5. Solids/Liquids/Gases - States of Matter chapter 12. Sometimes a solid becomes a gas without first passing through the liquid state. Such a process is called sublimation, eg. ‘dry ice’(CO 2 ) Above -78 o C, sublimes to the gas without melting
5. Solids/Liquids/Gases - States of Matter
Sometimes a solid becomes a gas without first passing through the liquid state.
Such a process is called sublimation, eg. ‘dry ice’(CO2)
Above -78oC, sublimes to the gas without melting
**Can cause extreme frostbite
Dry ice pellets in a balloon sublime
Chemical particles absorb heat and leave the orderly crystal lattice for greater ‘freedom of movement’ in the liquid
High energy molecules ‘escape’ from liquid and evaporate/vaporize.
Boiling Points (Bp) at 1 Atm pressure
GasFormulaBp.(oC, 1 atm.)
Water Ammonia Chlorine Methane Oxygen Fluorine Nitrogen Hydrogen Helium
H2O NH3 Cl2 CH4 O2 F2 N2 H2 He
+100 -33 -35 -164 -183 -188 -196 -259 -269
Mp & Bp of Some Common Substances
Vinegar Window cleaner Citrus fruit Solvent Beer/wine/etc Jewelry Fuel for BBQs Table salt Lye Table sugar Paint remover
118 –33 dec. 77 78 3080-42 1413 1390 dec. 111
Acetic acid Ammonia Citric acid Ethyl acetate Ethyl alcohol Gold Propane Sodium chloride Sodium hydroxide Sucrose Toluene
17 -78 153 -84 -117 1064 -190 801 318 185 -95
Increase Pressure and Decrease Volume
The Kelvin or absolute temperature scale (T) begins 273o below the Celsius zero
(-273oC), at absolute zero.
To convert oC to Kelvin, add 273
In Belfast NI
Inhale - Partial pressure of O2 increases in lungs and forces more O2 into blood to be taken to tissues.
Tissues - partial pressure of O2 is low thus O2 will enter the tissue from blood; but pressure of CO2 is high thus forcing CO2 into blood to return to lungs.
Exhale - partial pressure drops and CO2 escapes.
also: ‘decreased oxygen’ at high altitudes
‘excess gases’ in the blood (the ‘bends’)during deep-ocean diving
The atmospheric pressure at any point on the earth’s surface or above it is the pressure generated by the combined weight of all the atmospheric gases above that point. ( =14.7lb/sq.in.)
Composition of dry air:
Nitrogen - 78.1%, Oxygen - 20.9%,
Argon - 0.9%, CO2 and others ~ 0.1%
Exhale: Nitrogen - 74.9%, Oxygen - 15.3%,
Water - 6.1%, Carbon dioxide - 3.7%
Gas Laws in the Real World
ie.opening a can of pop/beer
1. High pressure of CO2 in sealed container causes extra CO2 to dissolve. (Henry’s Law)
2. When cap is removed the pressure drops to atmospheric causing gases to expand and escape. (Boyle’s Law)
3.. With drop in partial pressure above liquid, the solubility of CO2 in the drink also drops, more CO2 escapes and the drink goes flat! (Henry’s Law)
also: bicycle/car tires, balloons, gas line explosions