Basics of Chemistry

Basics of Chemistry

BASICS OF CHEMISTRY Biology 9/22/14 ALL THINGS ARE MADE OF ATOMS Parts of an atom: Part Locatio Electric n Charge

Mass Proton Nucleus Positive 1 mass unit Neutron

Nucleus None 1 mass unit Electron Orbiting in various energy levels

Negative Nearly zero The number of protons determines which element the atom is. When electrons vary it is an ion. When neutrons vary it is an isotope.

ATOMS BOND TOGETHER TO FORM LARGER MOLECULES 1. Covalent bonds= when atoms share electrons Depending on how many electrons are shared, can be either: Single or Triple Double

2. Ionic Bonds= when an electron from one atom is transferred to another atom. This leaves one positively charged ion and one negatively charged ion that are bonded to each other (opposites attract) Ionic molecules dissociate in water. Meaning the ions separate from one another and form a solution with the water. This solution will conduct electricity. 3. Hydrogen Bonds= When two molecules that have weak partial positive and weak partial negative parts (polar molecules) are attracted in a relatively weak interaction (think magnets)

TECHNICALLY NOT A BOND. Merely an attraction BOND STRENGTH: Bond Type Ionic Bond Strength Strongest (double and triple bonds are even stronger)

Strong Hydrogen Bonds Weakest Covalent Bond strength is determined by how much energy (heat) it takes to break

the molecule apart PROPERTIES OF WATER Biology 9/26/14 PROPERTIES OF WATER Water is POLAR!! POLAR covalent bond = unequal sharing of electrons Creates slightly positively charged and negatively charged sides of the molecule (like a magnet) Oxygen is an electron hog so the

oxygen is more (-) and hydrogens more (+) Hydrogen Bondattraction between water molecules Polarity and Hydrogen bonds give H2O some unique and very important properties! : 1. Cohesion, Adhesion and Surface Tension

cohesion = H2O attracted to other H2O molecules adhesion = H2O attracted to other materials surface tension = molecules at the surface are These are all created attracted to each other even because of the hydrogen bonding between molecules! more strongly because no like molecules

on one side 2. Capillary Action Because water has both adhesive and cohesive properties, it will climb up a narrow tube. Ex: Think water in a straw Ex: Water moves through trees this way 3. High Heat Capacity

It takes much more energy to heat H2O than most other liquids. Water also holds heat longer! Waters ability to store heat is HUGELY important for our climate!!! 4.Density Water is LESS dense as a solid! Because the hydrogen bonds are stable in ice each molecule of water is bound to four neighbors therefore spaced farther apart. This is also HUGELY IMPORTANT! If ice was at the

bottom a lake would continue to freeze until solid. (Poor fishies ) ACIDS AND BASES Biology 10/2/14 Acids Give up a Hydrogen ion (H+) when in water Taste sour Strong acids can burn skin & eyes Strong acids can dissolve metals Examples:

Lemon juice Vinegar Car battery acid Bases Produce a Hydroxide ion (OH-) when put in water Can taste bitter Strong bases can burn skin & eyes Bases react more easily with protein than with metal; they are often used for cleaning Examples:

Milk Baking soda Soap Drain cleaner (dangerous!) Chemicals that produce neither (H+) nor (OH-) ions are said to be neutral. Water is neutral because it would split into both ions equally. pH scale measures how acidic or basic a solution is. 0--------------7---------------14 Acid

Neutral Base The pH Scale p stands for potential and H stands for Hydrogen -the potential of a substance to produce Hydrogen ions pH scale ranges from 0 -14

pH 7 is neutral; neither acid nor base Low pH (0-6.9) = acid High pH (7.1-14) = base The closer to the ends of the scale, the stronger the solution BUFFERS Keep pH steady within a small range. Natural buffers are VERY important in Biology! (think about soil, lakes and streams, and oceans)

NEUTRALIZATION - Acid + Base= Water + a salt Example: HCl + NaOH = H2O + NaCl

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