Solution Chemistry

Solutions A mixture in which the molecules are equally distributed (homogeneous) Properties 2 parts: solute - substance dissolved solvent - dissolving medium particles are small atoms, ions, or molecules Can be separated by physical means May or may not conduct electricity Most common solvent is water (universal solvent) Solutions with water as solvent are aqueous solutions Tinctures have alcohol as the solvent

Solutions and Conductivity Electrolytes are substances whose water solutions conduct electricity well due to presence of ions - strong acids and strong bases Nonelectrolytes do not conduct electricity well - sugar, water, alcohol, weak acids and weak bases

Solubility The measure of how much of a solute can be dissolved in a given amount of solvent Rate of solubility can be increased by increasing temperature (solid in liquid) decreasing temperature (gas in liquid) increase pressure (gas in liquid only) movement increasing surface area of solute

Solution Concentration The amount of solute dissolved in a certain amount of solvent concentrated - a lot of solute dilute - little solute Saturated - solution that contains all the solute it possibly can at a given temperature Unsaturated - solution that can contain more solute at a given temperature Supersaturated - holding more solute than normally possible at that temperature

Special properties A solute dissolved in a liquid solvent lowers the freezing point Also raises the boiling point

Diffusion – movement of particles from an area of high concentration to an area of lower concentration Osmosis – special type of diffusion, movement of water across a membrane from an area of higher concentration of WATER to an area of lower concentration of water

Isotonic solution – solution has an equal osmotic pressure Hypertonic solution – solution with a greater concentration than the inside of a cell, will cause cell to shrink Hypotonic solution – solution with a lesser concentration than the inside of a cell, will cause cell to swell and sometimes rupture, in a plant cell increases turgor pressure Demo - http://www2.nl.edu/jste/osmosis.htm

ACIDS AND BASES

Acids Taste sour Turn litmus paper from blue to red Makes phenolphthalein colorless Usually contain hydrogen React with active metals to form hydrogen gas and a metal compound Proton donors – contain more hydronium ions (H30+) pH below 7

Bases Taste bitter Slippery to the touch Can be corrosive and poisonous Turn litmus paper from red to blue Turn phenolphthalein bright pink Emulsify (dissolve) fats and oils Proton acceptor- contain more hydroxide ions (OH-) pH above 7

pH Measure of the hydronium ion (H30+) concentration indicates how acidic a solution is - hydronium ion is formed by the attraction between a hydrongen ion and water 7 is neutral below 7- acid : above 7 - base indicators include litmus paper, phenolphthalein, pH paper, methyl orange, bromthymol blue, red cabbage juice, grape juice, blackberry jam and tea

Acid/Base Reactions Reaction is called neutralization The products of an acid/base reaction are salt and water Many salts created by these reactions are insoluble in water and crystallize - these fall out of the solution and are called precipitates a neutralization reaction is a double replacement reaction