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 H2O

Oxygen O2

Carbon Dioxide CO2

AtomsAtom: 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 BondingAn 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 BondingCovalent Bond: sharing electrons

◦Examples: H2O

CH4

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 ReactionsAtoms 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 ReactionsChemical Equation

◦Reactants: starting materials◦Products: ending materials

WaterPolarityHydrogen BondingAdhesion and CohesionVery StableSpecial Density Universal Solvent

ElectronegativityOxygen 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

PolarityPolar 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 CohesionCohesion: 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 StableMust 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 packedLow density: loosely packerIn 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?

DissolvingSolution: 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 BasesIn 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 BasesAcid: a compound that

donates H+ ions to solutions.◦HCl (hydrochloric acid)

breaks apart completely in an aqueous solution forming H+ ions and Cl- ions.

◦0-6.9 on pH scale

Acids and BasesBase: 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.

◦7.1-14

Acids and BasespH scale:

describes how acidic or basic a solution is.

The pH scale ranges from 0 (most acidic) to 14 (most basic).

Acids and BasesEach 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 BasesBuffers:

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

1

2

3

4

5

Lemon juice, gastric juice

Grapefruit juice, soft drink,vinegar, beer

Tomato juice

Neutral solution

Basic solution

NEUTRAL[H+]=OH–]

Incre

asin

gly

AC

IDIC

(Hig

her

con

cen

trati

on

of

H+)

Incre

asin

gly

BA

SIC

(Low

er

con

cen

trati

on

of

H+)

Rain water

Human urine

Saliva

Pure water

6

7

Human blood,tears

Seawater

8

9

10

11

12

13

Milk of magnesia

Household ammonia

Household bleach

Oven cleaner

14

Functional GroupsSmall 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 GroupsHydroxyl GroupCarbonyl GroupCarboxyl GroupAmino GroupPhosphate GroupMethyl 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--NH2

Also polar

Makes the molecule water soluble

Present in all amino acids

Acts as a weak base because it can accept H+ ions

Phosphate GroupH3PO4

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

MethylCH3

Nonpolar

Hydrophobic

****Properties come 2nd to all other functional groups!