Chapter 7.2 & 7.3: Solutions from 7.1, In a solution – solute: stuff dissolved – solvent: it’s dissolved in Called the universal solvent, because almost everything dissolves in water ( not because our bodies are mostly water or the Earth is 75% water) Water – Polar compound: oxygen keeps the electrons a little more than hydrogen does, so it has a little bit of charge on each end – “uneven distribution of electrons” … not equally shared, so has charge

Dissolving Process in water, the partial charge helps pull molecules apart, making more room for interactions between molecules breaking apart gives more surface area for interactions between molecules stirring/shaking moves molecules away, making more room for interactions between molecules heating makes molecules move faster so there’re more interactions between molecules

Hydrogen Bonding Because water is polar, it forms hydrogen bonds between atoms Not a bond within one molecule, e.g. between the hydrogen and oxygen A bond between 2 atoms…hydrogen of 1 water is attracted to oxygen of another because water is polar.

Nonpolar compounds no partial charges “electrons evenly distributed” … evenly spread out, so no charges e.g. oil Like Dissolves Like: – Things only dissolve in similar solvents, i.e. polar in polar and nonpolar in nonpolar.

Solubility and Concentration Solubility: maximum amount of solute that will dissolve at a particular temperature and pressure (quantitatively) – also how well it dissolves in something (qualitatively) – depends on the strength of attraction between atoms Concentration: actual amount dissolved – g solute/100mL solvent (1 mL isn’t a lot, so we use 100 mL) – a lot: concentrated – a little: dilute

Concentrations of solutions unsaturated: can hold more solute, holding less than the maximum amount at that temp. saturated: can not hold any more, holding the maximum amount at that temp. supersaturated: hold more than normal at that temp (make by heating, adding solute and then cooling) video: w w &feature=fvw &feature=fvw

Factors affecting solubility Temperature: as temp of solvent goes up, can hold more solid, but less gas Pressure: as pressure goes up, can hold more gas So…to dissolve more solid, increase temperature To dissolve more gas, increase pressure

Solubility Curves not in book show how much will dissolve at a certain temperature If you have a concentration on the line, it is saturated. It is holding the maximum it can at that temp

Solubility Curves If you have a concentration above the line, it either will not stay in solution, because it is holding more than the maximum it can at that temp. Or it will be supersaturated. If you have a concentration below the line, it is unsaturated. It is holding less than the maximum it can at that temp … you can still add more solute.

Solubility Curves Note how the line for a gas looks different … as temp goes up, the gas molecules move faster and do not stay in the solution. Sol. decreases as temp. increases