SWBAT summarize what causes surface tension in water.

SWBAT define solution, solute, solvent and polar molecule.

SWBAT summarize the steps of dissolving a substance.

SWBAT percent composition problems. SWBAT describe solubility and be able to

interpret a solubility curve. SWBAT describe why water is the

universal solvent.

Surface Tension: of a liquid results from an imbalance of intermolecular attractive forces, the cohesive forces between molecules:› A molecule in the bulk liquid

experiences cohesive forces with other liquid molecules in all directions.

› A molecule at the surface of a liquid experiences only net inward cohesive forces.

Surface Tension: › https://www.youtube.com/watch?v=iOO

vX0jmhJ4› https://www.youtube.com/watch?v=KFP

vdNbftOY

Solutions: a mixture of two or more substances that is uniform at the molecular level.

Solutions exist in every phase: solids, liquids, and gases.

Solid: A solution of two or more solids is an alloy.o Steel (a solution of Iron and Carbon)

Liquid: Liquid solutions may contain solids, liquids, and/or gases.o Salt Watero Soda

Gas: A solution of two or more gases.o Air (a solution of nitrogen, oxygen, argon,

carbon dioxide and traces of other gases

Solvent: the component of a solution that is present in the greatest amount.

Examples:o the water in soda is

the solvent.o The water in salt

water is the solvent.

Water dissolves sodium chloride (salt) to form a solution of sodium ions (Na+) and chlorine ions (Cl-)

Solute: any component of a solution other than the solvent.

Salt is the solute in a salt water solution.

What is one of the solutes in a soda?

When solute particles are evenly distributed throughout the solvent, the solute is dissolved

Dissolve: to separate and disperse a solid into individual molecules or ions in the presence of a solvent

Ionic compounds are solid “salts” with a crystalline structure

1. Polar solvent (H2O in this case) surrounds the solid crystal

2. NEGATIVE charges concentrated on the O of H2O bond to positive ion of the ionic compound

3. POSITIVE charges concentrated on the H’s of H2O bond to negative ion of the ionic compound

4. H 2O “tugs” apart the salt crystal ion by ion

o Cation (Na+): pulled by negative oxygen end

o Anion (Cl-): pulled by positive hydrogen end

5. Eventually all ions are surrounded by water molecules and are said to be in an AQUEOUS SOLUTION (THEY ARE DISSOLVED) the solid is “gone”

http://www.iun.edu/~cpanhd/C101webnotes/chemical%20reactions/images/sol.gif

Solubility: the amount of solute that can be dissolved in a specific volume of solvent under certain conditions.

Solubility is always given at a specific temperature since temperature strongly affects solubility.

Insoluble: a substance is insoluble in a particular solvent if it does not dissolve in that solvent.

o Oil is insoluble in water Saturated: a solution

is saturated if it contains as much solute as the solvent can dissolve.

Concentration: the ratio of solute to solvent in a solution.

Concentration =___mass of solute___ X

100%total mass of solution

Example:o A 10% sugar

solution contains 10g of sugar for every 90g of water

When a solute like sugar is mixed with a solvent like water, two processes are actually going on continuously.› Molecules of solute dissolve and go into

solution.› Molecules of solute come out of solution and

become “un-dissolved.” Equilibrium occurs when the rate of

dissolving equals the rate of coming out of solution. The solution has a maximum concentration of dissolved solute.

Supersaturated solution: there is more dissolved solute than the maximum solubility.

Solubility of gases in liquids increases with pressure.

Soda is fizzy because the CO2 2 was was dissolved in liquid at a high pressure.dissolved in liquid at a high pressure.

When you pop the tab on the soda can When you pop the tab on the soda can the pressure is released, causing the pressure is released, causing immediate supersaturation of the immediate supersaturation of the solution. solution.

Dissolved oxygen is essential to Dissolved oxygen is essential to underwater lifeunderwater life

Overall charge is neutral Charges are unequally distributed on

each side of the molecule H2O is a polar molecule

Water is a good solvent because of the way the H2O molecule is shaped.

A water molecule has a negative end (pole) and a positive end.

A molecule (like water) with a charge separation is called a polar molecule.

In general, like dissolves like: › water

dissolves polar substances

› non-polar solvents dissolve non-polar substances