Water and Solutions

Chemistry Basics : MATTER: anything that has mass and occupies space ELEMENTS (in Periodic Table): make up matter. ATOMS: make up elements. made of protons, neutrons, and electrons. protons are positive, electrons are negative and neutrons have no charge ION: A charged particle. Ex.: Na + and Cl- (separated NaCl: salt) (If the no. of protons and electrons in the atom of an element are NOT the same)

Water molecule chemical formula: H2O Is POLAR: Different charges in opposite sides of the molecule. Hydrogen atoms H (+) Oxygen atom O (-)

Hydrogen Bonds hold water molecules together 5. the negative charge on the Oxygen atom attracts the positive charge on the Hydrogen atom (HYDROGEN BOND)

It is because of Waters’ Polarity and Hydrogen Bonding that water is able to do Extraordinary things!!

Properties of water Properties Adhesion Cohesion Less dense when frozen Universal Solvent High heat of vaporization High specific heat Homeostasis

ADHESION Water molecules make hydrogen bonds with different surfaces/substances Example: Capillary action, as in water moving up a plant stem, transpiration

Adhesion Causes water to… Form spheres & hold onto plant leaves Attach to a spider web

COHESION Water molecules stick together Results in Surface Tension and produces a Surface Film surface tension = measure of strength of water at surface

LESS DENSE AS SOLID Liquid water molecules are unstable: hydrogen bonds are constantly breaking and reforming. Frozen water molecules are stable: hydrogen bonds are “locked” into a crystal

Water is Less Dense as a Solid Which is ice and which is water? 1

Why ice really does float: Air

***Solvents dissolve solutes creating solutions! *** Universal solvent Solvent = a substance in which another substance is dissolved in Solute = a substance dissolved in a solvent Solution = when a solvent and solute are combined ***Solvents dissolve solutes creating solutions! ***

Solution Ionic compounds disperse as ions in water (Salt = Na+ and Cl-) Water molecules then attach to the ions dissolved in the solution.

polar: it has slightly charged regions. hydrophilic: Attracted to water Ex.: water nonpolar: it does not have charged regions, hydrophobic: not attracted to water. Ex.: oil POLAR DISSOLVES POLAR! Water is polar so it dissolves all polar molecules (example salt, sugar) NONPOLAR DISSOLVES NONPOLAR! Water will not dissolve non-polar molecules (example Oil, grease)

High Heat of vaporization Amount of energy to convert 1g of a substance from a liquid to a gas As water evaporates, it removes a lot of heat with it (cooling effect).

High Specific Heat Amount of heat needed to raise or lower 1g of a substance 1° C. Water resists temperature change

Homeostasis Organism’s ability to maintain stable internal conditions despite changing conditions. Water is important to this process because: a. It’s a good insulator b. Resists temperature change c. Universal solvent d. Coolant e. Ice protects against temperature extremes (insulates frozen lakes)

pH scales measures ACIDs OR BASEs The scale goes from values 0 through 14.

Acids Bases pH between 0 and 6.9 on the pH scale Taste sour Corrode metals (acid rain) Release lots of hydronium ions (H+) Ex.: lemon juice, vinegar, coke, coffee Bases pH between 7.1 and 14 on the pH scale Taste bitter, chalky Feel soapy, slippery Release lots of hydroxide ions (OH-) Ex.: soaps, detergents, cleaners

ACID BASE H+ = hydronium ion OH- = hydroxide ion

Buffer Neutral pH number is 7 Examples: blood, water Solutions that keep the pH within a particular pH range. Buffered aspirin has a coting on it to Keep the acid in your stomach from dissolving it right away.