My Education Philosophy

I believe that science and technology are the backbone of the nation's strength. Science teachers are therefore some of the most critical people in guiding our nation into the future. I believe that teachers must have exceptional knowledge of their subject matter. students need to be "sold" on science, and a science teacher who does not love science subject to its core probably should not be teaching. I believe that science teachers must stay current with knowledge from within their field. Science subjects especially chemistry is an ever-changing discipline, and a teacher who does not up-to-date on recent developments in their field cannot be an effective teacher.

I believe that inquiry learning, when used properly, can produce question asking, critical thinking and problem solving skills required for the success in the twenty-first century. unfortunately,  in this era of content-based accountability in education, the body of knowledge required is so broad as to leave little time for inquiry-based lessons. However, I believe that at least 5% of the curriculum should be structured to be inquiry-based. This is a small sacrifice in time with a large potential payback in student performance and attitude.

I believe in “24/7 involvement.” Students should be thinking of science and math constantly. As a teacher, I am committed to making myself available to my students through e-mail and instant messaging, so that I can answer students’ questions at any time of day or night. I encourage discussion amongst classmates, so that they may synthesize physical thoughts on their own. Finally, I encourage my students to keep an eye on the natural phenomena around them, to build curiosity and to develop “physical intuition.”

I believe that science isn’t easy. Standards should be constructed in a way that all learners are challenged to an appropriate level for them. However, a difficult course needn’t have a difficult instructor. My philosophy is to create a framework of high expectations, while simultaneously offering support for students to meet those demands.

I believe that science courses should be taught in an interdisciplinary fashion. Too often, science is taught within the “silo model” — distinct categories of earth science, biology, chemistry, and physics — without anything to connect content from one field with that of another. In the twenty-first century, so-called “hyphenated sciences” are the norm (e.g., biochemistry, biophysics, chemical physics, nanotechnology, astrobiology). Teachers, even at the high-school level, must prepare their lectures with an eye toward connecting all disciplines within science. Teachers must work to break down the silos and convince students that science is one great field, not many smaller independent sub-fields.

Most of all, I believe that the most important trait science teachers can instill in their students is curiosity. Science is a process, not a body of knowledge. The most successful scientists ask more questions than they answer. I ask my students to ask questions about what they see, and encourage them to use their knowledge and physical intuition to develop physical explanations.

Finally, I believe that students work harder than ever in their academic and extracurricular activities. I have the utmost respect for students, and I try to demonstrate that respect in every interaction with students, parents, fellow teachers, and supervisors.

I believe in science, I believe in education, I believe in students, and I believe in the responsibility of humankind to control its own destiny through science and engineering. I wish to do my small part.

Distillation Process

Distillation is based on the fact that the vapour of a boiling mixture will be richer in the components that have lower boiling points.

Therefore, when this vapour is cooled and condensed, the condensate will contain more volatile components. At the same time, the original mixture will contain more of the less volatile material.

Distillation columns are designed to achieve this separation efficiently.

Although many people have a fair idea what “distillation” means, the important aspects that seem to be missed from the manufacturing point of view are that:

	distillation is the most common separation technique
	it consumes enormous amounts of energy, both in terms of cooling and heating requirements
	it can contribute to more than 50% of plant operating costs

The best way to reduce operating costs of existing units, is to improve their efficiency and operation via process optimisation and control. To achieve this improvement, a thorough understanding of distillation principles and how distillation systems are designed is essential.

voltaic cell

Voltaic Cells

A Voltaic Cell (also known as a Galvanic Cell) is an electrochemical cell that uses spontaneous redox reactions to generate electricity. It consists of two separate half-cells. A half-cell is composed of an electrode (a strip of metal, M) within a solution containing Mⁿ⁺ ions in which M is any arbitrary metal. The two half cells are linked together by a wire running from one electrode to the other. A salt bridge also connects to the half cells. The functions of these parts are discussed below. 

Half Cells

Half of the redox reaction occurs at each half cell. Therefore, we can say that in each half-cell a half-reaction is taking place. When the two halves are linked together with a wire and a salt bridge, an electrochemical cell is created.

Electrodes

An electrode is strip of metal on which the reaction takes place. In a voltaic cell, the oxidation and reduction of metals occurs at the electrodes. There are two electrodes in a voltaic cell, one in each half-cell. The cathode is where reduction takes place and oxidation takes place at the anode. The figures below illustrate a cathode and an anode.

Through electrochemistry, these reactions are reacting upon metal surfaces, or electrodes. An oxidation-reduction equilibrium is established between the metal and the substances in solution. When electrodes are immersed in a solution containing ions of the same metal, it is called a half-cell. Electrolytes are ions in solution, usually fluid, that conducts electricity through ionic conduction. Two possible interactions can occur between the metal atoms on the electrode and the ion solutions.

1. Metal ion Mⁿ⁺ from the solution may collide with the electrode, gaining "n" electrons from it, and convert to metal atoms. This means that the ions are reduced.
2. Metal atom on the surface may lose "n" electrons to the electrode and enter the solution as the ion Mⁿ⁺ meaning that the metal atoms are oxidized.

When an electrode is oxidized in a solution, it is called an anode and when an electrode is reduced in solution. it is called a cathode.

Anode

The anode is where the oxidation reaction takes place. In other words, this is where the metal loses electrons. In the reaction above, the anode is the Ag(s) since it increases in oxidation state from 0 to +1.

Cathode

The cathode is where the reduction reaction takes place. This is where the metal electrode gains electrons. Referring back to the equation above, the cathode is the Cu(s) as it decreases in oxidation state from +2 to 0. 

Remembering Oxidation and Reduction

When it comes to redox reactions, it is important to understand what it means for a metal to be “oxidized” or “reduced”. An easy way to do this is to remember the phrase “OIL RIG”.

OIL = Oxidization is Loss (of e^-)

RIG = Reduction is Gain (of e^-)

In the case of the example above Ag⁺(aq) gains an electron meaning it is reduced. Cu(s) loses two electrons thus it is oxidized.

Salt Bridge

The salt bridge is a vital component of any voltaic cell. It is a tube filled with an electrolyte solution such as KNO_3(s) or KCl_(s). The purpose of the salt bridge is to keep the solutions electrically neutral and allow the free flow of ions from one cell to another. Without the salt bridge, positive and negative charges will build up around the electrodes causing the reaction to stop.

Flow of Electrons

Electrons always flow from the anode to the cathode or from the oxidation half cell to the reduction half cell. In terms of E^ocell of the half reactions, the electrons will flow from the more negative half reaction to the more positive half reaction.

Cell Diagram

A cell diagram is a representation of an electrochemical cell. The figure below illustrates a cell diagram for the voltaic shown in Figure 1 above.

Figure 2 Cell Diagram

When drawing a cell diagram, we follow the following conventions. The anode is always placed on the left side, and the cathode is placed on the right side. The salt bridge is represented by double vertical lines (||).  The difference in the phase of an element is represented by a single vertical line (|), while changes in oxidation states are represented by commas (,).

Constructing a Cell Diagram

When asked to construct a cell diagram follow these simple instructions.
Consider the following reaction:

2Ag⁺_(aq) + Cu_(s) ↔ Cu²⁺_(aq) + 2Ag_(s)

Step 1: Write the two half-reactions.

Ag⁺(aq) + e^- ↔ Ag_(s)

Cu_(s) ↔ Cu²⁺_(aq) + 2e^-

Step 2: Determine the cathode and anode.

Anode: Cu_(s) ↔ Cu²⁺_(aq) + 2e-     

Cathode: Ag⁺(aq) + e^- ↔ Ag(s)

Cu_(s) is losing electrons thus being oxidized. Oxidation happens at the anode. Ag⁺ is gaining electrons thus is being reduced. Reduction happens at the cathode.
Step 3: Construct the Diagram.

Cu_(s) | Cu²⁺_(aq) || Ag⁺_(aq) | Ag(s)

The anode always goes on the left and cathode on the right. Separate changes in phase by | and indicate the the salt bridge with ||.

Cell Voltage/Cell Potential

The readings from the voltmeter give the reaction's cell voltage or potential difference between it's two two half-cells. Cell voltage is also known as cell potential or electromotive force (emf) and it is shown as the symbol E_cell. 

Standard Cell Potential: E^o_cell = E^o_{right(cathode)} - E^o_left(anode)

The E^o values are tabulated with all solutes at 1 M and all gases at 1 atm. These values are called standard reduction potentials. Each half-reaction has a different reduction potential, the difference of two reduction potentials gives the voltage of the electrochemical cell. If E^ocell is positive the reaction is spontaneous and it is a voltaic cell. If the E^ocell is negative, the reaction is non-spontaneous and it is referred to as an electrolytic cell.

This is a link that shows the standard reduction potentials of all common half-reactions: http://butane.chem.uiuc.edu/cyerkes/.../standpot.html

Practice Problems

Consider the following two reactions:

a) Cu_²⁺(aq) + Ba_(s) --> Cu_(s) + Ba²⁺_(aq)

b) Al_(s) + Sn²⁺_(aq) --> Al³⁺_(aq) + Sn_(s)

1. Split the reaction into half reactions and determine their E^o value. Indicate which would be the anode and cathode.

2. Construct a cell diagram for the following each reactions.

3. Determine the E^o_cell for the voltaic cell formed by each reaction.

*Solution are given below.

Solutions

1.a)    Ba²⁺_(aq) + 2e- --> Ba_(s)     E^o = -2.92 V        Anode

  Cu_²⁺(aq) + 2e- --> Cu_(s)     E^o = +0.340 V     Cathode

1.b)    Al³⁺_(aq) 3e^- --> Al_(s)           E^o = -1.66 V        Anode

          Sn²⁺_(aq) --> Sn_(s) +2e^-      E^o = -0.137 V     Cathode

2.a)    Ba²⁺_(aq) | Ba_(s) || Cu_(s) | Cu_²⁺(aq)

2.b)    Al_(s) | Al³⁺_(aq) || Sn²⁺_(aq) | Sn_(s)

3.a)    E^o_cell = 0.34 - (-2.92) = 3.26 V

3.b)    E^o_cell = -0.137 - (-1.66) = 1.523 V

What happen when mix bromine with alcohol

Substitution, Addition and Elimination Reactions

Introduction:

Substitution, addition, and elimination reactions are of great importance in a major branch of chemistry known as Organic Chemistry, which covers the chemistry of compounds of carbon. These reactions, which generally involve covalently bonded molecules, are also found, to a much more limited extent with other compounds.

Substitution reactions:

A substitution reaction is a reaction in which an atom (or group of atoms) in a molecule is replaced by another atom or group of atoms:

Example 1:

The gas ethane, CH₃CH₃ reacts with bromine vapour in the presence of light to form bromoethane, CH₃CH₂Br and hydrogen bromide, HBr. In the process, a hydrogen atom in ethane has been substituted for a bromine atom:

Example 2:

Ethanol, CH₃CH₂OH, reacts with hydrogen iodide, HI, to form iodoethane and water. Here, a group of atoms, OH, has been replaced by an iodine atom:

Example 3:

Benzene, C₆H₆, reacts with bromine in the (presence of iron bromide as catalyst) to form bromobenzene, C₆H₅Br. This results in a hydrogen atom being replaced by a bromine atom:

Addition reactions:

An addition reaction is a reaction whereby a molecule reacts with another molecule having one or more multiple covalent bonds so as to form a molecule whose molecular mass is the sum of the molecular masses of the reacting molecules:

Example 3:

Ethene, CH₂=CH₂ has a double bond joining the two carbon atoms. This substance can add a hydrogen molecule (in the presence of platinum as catalyst) to form ethane, CH₃CH₃:

Example 5:

Ethyne, C₂H₂ has a triple bond joining the two carbon atoms. Hydrogen bromide adds onto this triple bond to form 1,1-dibromoethane, CH₃CHBr₂:

Elimination reactions:

An elimination reaction is a reaction whereby a multiple covalent bond is formed in a molecule by the removal of another, usually smaller molecule:

Example 6:

Ethanol, CH₃CH₂OH, when treated with concentrated sulphuric acid, H₂SO₄, loses 2 hydrogen atoms and one oxygen atom, forming ethene, CH₂=CH₂ and water (the atoms that have been eliminated are shown in red):

When an elimination reaction removes the elements of water from a compound, as in the reaction above, the reaction is called a DEHYDRATION REACTION.

Example 7:

Bromoethene, CH₂=CHBr, when treated with potassium hydroxide dissolved in ethanol, loses one hydrogen atom and one bromine atom, forming ethyne, CH≡CH (the atoms that have been eliminated are shown in red):

When an elimination reaction removes the elements of a halogen acid (HCl, HBr, HI) from a compound, as in the reaction above, the reaction is called a DEHYDROHALOGENATION REACTION.

Formation of ionic bond

Cleansing action of soap.......