Chemistry

Why learn about chemistry in biology? All living things share the same chemical building blocks. All living things depend on chemical processes for survival.

Matter: ◦ Anything that takes up space and has mass. ◦ Example: rocks, wood, air, metal, paper, etc. Element: ◦ A pure substance that cannot be broken down into other substances. ◦ Example: gold, helium, mercury, oxygen

Elements continued… 25 essential elements (elements you can’t live without) 4 elements make up 96% of living matter- oxygen, hydrogen, carbon, and nitrogen. The other 4% is made up of mostly calcium, phosphorus, potassium, and sulfur. Trace elements: make up less than.01% of your body mass, but are essential to your health. ◦ Examples: iodine, iron, magnesium, copper, fluorine

Compound: ◦ A substance containing 2 or more elements that are chemically combined. ◦ Examples:  Water H 2 O  Oxygen O 2  Carbon Dioxide CO 2

Atoms Atom: smallest particle of an element ◦ Made of subatomic particles  Proton: single unit of positive charge  Electron: single unit of negative charge  Neutron: has no electric charge (neutral) ◦ Nucleus: central core of an atom, made of protons and neutrons. Therefore, the nucleus has a positive charge.

Atomic number: number of protons ◦ All atoms of the same element have the same number of protons, and therefore the same atomic number. ◦ No two elements have the same atomic number.

Periodic Table Label the families in your periodic table: ◦ Metals/ Nonmetals ◦ Noble Gases ◦ Halogens ◦ Alkali metals ◦ Alkaline Earth metals Fill in the table.

Isotopes ◦ same # protons, different # neutrons.

Radioactive isotope: nucleus decays over time, giving off radiation and energy.  Example: Carbon-14 ** Carbon-12 and Carbon-13 are very stable and will not change over time.

Energy Levels/Orbitals ◦ Electrons differ in the amount of energy they have ◦ Electrons differ in how tightly they are held by the t protons in the nucleus. ◦ Electrons fill the lowest energy level (closest to the nucleus) FIRST, then move to the higher energy levels, which are farther away from the nucleus.

Energy Levels/Orbitals ◦ First “energy level” or “oribtal” is closest to the nucleus.  Can hold up to 2 electrons  Example: Hydrogen ◦ Second energy  Holds up to 8 electrons  Example: Oxygen

Energy Levels/Orbitals A partially filled energy level makes an atom chemically reactive. ◦ This means they react with other atoms because they WANT to fill their outer energy level.

Chemical Bonding An attraction between 2 atoms that are transferring, receiving, OR sharing electrons. ◦ Ionic Bonds: transferring electrons  Example: NaCl ◦ Ions: atoms that become electrically charged (either positive or negative) **This happens by either losing or gaining an electron.

Chemical Bonding Covalent Bond: sharing electrons ◦ Examples: H2OH2O  CH 4 The number of bonds an atom can form usually equals the number of “extra” electrons in the outermost/ highest energy level.

Molecule: 2 or more atoms that are covalently bonded together form a molecule. Modeling Molecules: ◦ Chemical formula ◦ Structural formula ◦ Space model

Try drawing these.. C and H C and O H and O

Chemical Reactions Atoms are not created or erased in chemical reactions, they are just rearranged. Molecules are constantly being rearranged. Bonds are broken and new bonds are formed. When a bond is broken, energy is absorbed from the surroundings. When a bond is built, energy is released from the surroundings.

Chemical Reactions Chemical Equation ◦ Reactants: starting materials ◦ Products: ending materials

Water Polarity Hydrogen Bonding Adhesion and Cohesion Very Stable Special Density Universal Solvent

Electronegativity Oxygen is the most electronegative element. It pulls electrons closer to it’s orbital and therefore gives the atom a slightly negative charge and makes other atom slightly positive

Polarity Polar molecule: a molecule in which there is an internal separation of electric (electronegativity) charge. ◦ Example: Water **Water is NOT the only polar molecule!! (–) O HH (+)

Hydrogen bonding Hydrogen Bond: water molecules are held together by hydrogen bonds, due to the polarity of the molecule. This is a very weak bond because electrons are not being shared or transferred. (velcro)

Adhesion and Cohesion Cohesion: the tendency of molecules of the same kind to stick to each other. ◦ Ex: water sticks to water Adhesion: the tendency for molecules to be attracted to unlike molecules. ◦ Ex: water sticks to a glass

Water is very Stable Must gain or lose a lot of energy in order for the temperature to change! **This is why coastal areas have less extreme temperatures than inland areas.

Density: the amount of matter in a given volume. High density: tightly packed Low density: loosely packer In most substances, the solid state is more dense. In water, the solid state (ice) is less dense. ◦ Ice floats! Think: Why is this important for life?

Dissolving Solution: a uniform mixture of two or more substances Solvent: the substance that dissolves the other substance Solute: the substance being dissolved Aqueous solution: when water is the solvent

Acids and Bases In an aqueous solution, some molecules of water break apart into H+ ions and OH- ions. Other chemical compounds can contribute additional H+ ions as well.

Acids and Bases Acid: a compound that donates H+ ions to solutions. ◦ HCl (hydrochloric acid) breaks apart completely in an aqueous solution forming H+ ions and Cl- ions. ◦ on pH scale

Acids and Bases Base: a compound that removes H+ ions from a solution. ◦ NaOH (sodium hydroxide)does this by adding OH- to an aqueous solution, which bond with H+ ions in the solution, forming extra water molecules. ◦

Acids and Bases pH scale: describes how acidic or basic a solution is. The pH scale ranges from 0 (most acidic) to 14 (most basic).

Acids and Bases Each pH unit represents a change in the concentration of H+ ions tenfold. ◦ Ex: lemon juice at pH 2 has 10x more H+ ions than the same amount of grapefruit juice at pH 3. Pure water and aqueous solutions that have equal amounts of H+ and OH- ions are said to be neutral, with a pH of 7.

Acids and Bases Buffers: substances that cause fluids to resist changes in pH. ◦ Accepts H+ ions when the levels are too high. ◦ Donates H+ ions when the levels are too low.

Acidic solution Neutral solution Basic solution

Acidic solution pH scale Battery acid Lemon juice, gastric juice Grapefruit juice, soft drink, vinegar, beer Tomato juice Neutral solution Basic solution NEUTRAL [H + ]=OH – ] Increasingly ACIDIC (Higher concentration of H + ) Increasingly BASIC (Lower concentration of H + ) Rain water Human urine Saliva Pure water 6 7 Human blood, tears Seawater Milk of magnesia Household ammonia Household bleach Oven cleaner 14

Functional Groups Small characteristic groups of atoms that are frequently bonded to the carbon skeleton of organic groups. They have specific chemical and physical properties. They are usually chemically reactive. Depending on their number and arrangement, they determine unique chemical properties or organic molecules in which they occur.

Functional Groups Hydroxyl Group Carbonyl Group Carboxyl Group Amino Group Phosphate Group Methyl Group

Hydroxyl Group --OH It is polar because Oxygen draws the extra electrons from the rest of the molecule, making it slightly negative on that side. Makes the molecule it is attached to soluble Found in alcohols

Carbonyl Group --CO Also polar Makes the molecule water soluble Found in sugars Ex: aldehyde and ketone

Carboxyl Group --COOH (hydroxyl and carbonyl group) Also polar Makes the molecule water soluble Present in some amino acids (carboxyl acids) It is SO polar, that is dissociates as H+ (acid) sometimes.

Amino Group --NH 2 Also polar Makes the molecule water soluble Present in all amino acids Acts as a weak base because it can accept H+ ions

Phosphate Group H 3 PO 4 Polar Makes the molecule water soluble Used for energy storage Loss of 2 protons by dissociation will leave the molecule reactive Since is can lose protons, it has acidic properties

Methyl CH 3 Nonpolar Hydrophobic ****Properties come 2 nd to all other functional groups!