sara abu-ghnaim a brief history of chemistry. section 1

SARA ABU-GHNAIM

A Brief History of Chemistry

Section 1

Bronze Casting

1) A worker is stoking the fire and two others are operating the bellows

2) Bronze ingots are melted by placing a ceramic melting-pot over the fire

3) The crucible with the molten metal is lifted off the fire with two poles

4) The liquid bronze is poured through funnels into the clay mould

Egyptian Blue Scarab

Egyptian Ceramic Vase

Philosopher’s Stone and an Arabic Alchemy Book

Fire Arrow

Antoine and Madame Lavoisier

Atomic Structure

Intermolecular Force

The Periodic Table

Potential Energy Model for a Chemical Reaction

Section 2

Mass Spectrometry

Is able to separate and measure atoms and compounds because moving charged species (ions) of different mass (and energy) are affected differently by magnetic or electric fields

Basically 3 steps: compounds or atoms are given charge (ions), accelerated, and a detector measures number of ions present

Properties and Importance of Commonly Recognized Isotopes- 2H,

14C, 60Co Isotope- form of an element whose nucleus contains a different number

of neutrons from an atom of that element, but has the same number of protons.

2H (deutrium) may become very important as a fuel for fusion power production since it combines in a fusion reaction with another isotope of hydrogen, tritium, to release large amounts of energy

14C is used in dating of materials containing carbon because when a living system dies, it ceases to maintain equilibrium with the 14C being produced by cosmic rays, so the amount of the isotope decreases at the half-life rate (5730 years). Thus, by measuring the amount of 14C left, archeologists can determine when the material ceased to be alive.

60Co does not occur in nature and has been used to kill cancerous tumor cells. Also kills harmful bacteria, so the isotope is used to sterilize foods for longer storage and medical equipment prior to use in surgery.

Isotope Notation

Wave and Particle Nature of the Electron and Photon

Mysterious to scientists- wavelike properties and particle properties could be exhibited simultaneously in experiments!!! WHAT! How is that possible!!

We believe that all matter can be represented by wave equations, but recognize that matter also exhibits properties typical of a particle

Quantum physics deals with this http://www.pbs.org/wgbh/nova/programs/ht/tm/3501.html?site=10&

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Electronegativity

Is the measure of one atom’s attraction of electrons from the adjacent atom to which it is chemically bonded

EN is a way to measure the winner in a “tug of war” for bonding electrons

If the EN values of the two atoms forming a bond are widely different, then the one with the higher value will win the electrons away from the other, forming an ionic bond.

With a smaller difference in the EN values, there would be a covalent bond (electron sharing).

If EN values are identical, there is a non-polar covalent bond.

The Importance of Hydrogen Bonding in Living Systems

The DNA molecule consists of chains of nucleic acids. Each of these contains the necessary ingredients for hydrogen bonding, namely: H atoms, O atoms, and N atoms.

Watson and Crick made a model that suggested that the hydrogen bonds between parts of DNA formed a double helix structure

There is hydrogen bonding between thymine, adenine, cytosine, and guanine

The Formation of Molecular Orbitals

When two or more atoms combine to form a chemical molecule, the electrons are arranged differently. The models that trace out the “electron waves” that constitute these electron positions are called molecular orbitals (MOs).

Sigma MO- overlap in which the new MO is concentrated along an imaginary line connecting the atoms

Pi MO- overlap where the electron wave shape is concentrated between the atoms, but away from the center line

F2- one sigma bond 02- one sigma and one pi bond N2- one sigma and two pi bonds Molecular orbitals are much more complex, so don’t worry

your little brains about it

The Resonance Concept Model

Resonance applies in some instances to bonding in molecules with more than 2 atoms

It was thought that bonds oscillated between two sides of the O3 molecule, but we now know that bonding is truly equivalent and it can best be thought of as 1.5 bonds on each side.

SO3 can be thought of similarly with 1 1/3 bonds on each side.

A very modern theory has come to replace to resonance model, so just know that it is WRONG

Decay Equations and Predicting Products of Decay

Unstable nuclei result in radioactive decay.Alpha decay results in the loss of two neutrons and

two protons from the parent nucleusBeta minus decay results in the loss of one neutron

and the gain of one proton from the parent nucleusPositron (or beta plus) decay results in the gain of one

neutron and the loss of one proton from the parent nucleus

Predictions of beta decay are based on the understanding that a nucleus is unstable because of an imbalance between the number of neutrons and the number of protons .

Alpha Bombardment Reactions

In these reactions, the mass stays the same, which conserves the number of protons and neutrons, which do not convert in alpha decay (they do convert in beta decay)

Fission and Fusion Reactions

Very simply, fission splits a massive element into fragments, releasing energy in the process. Fusion joins two light elements, forming a more massive element, and releasing energy in the process.

In fission of 235U, the products fly apart with a large amount of kinetic energy and this heat can be used to raise the temperature of water.

Fusion of 2H and 3H takes a lot of energy to overcome the positive charges and has not yet yielded enough energy to produce electrical power.

Section 3

Partial Pressures…

Dalton’s Law tells us that the total pressure is proportional to the number of particles of each gas

The value of the water pressure only depends on the temperature of the liquid. So you can just look this up in a table…

The Behavior of Gases under Extreme Conditions

There are 3 key assumptions with Kinetic Molecular theory (KMT)

However, most gases do not behave ideally in extreme conditions

Van der Waals developed a useful equation to monitor the behavior of non-ideal gases

Gases with large Van der Waals constants are good choices for refrigerator liquids

Carbon Dioxide

Liquid CO2 cannot be observed unless the pressure is at least 5.11 times the normal atmospheric pressure on Earth and at lower temperatures

Above the critical pressure point (point C on yall’s graphs), C02 becomes supercritical- acts as a liquid and gas, which is ideal for a solvent

When liquid CO2 is used, it is often recycled so it doesn’t hurt the environment

Raolt’s Law and Colligative Properties

Colligative properties are properties that depend on the amounts of substances present

Colligative property effects depend on the number of particle species present, not the moles of the original salt

Raolt established that the key factor determining the physical properties of a solution was the relative number of moles of solute in the solution

Reverse Osmosis vs. distillation of water

Section 4 (Last Section WHOOHO)

Acid-Base Reactions and Salts

When salt dissolves in water, its ions can interact with water molecules in a reaction called hydrolysis

Generally, the anions of weak acids will form basic salts

Cations of weak bases will form acidic saltsThere is no reaction when the cation of a

strong base and the anion of a strong acid join in water

Precipitates

The control of pH is important for plant growth

Perhaps the most well known contaminant is mercury (Figure 21)

Other precipitates are hazardous and can be inhaled, where they may stick to one’s lungs

Precipitation to remove toxic substances is a common process

Electroplating

Is the process of passing an electrical current through a solution containing a cation like Cu2+ and reducing it to Cu while coating an object with a thin layer of the metal

The amount of energy in electroplating is dependant on amount to be electroplated and number of electrons need to reduce a metal ion to its element

The electric charge on one mole of electrons was named the Faraday in honor of Michael Faraday

The Nernst Equation

Nernst equation connects cell potential to free energy changes for chemical reactions

One conclusion that can be drawn is that even if a cell has the same chemical in each compartment, if the concentrations are not equal, then there will be a cell voltage, even though E0=0. Such a cell is called a concentration cell.

Hess’s Law

This law states that the heat evolved or absorbed in a chemical process is the same whether the process takes place in one or in several steps

This is essentially a restatement of the law of conservation of energy!!!

This law allows us to calculate enthalpy changes that have not been measured based on our knowledge of other enthalpy changes that have been measured and using a cycle of reactions.

TIME FOR A HAPPIER SLIDESHOW!!!!

References

http://www.ehow.com/about_4728246_what-metal-casting-used.html http://www.reshafim.org.il/ad/egypt/trades/bronze_casting.htm http://www.signicast.com/casting_education/index.php http://en.wikipedia.org/wiki/File:Bronze_casting_by_the_Lost_Wax_Method.png http://weber.ucsd.edu/~dkjordan/arch/metallurgy.html http://en.wikipedia.org/wiki/Alchemy http://en.wikipedia.org/wiki/Glass http://en.wikipedia.org/wiki/Potter's_wheel http://en.wikipedia.org/wiki/Philosopher%27s_stone http://www.pyrouniverse.com/history.htm http://www.unomaha.edu/philosophy/NaturePhil.htm http://www.exampleessays.com/viewpaper/49419.html http://mattson.creighton.edu/History_Gas_Chemistry/Lavoisier.html http://www.biographybase.com/biography/Lavoisier_Antoine_Laurent.html http://www.cartage.org.lb/en/themes/Sciences/Chemistry/Generalchemistry/Energy/

LawofConservation/LawofConservation.htm http://www.grc.nasa.gov/WWW/K-12/airplane/thermo.html Science Research Guide