chapter 2 chemistry. unit 4 lecture 1 topic: introduction to chemistry covers chapter 2 (pg 30 –...
TRANSCRIPT
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