelvin
+- $Q=mc \Delta T$
+
+## Density
+- mass per volume (g / cm^3 or kg / m^3)
+- density of water depends on state
+- ice becomes less dense approaching $0^\circ$
+- water becomes less dense approaching $100^\circ$
+- maximum density at $4^\circ$
+
+## Conductivity
+- conductors have electrons which are free to move
+- water has covalent bonding (each atom needs one electron to be stable)
+- this means it has negligible conductance
+- slight conductance is due to self-ionisation
+
+## Hydrogen bonding
+- dispersion forces are weak (only three atoms)
+- H-bonding and covalent bonds hold water molecules together
+- electronegativities (H+, O-) attract H to O
+- since electrons are attracted to O, the other side of H atoms are free from -ve charge
+- +ve side of H atoms are attracted to -ve side of O atoms in other molecules
+- causes higher melting and boiling points, expansion when frozen (hexagonal structure), high latent heat, specific heat capacity, solvent properties
+
+## Solubility
+- "like dissolves like" - polar/non-polar substances
+- miscisble / immiscible
+- ionic crystals (salts) - polar, so soluble in water - "dissociation"
+- polar molecules may react to form ions (which may also dissolve)
+- other polar molecules may form hydrogen bonds
+- polar gases dissolve easily as well e.g. CO2 enables submarine photosynthesis
+- solubility is useful for living organisms (blood etc)
+- surfactants - polar + non-polar ends, dissolve in both oil + water
+
+## Measuring solubility
+- heterogeneous (mixtures) or homogeneous (solutions)
+- (un)saturated solution - maximum amount of solute for volume of solution
+- supersaturated solution - slow cooling of saturated solution
+- aqueous solutions - substance dissolved in water
+- most salts (ionic) are soluble in water to some extent
+- more soluble at higher temperatures
+- solubility measured in g / 100g H2O
+
+## Crystallisation
+- used to isolate substances based on $\Delta$ solubility in substances
+- can cause saturated or supersaturated solutions (unstable)
+- crystals precipitate out of (super)saturated solutions, can be collected by filtration
+- used to purify substances
+- $\Delta T$ can be substituted with pressure
+
+## Concentration
+- amount of solute per volume of solvent - e.g. g / L
+- relative terms - "concentrated" or "dilute"

diff --git a/physics/midyear.fdb_latexmk b/physics/midyear.fdb_latexmk
index 3b95bb6b0a6e4a1cc279c4a7aa352b1949283ccb..6f9b2aaf1bb0c2eee2d6d1c819cb77aaeee505a3 100644 (file)
--- a/physics/midyear.fdb_latexmk
+++ b/physics/midyear.fdb_latexmk
@@ -1,5 +1,5 @@
 # Fdb version 3
-["pdflatex"] 1531545115 "midyear.tex" "midyear.pdf" "midyear" 1531545116
+["pdflatex"] 1531545115 "midyear.tex" "midyear.pdf" "midyear" 1531896370
   "/mnt/andrew/graphics/ac-generator.png" 1529320281 28991 f74a831edcaed66632e709a6b2e2ebfd ""
   "/mnt/andrew/graphics/ac-motor.png" 1529313736 18626 d0f4943be26fdce44a4ce45ccb01633c ""
   "/mnt/andrew/graphics/banked-track.png" 1531025364 51228 cc5d8f3f8efb06a64aca4afabfd63eed ""
@@ -71,8 +71,8 @@
   "/var/lib/texmf/fonts/map/pdftex/updmap/pdftex.map" 1530607795 2586890 ddabbb88c498d59d5daa7919afb0a27f ""
   "/var/lib/texmf/web2c/pdftex/pdflatex.fmt" 1530607774 7906415 c2bc2a1e85cbebe301ae391211242f7e ""
   "midyear.aux" 1531545115 223 c9c8cc73e6c5d1c4bae220d8eb29b53c ""
-  "midyear.tex" 1531545115 7760 df61705a0ad9f9a0549b9ac5cd9a1da8 ""
+  "midyear.tex" 1531896360 7760 df61705a0ad9f9a0549b9ac5cd9a1da8 ""
   (generated)
-  "midyear.aux"
   "midyear.pdf"
   "midyear.log"
+  "midyear.aux"

diff --git a/physics/waves.md b/physics/waves.md
index 0b085c54916e158887f49f38f35fb53fdad2e629..8f94d828e04e1372b50051efee32206ea855d83c 100644 (file)
--- a/physics/waves.md
+++ b/physics/waves.md
@@ -90,6 +90,8 @@ $f = {nv \div 4l}\quad$ (frequency for $n_{th}$ harmonic at length $l$ and speed
 
 ## Light
 
+
+
 Newton - light as a particle
 - light speeds up as it travels through a solid medium