Chapter 2Chemistry

Unit 4Lecture 1

Topic: Introduction to Chemistry

Covers Chapter 2 (pg 30 – 32)

Recap:Living vs. Nonliving

DifferencesLiving Organisms:

Made up of at least one cell * Has a metabolismHas DNA  * Maintains homeostasisNeeds a food source  * Responds to stimuliGrows * Reproduce

Similarities:All things (living and nonliving) are made up of

MATTERMATTER - anything that takes up space and has massMASS - how much matter an object has

Atoms

Matter is made up of chemical elements, or ATOMSATOM - basic building block of matter

Smallest, stable unit of matterAn element is a specific type of atom

Elements/atoms cannot be broken down into a simpler  stable type of matter

All known elements are arranged into a tablePERIODIC TABLE OF ELEMENTS

Over 100 known elements on Periodic Table, but only around 30 are  important to living organisms4 Major elements in living organisms:

~ Oxygen  ~Hydrogen ~ Carbon ~Nitrogen

Atoms

Atoms (elements) are made up of three basic parts:

1. PROTONS  2. NEUTRONS  3. ELECTRONS

Protons Neutrons Electrons

Charge Positive Neutral Negative

Mass Large Large Very Small

Atoms

Atomic Mass = Number of Protons + Number of Neutrons

Atomic charge = Number of Protons + Number of electrons

Neutral atoms (atom without a + or – charge) have the same number of electrons as protons

Protons and Neutrons are located in the center of the atom, known as the NUCLEUSElectrons circle around the nucleus in orbitals

1st level can hold 2 electrons 2nd level can hold 8 electrons

Element stable when outer orbital (energy level) is fullThe only elements that have a full outer orbital

are found in the last column of the periodic tableThese elements are known as inert gas or

noble gas

End of Lecture 1

Unit 4Lecture 2

Topic: Types of Bonds

Covers Chapter 2 (pg 33 – 34)

Types of Bonds

Most elements are not stable as an individual atom

Elements that are unstable (do not have a full outer orbital) will CHEMICALLY combine with other elements to form a molecule.

When elements chemically combine, it is called a bond

Types of Bonds

Types of Bonds:Covalent Bond – two atoms sharing electrons

Very strong in a watery solutionExample: Carbon dioxide, Oxygen Gas, Water

Types of Bonds

Types of Bonds:Ionic Bond – bond between a positively charged

ion and a negatively charged ion (opposites attract)

Ion – an atom with a positive or negative charge

Ionic bond easy to break in a watery solutionWhen the ionic bond breaks, will go back to

a positively charged ion and a negatively charged ion

Types of Bonds Hydrogen Bond

Type of ionic bond that forms between two different water molecules

Very weak, broken easily

But, Hydrogen bonds are very important to living organismsCauses Cohesion and Adhesion to occur

Types of Bonds Hydrogen Bond

Cohesion – attractive forces between water moleculesEXAMPLE: Surface Tension, Rain Drops

Adhesion – attractive forces between water molecules and another compound/surfaceAllows water to move up through narrow

tubes against gravity (clings to sides of tubes)

EXAMPLE: Helps plants transport water from roots to leaves

End of Lecture 2

Unit 4Lecture 3

Topic: Water, pH, Chemical Reactions

Covers Chapter 2 (pg 35 – 42)

Solutions

Solution – mixture of 2 or more substances

Solute – substance dissolved

Solvent – the material dissolving the solute Aqueous Solution – solution in which water is

the solvent

Concentration – measurement of the amount of solute dissolved in the solvent

Solutions – Water Water (H2O) is the universal solvent

Water is formed by covalent bonds between Hydrogen and OxygenPolar Molecule – electrons not shared evenly,

resulting in a molecule with one side having a negative charge & the other side having a positive charge

The negative charge and positive charge cancel each other out, so the molecule

(as a whole) is considered neutral (no charge)

In water, Oxygen has a stronger pull on the electronsThis makes Oxygen slightly negative and

the Hydrogens slightly positive  

pH Scale

Measuring the concentration of Hydronium Ions (H+) and Hydroxide Ions (OH-)

Scale from 0 – 14

pH Scale Neutral solution

pH = 7; OH = HExample: water (7), cells (6.5 - 7.5)

AcidpH < 7; OH– < H+More H+ (hydronium) ions than OH– (hydroxide)

ionsSour taste, Highly corrosiveExample: vinegar (3), stomach acid (2), acid rain

(<5.6)

Base (aka "Alkaline”)pH > 7; OH– > H+More OH– (hydroxide) ions than H+ (hydronium)

ionsBitter taste, Slippery feel, SoapExs: Milk of Magnesia (10.5), Ammonia (11.5), Soap

pH Scale

Units on the pH scale are logarithmicIncrease or decrease by factors of 10Example: pH 3 is not two times more acidic

than a pH 6, but 1,000 times more acidic!

BuffersNeutralize small amounts of an acid or baseBuffering systems help keep our body’s

fluids stay at a normal and safe pH level

Energy

Energy – ability to do work or cause changeComes in many forms, and can change formsSome types of energy:

Potential, Kinetic, Chemical, Thermal, Solar, Nuclear

Free Energy – energy in a system that is available  for work (to fuel cell processes)

Activation Energy – energy required to start a chemical reaction

Catalyst – chemical that reduces amount of activation energyEnzymes are a main type of catalyst

Activation Energy

Energy

Na + Cl NaCl

 Reactants  Product(s) Arrow always points to products

Exergonic Reaction – releases free energy

Endergonic Reaction – absorbs free energy

Energy

Life processes require a constant supply of energyMost common type of cell energy is ATP

(Adenosine Triphosphate)Made up of a 5-carbon sugar, adenine

molecule, and a chain of THREE phosphate groups

The phosphate molecules are held together by covalent bonds

When the last phosphate's bond is broken, a lot of energy is released. The energy is used to fuel cell reactionsForms ADP (Adenosine Diphosphate)

End of Lecture 3