A. Definitions Solution - homogeneous mixture Solute - substance being dissolved Solvent - present in greater amount. The substance doing the dissolving

Solutions Soluble – Something that can be dissolved into solution Ex. Salt is soluble in water Insoluble – Something that cannot be dissolved Ex. Oil is insoluble in water “magic sand” is insoluble in water.

Water as a Universal Solvent Because water dissolves SO MANY COMPOUNDS and MOLECULES, Water is usually referred to as the UNIVERSAL SOLVENT.

water

Water Molecule The water molecules is made up of one oxygen atom and 2 hydrogen atoms, covalently bonded into a V-shaped molecule. (the water is bent

Structure of Water Oxygen is more electronegative than hydrogen (it has a stronger attraction for the shared electrons). This causes an uneven distribution of charge within each covalent bond since electrons spend more time near O than H. The bond is said to be polar.

A polar bond results from the unequal sharing of electrons between atoms in a molecule.

Polarity of water Polarity of H2O molecule results in attraction of H2O molecules to each other. partial "+“charge of the H atoms attracted to partial "-" charge of the O atoms in another H2O molecule

Like dissolves like Since water is a polar molecule it dissolves other polar molecules AND ionic compounds

Non-polar molecules such as oil, and gasoline do not dissolve in water

But what does dissolving means?

Solvation occurs at the surface of the solute solvent particles surround solute particles (+/- attraction) solute particles are pulled into solution

Like Dissolves Like NONPOLAR POLAR

Guided Practice Lets see how much we have learned today!!!!! (See solution Chem practice questions)

FACTORS THAT AFFECT THE RATE OF DISSOLVING!!!

Rate of Solution Solids dissolve faster... more stirring small particle size (increased surface area) high temperature

Gases dissolve faster... no shaking or stirring high pressure low temperature

Concentration Concentrated solution large amount of solute Dilute solution small amount of solute

A. Concentration UNSATURATED SOLUTION more solute dissolves no more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form concentration

B. Solubility Solubility maximum grams of solute that will dissolve in 100 g of solvent at a given temperature varies with temperature based on a saturated solution

B. Solubility Solubility Curve shows the dependence of solubility on temperature

B. Solubility Solids are more soluble at... high temperatures. Gases are more soluble at... low temperatures. high pressures (Henry’s Law).

B. Electrolytes Electrolyte Weak Electrolyte Non- Electrolyte + salt - + acetic acid - + sugar Electrolyte Weak Electrolyte Non- Electrolyte solute exists as ions only solute exists as ions and molecules solute exists as molecules only

B. Electrolytes Dissociation separation of +/- ions when an ionic compound dissolves in water

B. Electrolytes Ionization breaking apart of polar covalent molecules into ions when dissolving in water

C. Colligative Properties properties of solutions that depend only on solute concentration Freezing Point Depression solutes lower the f.p. of a solvent Boiling Point Elevation solutes raise the b.p. of a solvent

C. Colligative Properties Effect increases as the solute concentration increases. Uses: antifreeze making ice cream salting icy roads

Mixtures that are not Solutions Suspensions – A temporary mixture in which the particle eventually settle Colloid- A mixture that has large particles like milk, egg whites, mayonnaise. These often look homogeneous or the same throughout You can tell a colloid by the Tyndall Effect or the scattering of light it exhibits