From c89fa4d2edbb218a123b1279e49e7ba87feb6ecb Mon Sep 17 00:00:00 2001 From: Andrew Lorimer Date: Thu, 19 Jul 2018 10:26:36 +1000 Subject: [PATCH] add more waves notes, chem h20 notes --- chem/water.md | 70 +++++++++++++++++++++++++++++++++++++ physics/midyear.fdb_latexmk | 6 ++-- physics/waves.md | 2 ++ 3 files changed, 75 insertions(+), 3 deletions(-) create mode 100644 chem/water.md diff --git a/chem/water.md b/chem/water.md new file mode 100644 index 0000000..b664cb0 --- /dev/null +++ b/chem/water.md @@ -0,0 +1,70 @@ +# 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 3b95bb6..6f9b2aa 100644 --- 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 0b085c5..8f94d82 100644 --- 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 -- 2.43.2