In turn, both kinds of spectra can be of continued development of On-line development, or development clustered in lines (bands).

The spectra observed during the lessons are for spectra emission lines and continuous absorption spectra.

The emission spectra lines reveal the nature of the element. Andalusia vaporize it and expose it to the flame, the atoms of the element are excited, and then desexcitán dose broadcasts in the form of photon energy that was delivered. This corresponds to a power line specific wavelength characteristic of the element.

Continuous absorption spectra are obtained with light to illuminate some white colored transparent material, with the disappearance of vast regions of the visible spectrum. This is because to pass the light through the atoms of the material they responded vibrating and absorbing the light of equal frequency.

Molecular absorption spectroscopy: Spectrophotometer

All molecular species have a limited number of levels discrete energy: the energy level is the lowest state fundamental. When a photon of radiation passes close to a molecule is likely to occur if and only if absorbing the energy of photon exactly matches the energy difference between the fundamental state of the molecule and one of its states with a level Higher energy. After a very short time the excited species relaxes to its original state, giving its excess energy to other atoms or molecules of the medium.

Spectrophotometry: Spectral scans

The Lambert-Beer law governing the molecular absorption, and it represents by the equation l = Abs. c. a; where is absorbance Abs of the sample, l is the thickness of it, his concentration and c absorbed, constant feature of the species and the length of wave.

It spectrophotometer measures the intensity of the light transmitted through a container that contains the sample, and through this information can knowing the absorbency of the sample to a given wavelength. In we use our experience to do the spectrophotometer spectral scanning of two substances and the corresponding mixture of the same.

Beer's law also applies to solutions containing more than one kind of absorbing substance. Assuming that there is no interaction between different species, the total extinction for a system with many components is the sum of the individual absorbency. The spectral scanning of the mixture will be the average of sweeps spectrum of its individual components, and will be below them, and that by mixing the ingredients is diluted the solution, and concentration is lower. The scans obtained with spectral The spectrophotometer reveal the color of the sample, as the same absorbs its complementary color of the radiation that reaches and white variation of the absorbency with the merger will occur in the region the complementary color, in contrast, absorbencies will be amended very with little radiation from the color of the sample.

CEC: Canadian Electrical Code
ULC: Underwriters’ Laboratories of Canada
NEMA: National Electrical Manufacturers Association
CEA: Canadian Electricity Association
ANSI: American National Standards Institute
IEEE: Institute of Electrical and Electronics Engineers
CSA: Canadian Standards Association
NRCC: National Research Council Canada
NFPA: National Fire Protection Association
OBC: Ontario Building Code
ISO: International Organization for Standardization

Part 2: Wires and Cables

AWG: American Wire Gauge
kcmil: Kilo Circular Mils
NMSC: Non-Metallic Sheathed Cable
NMD90: Non-Metallic Dry Sheathed Cable 90°C
NMW: Non-Metallic Wet Sheathed Cable
NMWU: Non-Metallic Wet Underground Sheathed Cable
AC-90: Armored Cable 90°C
ACWU: Armored Cable Wet Underground
MIC: Mineral Insulated Cable
LWMI: Light Weight Mineral Insulated
ASC: Armor-Sheathed Cable
NS-1: Neutral Supported Cable
NSF-2: Neutral Supported Flame Cable
FCC: Flat Conductor Cable
CFC: Communication Flat Cable
USEI90: Underground Service Entrance Cable
XLPE: Cross-Linked Polyethylene
TW75: Thermal Plastic Insulated Wet
RA90: Rubber Aluminum Sheathed
FAS: Fire Alarm and Signal Cable
LVT: Low Voltage Thermal Plastic
ELC: Electronic Load Controller
TEW: Thermal Plastic Insulated Electrical Wire
SEW-2: Silicon Rubber Insulated Wire
ZSW: Station Wire
ASLC: Airport Series Lighting Cable
TC: Tray Cable
CIC: Control and Instrumentation Cable
ICS: Ignition Cable Silicon

Part 3: Conduits, Raceways and Miscellaneous

GRS: Galvanized Rigid Steel Conduit
HFT: Halogen-Free Thermal Plastic
ENMT: Electrical Non-Metallic Tubing
PVC: Polyvinyl Chloride
RTRC: Rigid Non-Metallic Conduit of Reinforced Thermal-Set Material
EMT: Electrical Metallic Tubing
DC: Direct Current
DP: Drip Proof (Code Book 2-404 A)
WP: Water Proof (Code Book 2-404 B)
TE: Totally Enclosed
HRC: High Ruptured Capacity (Fuses)
GFCI: Ground Fault Circuit Interrupter
AFCI: Arc Fault Circuit Interrupter
CATV: Community Antenna Television

Part 4: Format and General Arrangement

1. The numbering system used to identify sections and rules in the codebook is as follows. Even numbers (not odd numbers) have been used to identify sections and rules. Rule numbers consist of the section number separated by a hyphen from the 3- or 4-digit figure.

2. Odd numbers may be used for new rules required by interim revisions.

3. The rule numbers sometimes change from one edition to another due to the introduction of some new rules and the deletion of some existing rules.

4. The rules in the codebook are arranged as follows:

00-000: Rule
(1): Sub-Rule
(a): Item
(i): Item
(A): Item

5. Rules that are new or revised from the previous edition of the textbook are marked in the text of the code by the symbol delta (Δ) in the margin.

6. The “General Sections” of the code include sections 0-16 and 26.

7. Sections of the code that are not the general sections are called supplements or amendments.

8. Three reasons why code rules may be added, revised or changed include:

- Harmonization with the National Electrical Code (U.S.A.)
- New technology in the workplace.
- Industry practices.

9. The three types of information found in the table of contents include:

- Section Titles/Headings
- Page Titles/Sub-Headings
- Page Numbers

10. Commonly used units and their conversion factors from Metric to Imperial and vice versa can be found in the table on page xxvi.

11. The conduit sizing shows the metric trade designator first, with the value in inches following in parentheses.

2. Forward bias is the application of the proper polarity to a semiconductor diode. This results inforward current.

3. Reverse bias is when the opposite polarity is applied to a semiconductor diode. It results in a reverse current either close to zero or extremely small (i.e. a millionth of an ampere).

4. The electrons in the current flow through the diode by means of traveling from the cathode to the anode.

5. The simplest form of a rectifier circuit is the half-wave rectifier.

6. A rectifier is a circuit that converts AC power into DC power.

7. A semiconductor is a material that has a resistance to current flow between the low resistance offered by a conductor and the high resistance offered by an insulator.

8. A semiconductor is doped by replacing some of the atoms in the crystal (i.e. germanium and silicon) with atoms from other elements.

9. N-type material is created by doping a region of a crystal with atoms from an element that has more electrons in its outer shell than the crystal. This results in more free electrons and thus a negative charge. P-type material is created by doping a crystal with atoms from an element that has fewer electrons in its outer shell than the natural crystal. This results in empty spaces forming in the crystalline structure that are represented as positive charges.

10. Carriers are free electrons that help move current.

11. An operating characteristic curve shows the relationship between voltage and current for a typical diode. Manufacturers often supply these to show how certain diodes operate and to provide information concerning the specifications of the diodes.

12. Peak Inverse Voltage is a rating for a diode regarding the maximum reverse bias voltage it can withstand.

13. Using an ohmmeter, a diode can be tested for opens, shorts and its polarity.
14. When using an ohmmeter, precautions include: reading the manual (to check internal
polarities), not applying power to the circuit, and making sure that the diode is disconnected from the circuit to avoid interference from any parallel circuitry.

15. When installing diodes, special precautions include: observing voltage specifications, double checking circuits/polarities/component sizes/wiring before installation (to prevent an
overload), properly fastening/securing stud-mounted diodes, applying silicon grease and
taking precautionary measures when using soldering irons.

16. The power capacity of a diode is the maximum current at which it may operate in a normal environment. The power capacity of most diodes is rated at an operating temperature of 25°C.

Sodium was discovered by Sir Humphry Davy of Britain in 1807. It comes from the word "soda", which is sometimes used to describe various sodium compounds and "natrium". Its symbol is Na. It belongs to the group 1 of the periodic table and is one of the alkali metals. Its atomic number is 11.

Sodium is a very essential part of plants and animal tissues. The most common compound is sodium chloride, which is our ordinary table salt. Sodium or soap is generally a sodium salt of fatty acids. Sodium's liquid metal is used as a heat exchanger in certain nuclear reactors. It floats on water and may or may not ignite spontaneously on the water. Pure sodium is dangerous as it is poisonous and is very corrosive.

Sodium can be used as an ordinary table salt (sodium chloride). It is also used in soda, glass, as metal purifier, soap, paper and textile.

Potassium

Potassium is a very important element of all living things most especially to human beings. It is has good health benefits to the human body most especially to people with heart problems. As an element, it is a silvery white metal and can be cut with a knife. It is the lightest known metal and reacts rapidly to release hydrogen when in water, which burns with a lilac flame. It is a prime element in fertilizers eventhough it is slightly radioactive.

The symbol of Potassium is K. It comes from the words "potash" and "kalium". It belongs to the group one of the periodic table and is one of the alkali metals. It was discovered by Sir Humphry Davy of Britain in 1807. A potassium compound was originally obtained by soaking wood ash in a pot of water and allowing the water to evaporate. It is a chemically reactive and extremely soft metallic element.

Potassium is used in fertilizers, as a heat transfer agent, "strike anywhere" matches, fireworks and explosives.

The symbol of Chromium is Cr. This element is one of the transition elements of the periodic table. It is a gray metallic element that can take on a high polish. It is steel-gray, lustrous, metallic and can be found as chromite ore. Its compounds are toxic.

Chromium was discovered by the French chemist Louis Nicolas Vauquelin, who named it chromium in 1797. It's compounds has many different colors and so it was named from the Greek word "chroma" which means color.

Cadmium

Cadmium comes from the Latin word "kadmia"which means earth. Its symbol is Cd. Cadmium was discovered by the German chemist Friedrich Stromeyer in 1817 who found it in incrustations in zinc furnaces. This element is one of the transition elements in group 12 of the periodic table.

Cadmium is a silvery-white metallic element produced as a by-product of zinc refining that can easily be shaped. It's a soft, bluish-like metal and is easily cut with a knife. Cadmium and its compounds are highly toxic. It occurs in nature with zinc. It burns in air with a bright light when heated. It is poisonous and can cause birth defects and cancer. It generally tarnishes in air, is soluble in acids but not in alkalis.

Cadmium is used for rechargeable batteries, bearings, electroplating, solder, TV phospors. It is important to note that silver solder, which contains cadmium, should be handled with care.

Curium

The symbol of Curium is Cm. It was discovered in 1944 and was named for Pierre and Marie Curie, research pioneers in radioactivity. American chemists Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso first introduced this element.

Curium is one of the transuranium elements in the actinide series of the periodic table. It is a radioactive element and is a heavy metal similar in properties to uranium, plutonium and americium.

Curium is radioactively unstable and does not exist in nature. It is made by bombarding synthetic plutonium with accelerated particles. It is a decay product of americium. It is used in satellite technology and also as a power source.

To start out, convection is heat transfer through a fluid (liquid and gas). Convection happens when a fluid is heated. The part nearest the heat source expands. The kinetic energy increases as molecules move faster and contract. The heated fluid becomes less dense. Density is the amount of mass in a volume. The fluid is forced to rise because it is less dense than the cooler, more compact fluid. When it reaches the surface, the warmer liquid starts to diffuse and expands to the sides. At the surface, it cools down and the fluid sinks. The heat source then reheats the liquid. The liquid then goes over the same process over and over again. These are called convection currents. Convection currents continue until the heat source has been removed and the molecules are the same temperature. Convection currents are a chain of movement by heat through a liquid when there is a heat source. Unlike radiation, convection can be visible sometimes. Convection, along with radiation and conduction happen near earth’s surface. Convection, conduction and radiation all involve a heated object. Convection does not transfer heat through electromagnetic waves. Some examples of convection are in the asthenosphere, troposphere, and even at homes. In the asthenosphere (a layer between 100-200 miles below the earth’s crust, right above the mantle) the magma in the asthenosphere which is nearest the mantle rises because it is heated by the mantle. Once it reaches the top, it expands to the sides, the fluid sinks, the fluid gets heated again. Convection causes more warming than radiation and conduction in the troposphere (the lowest layer of atmosphere). The air near the ground gets heated and the molecules have more kinetic energy. They crash into each other and expand farther out. When it moves farther out, it becomes less dense. The cooler more dense air stays at the bottom, while the warmer flows into the troposphere. Some home appliances that involve convection are heaters and refrigerators. Heaters are a combination of both convection and radiation. The heater sends out electromagnetic waves which is radiation. The heat which escapes from the heat sources is force to rise because it is less dense than the cooler air around it. At the top of the house, it expands towards the sides, it starts to cool, and then it sinks as the heater heats the air again. Refrigerators use convection currents in order to stay cool. There is a heat absorber on the bottom and a cooler on the top. The warmer air rises through narrow tube and it goes to the cooler on the top. Once it cools, it goes through an open place where the food is. It cools the food as the cool air sinks down. It is then heated again and continues in the repeating cycle again and again.

In addition, radiation is another way of heat transfer. Radiation is the transfer of heat in contact with electromagnetic waves through an empty space. Unlike radiation and convection, radiation does not involve direct contact between molecules. Radiation is the only form of heat transfer which can cross a vacuum (a space which is empty of matter).It is also the only form of heat transfer which transfers by waves. There are many types of radiation. One is infrared radiation. Infrared radiation travels directly to an object. Infrared radiation causes the greatest temperature increase. Examples of infrared radiation is heat from the sun, heaters, lamps, light bulbs, etc. The sun’s radiation is mostly made out of visible light radiation and infrared radiation. A small portion is also made out of ultraviolet radiation, a very dangerous type of radiation. An effect which infrared radiation causes is the greenhouse effect. When heat enters a space, only 50 percent of the heat can escape. This is the cause of global warming.

Furthermore, conduction is another form of how heat can be transferred. Conduction is heat transfer by direct contact within particles of matter. Conduction can only be transferred through solids unlike convection. The energy nearest the heat source increases, the particles start vibrating and spread on some of their energy, spreading heat through the whole solid. Unlike radiation, conduction needs direct contact with particles. Both conduction and convection need matter to transfer heat. Metals are good conductors because they have freely moving electrons which pass energy more efficient. Substances that conduct heat slowly are called insulators.  Wood and water are examples of insulators. An example of conduction uses a pan, some water, and a metal spoon. Once after some time, the metal spoon gets heated by conduction because particles near the bottom vibrate faster when they are heated, they bump into cooler molecules. Eventually, the whole spoon heats up. Another example of conduction is the desert. The sun heats up the top layer of sand on the desert, so it becomes extremely hot. When someone steps on the sand, conduction transfers some of the heat to the barefoot of the person. When someone is wearing a leather shoe, it is a better insulator then a regular foot so it takes longer for it to heat up. The molecules gain energy every time they pass some energy to nearby molecules. The ability to transfer heat within an object is called thermal conductivity.

Clearly, conduction, convection, and radiation are the ways heat can be transferred from warmer to cooler object.  The three types of heat transfer each have their very own unique characteristics. The type of heat transfer will vary because of the substance (fluid or solid) and how heated is transferred.

The Scientific Method

The Scientific Method is a logical approach to solving problems by observing and collecting data, formulating hypotheses, testing hypotheses, and formulating theories that are supported by data.

Steps in the Scientific Method include:

• Purpose

First, state the problem. What are you looking for or trying to find in the experimentation? Ask a question that can be answered through the experimentation. For example, if the experiment deals with plant growth, a question would be, “Does nitrogen fertilizer really help plants grow higher and greener?” and the purpose would be to gain knowledge so that you may start the process at home, or that you are simply curious and want to find out.

• Background Information

Research the topic in which the experimentation is going to take place so that you can have a general idea and make the predictions and inferences. It is important to research the topic so that you have prior knowledge to analyze the data with after experimentation.

• Form a hypothesis

The hypothesis is a testable statement that may include a prediction. It is usually in the form of an if-then statement, but it does not have to have the words “if” or “then.” It should have a possible explanation to a phenomenon. The hypothesis should not be confused with a theory.

• Materials and Procedures

List the materials needed and have them ready for use. Conduct a procedure that would guide through the experimentation. It should be a systematic process to complete the experiment with ease and precision.

• Test the hypothesis

This is where the main experimentation comes in. In this step, you are observing different variables and testing the hypothesis. Making observations is important in the experimentations. Observations may include drawing pictures, taking notes, or simply describing what is going on in the experiment. The independent variable in the experiment is the variable that you control. For example, if an experiment deals with plant growth. The amount of time of sunlight given to the plant would be the independent variable because you can control the amount of time of sunlight to give the plant. The dependent variable is the variable that is dependent upon the independent variable. The dependent variable is the change that is caused by the independent variable. For example, the growth of the plant under the sun is the dependent variable because the plant changes its height due to the amount of time in the sunlight. The control variable is anything in the experiment that has not been changed. There could be multiples of dependent variables, but there is only one independent variable in the experiment.

• Recording and Analyzing the Data

Record the data from the observations made, by forming a data table and graph. Make sure that other people can understand the information from the experiment. Take note on what is quantitative and qualitative. Quantitative deals with numbers, hence the root, quantity. For instance, there were two eyes on the frog, or there were two legs and two arms on a frog. Qualitative deals with the quality of data from the experiment. For example, the frog was green and had brown spots on its back, or the frog's heart was small and pink. Analyze the data by discussing what the data illustrated. If any question were provided, answer them with detail. If not, then create your own questions by going in depth and include information from the background research because this will help you test your knowledge about the topic. Analyze the graph from the data. Is there enough information to know whether the hypothesis is correct? Is the data correct and accurate? Are there any patterns present? These are key questions to help analyze the data from the experimentation.

• Conclusion

The conclusion is the summary of the experiment and states whether the hypothesis was proved or disproved. State whether the hypothesis was correct in the experiment. If it was, explain how the hypothesis was correct by summarizing what has happening in the experiment, using details and support from observations and data. State what you have learned in the experiment and how you can have done differently in the future. If the hypothesis was disproved in the experimentation, state it, and give the results from the data. State what you could have done differently so that you can improve the experiment in the future. Give possible reason why the experiment did not support the hypothesis. State unavoidable errors and other errors that could have occurred in the experiment, because when recording findings, this information may influence the result.

Measurements in Chemistry

Measurements describe quantities, which is a property that can be measured by a number and a unit that names the standard use.

For example: 10 and 25 are numbers

10cm and 25kg are quantities

A quantity is not the same as a measurement because the quantity that is represented by a liter is volume. A liter is a unit of measurement, while volume is quantity. Quantities require units and as in math, only like quantities can be added or subtracted.

For example: Add 2 hours and 27 minutes. The sum is not 27 hours or 27 minutes, so the units must be changed so they are the same: 120 minutes (2 × 60 minutes) + 25 minutes = 145 minutes. In science, scientists all over the world use the SI system. It is abbreviated from the French term, Le Système International d'Unités, which stands for The International System of Unites. This system is very popular because it uses the same numerical base as the decimal number system, in which every unit in the system is ten times the size of the next smaller units. In other words, it is the modern form of the metric system.

Scientific Notation

Many calculations in science involve very large numbers or very small numbers. These numbers involve large strings of zeros. To facilitate these calculations, a number between 1 and 10 is multiplied by some power of 10. This form is called the scientific notation and the parts include:

1.5 × 103 where 1.5 is the decimal part and 103 is the exponential part.

A power is a product obtained by multiplying together two or more equal factors, for example: x4. An exponent, also called an index, is the name given to the number that indicates the number of factors that have been multiplied together to produce the power.

For example: The exponent 4 indicates a4 = a × a × a × a.

Contrast the scientific notation with expanded notation, which is the form most people are used to using, where the numbers are written in their expanded form.

For example: 1.5 × 103 = scientific notation

1500 = expanded notation

The laws that govern the use of exponents (or indices) that are used frequently are:

Law of Multiplication: xm × xn = xm+n

For example: 103 × 104 = 107

Law of Division: xm ÷ xn = xm−n

For example: 107 ÷ 102 = 105

Law of Powers: (xm)n = xm×n

For example: (105)3 = 1015

Negative exponents are defined by the formula: x-m = 1/xm For example: 10-1= 1/10 = 0.1

Exponential notation, another name of scientific notation, also expresses any number as a product of a number between 1 and 10 and an integral power of 10.

For example: 275 = 2.75 × 100 = 2.75 × 102

0.00043 = 4.3 × 1/1000 = 4.3 × 10-4

The rule for converting decimal fractions to exponential notation is that it always have negative powers of 10 and the absolute value of the exponent is always one greater than the number of zeros immediately after the decimal point.

British educator and philosopher Joseph Priestley (1733 - 1804) discovered oxygen in experiments, isolated the gas, and described its function in combustion and respiration. He also invented soda or carbonated water by dissolving fixed air with water. Unaware of the significance of his discoveries and because of his stubborn refusal to abandon the phlogiston theory, he named the new gas "dephlogisticated air." However, it would be the French chemist Antoine Lavoisier (1743 - 1794) who gave the gas its present name, and was able to explain the nature of the element, accurately describing its role in combustion that totally discredit the phlogiston theory. In addition, Lavoisier collaborated with others to develop a systematic chemical nomenclature that facilitates dialogue among chemists and is still very much in use today.

Atomic Theory (1800s)

John Dalton (1766 - 1844), English chemist and physicist, proposed the atomic theory, which states that: a.) all elements are made up of tiny particles called atoms; b.) all atoms of an element are identical; c.) the atoms of dissimilar elements can be distinguished from one another by their corresponding relative weights; d.) atoms of an element can be combined with atoms of another elements to form chemical compounds; and e.) atoms cannot be created, broken down into smaller particles, nor destroyed in a chemical process. He also presented a way of associating invisible atoms with quantifiable amounts such as mass of a mineral or volume of a gas. Dalton's theory has undergone modifications through the centuries, but it has as much significance for the future of the science as Lavoisier's oxygen-based chemistry had been.

Molecules are Made Up of Atoms (1810s - )

At a time when the words "atom" and "molecule" were used interchangeably, Italian scientist Amedeo Avogadro (1776 - 1856) clarified that atoms combine to form molecules; and proposed his eponymous principle which asserts that "Equal volumes of ideal gases, at the same conditions of temperature and pressure, contain equal numbers of particles or molecules."

The Electron (1890s)

Through a series of experiments using cathode ray tubes, J. J. Thomson (1856 - 1940) discovered that cathode rays emitted negative charged particles, a component that makes up atoms. He called these particles "corpuscles," now known as electrons. He proposed that plum pudding model, in the belief that atoms consisted of an abundance of these corpuscles teeming in an ocean of positive charged particles; but this was subsequently proven to be erroneous when Ernest Rutherford (1871 - 1937) developed the orbital theory of the atom and discovered through his famous gold foil experiment that atomic masses are largely concentrated in the nucleus surrounded by electrons.

Electrons for Chemical Bonds (1910s - )

On the foundation of Ernest Rutherford's theories, Danish physicist Niels Bohr (1885 - 1962) published his atomic structure model, postulating that electrons move in specific orbits around the nucleus; and that the chemical properties of an element are largely dependent of the number of electrons in the outer orbit. These discoveries led the way to a greater understanding of the physical interactions between atoms and molecules, a process called chemical bonding.

Periodic Table of the Elements (1860s - 1870s)

Russian chemist and inventor Dmitri Mendeleev (1834 - 1907) discovered that if he tabulize the sixty-three known elements in order of increasing atomic number, their chemical properties recur in periodic cycles. So he devised the periodic table of the elements that successfully predicted the existence of yet undiscovered elements. In fact, three were found in his lifetime: scandium, germanium and gallium. The design of the table has been refined and expanded as new elements are discovered, making it absolutely essential to the academic discipline of chemistry, and at the same time, supplying a very valuable tool in classifying, systematizing and studying different chemical behaviors.

Urea Synthesis (1820s)

Friedrich Wöhler (1800 - 1882), German physician and chemist, accidentally synthesized an organic substance, urea, from inorganic matter; and as a result, unintentionally overthrew vitalism, the belief that chemicals released by living organisms are essentially different from non-living things. His discovery started the new subfield of organic chemistry.

Chemical Structure (1850s)

Following years of researching carbon-carbon bonds, German organic chemist Friedrich Kekule (1829 - 1896) suggested that the chemical structure of benzene as a ring-shaped arrangement of six carbon atoms after having dreamt of a snake grasping its own tail. The structure explained the difficulty why carbon atoms have the ability to bond up to four atoms simultaneously, a property known as tetravalence. Kekule, with the breakthrough of his theory of chemical structure, led to a greater understanding of molecular structure and resulted in the explosive development of the field of organic chemistry.

Electrolysis (1800s)

Having discovered that electricity can alter chemicals, British inventor Humphry Davy (1778 - 1829) pioneered the use of electrolysis as a method for splitting up chemical compounds into their constituent parts by passing an electric current through them. With numerous batteries used in electrolysis, he discovered several new elements: potassium, sodium, strontium, boron, magnesium and barium.

Atoms Have Signatures of Light (1850s)

German physicist Gustav Kirchhoff (1824 - 1887) and chemist Robert Bunsen (1811 - 1899) worked together in a field called spectrum analysis and learned that every element either absorbs or releases light at discrete wavelengths, producing discrete spectral lines. Though Kirchhoff and Bunsen did not understand about the existence of energy on the atomic level, the existence of spectral lines was satisfactorily explained by the Bohr's atomic model, leading to the development of a completely new field called quantum mechanics.

Radioactivity (1890s - 1900s)

Marie (1867 - 1934) and Pierre Curie (1859 - 1906) were able to extract uranium from pitchblende, and noted that the pitchblende seem to be more active than what they had extracted. They deduced that the ore, aside from uranium, contain traces of an unknown substance or element that are radioactive. Their study led to the discovery of new elements, which they dubbed as polonium and radium.

Plastics (1860s, 1900s)

In 1869, American inventor John Wesley Hyatt (1837 - 1920) was able to develop a commercially viable way of producing celluloid plastic in his effort to find an ivory substitute for manufacturing billiard balls. Celluloid became the first synthetic plastic and was utilized as a replacement for more expensive materials as ivory, amber and tortoiseshell. By the first decade of the twentieth century, Belgian-born American chemist Leo Baekeland (1863 - 1944) invented the first hard moldable plastic called Bakelite, a synthetic substitute characterized by insulating and heat-resistant properties. Soon it permeated almost every branch of industry, and became a ubiquitous presence in nearly every object in society. However, the use of plastics has raised serious environmental concerns in the last few decades.

Fullerenes (1980s)

Chemists Robert Curl (1933 - ), Harold Kroto (1936 - ) and Richard Smalley (1943 - 2005) discovered a very stable although not necessarily unreactive form of carbon with cage-like molecular structure. Other carbon compounds of similar structure have also been discovered and are collectively known as buckminsterfullerenes or fullerenes. The structures are made up entirely of carbon molecules arranged in spherical, ellipsoidal, tubular or ring-shaped form. The term was named after Richard Buckminster Fuller (1895 - 1983), who was an architect best known for creating geodesic-domed structures in the mid-twentieth century, which are sometimes referred as buckyballs.

Click on the following for more Greatest Discoveries series in the fields of:

• Astronomy
• Biology
• Earth Sciences
• Genetics
• Medicine and
• Physics

The two disciplines with the largest impact were chemistry and biology. The name attached to agricultural chemistry is Justus von Liebig, a German chemist who in the 1840s formulated a theory on the processes underlying soil fertility and plant growth. He propagated his organic chemistry as the key to the application of the right type and amount of fertilizer. Liebig launched his ideas at a time when farmers were organizing themselves based on a common interest in cheap supplies. The synergy of these developments resulted in the creation of many laboratories for experimentation with these products, primarily fertilizers. During the second half of the nineteenth century, agricultural experiment stations were opened all over Europe and North America.

Sometime later, experimental biology became entangled with agriculture. Inspired by the ideas of the British naturalist Charles Darwin, biologists became interested in the reproduction and growth of agricultural crops and animals. Botany and, to a lesser extent, zoology became important disciplines at the experimental stations or provided reasons to create new research laboratories. Research into the reproductive systems of different species, investigating patterns of inheritance and growth of plant and animal species, and experimentation in cross-breeding and selection by farmers and scientists together lay the foundations of genetic modification techniques in the twentieth century.

By the turn of the century, about 600 agricultural experiment stations were spread around the Western world, often operating in conjunction with universities or agricultural schools. Moreover, technologies that were not specifically developed for agriculture and food had a clear impact on the sector. Large ocean-going steamships, telegraphy, railways, and refrigeration, reduced time and increased loads between farms and markets. Key trade routes brought supplies of grain and other products to Europe from North America and the British dominions, resulting in a severe economic crisis in the 1880s for European agriculture. Heat and power from steam engines industrialized food production by taking over farm activities like cheese making or by expanding and intensifying existing industrial production such as sugar extraction. The development of synthetic dyes made crop-based colorants redundant, strongly reducing or even eliminating cultivation of the herb madder or indigo plants. These developments formed the basis of major technological changes in agriculture and food through the twentieth century.

Photosynthesis takes place in the chloroplasts (an organelle in the plant cell) of the plant, usually the ones in the leaves. The chloroplasts contain chlorophyll. Chlorophyll is what absorbs the light energy into the plant so it plays an essential role in the process of photosynthesis.

The process of photosynthesis involves many different chemical reactions, each triggering the next reaction along the line. Photosynthesis in plants involves the conversion of light energy, water and carbon dioxide into glucose and oxygen.

The glucose is used by the plant as energy so it can survive. The water is usually absorbed by the plant through its roots while the light energy (photons) and carbon dioxide are absorbed by the plant through its leaves. A popular simplified equation of how photosynthesis works is:

Six molecules of carbon dioxide + Twelve molecules of water + Photons -> One molecule of sugar/glucose + Six molecules of oxygen gas + Six molecules of water

or

6 CO2 (g) + 12 H2O (l) + photons -> C6H12O6 (aq) + 6 O2 (g) + 6 H2O (l)

In total, there are two main steps in photosynthesis. The first step is where the light energy is used to high energy molecules such as ATP (Adenosine Triphosphate) and NADPH (Nicotinamide Adenine Dinucleotide Phosphate). ATP is a substance which is part of the animal and plant cells and helps provide the cell with energy. The above step is usually called Light Reactions. The second step, the Calvin-Benson Cycle, involves the ATP and NADPH produced in step 1 being used to turn the carbon dioxide absorbed by the plant into G3P (glyceraldehyde 3-phosphate). When two molecules of 3GP join together, it forms glucose.

In step 1, the chlorophyll absorbs the photons (light). In doing so, the chlorophyll loses one electron. This causes a chain reaction and starts a flow of electrons through various substances until NADP+ is reduced to NADPH (NADP gains one electron which was lost by the chlorophyll - NADPH is reduced form of NADP+ while NADP+ is the oxidized form of NADPH - OILRIG ). This process also helps create ATP. The chlorophyll molecule gets its electron back by taking one off water. The water then turns into oxygen gas. The hydrogen in NADPH comes from the water molecule as well. ADP (adenosine diphosphate) and Pi (inorganic phosphate) are chemicals involved in the formation of ATP. The formula for this is:
Two molecules of water + Two 1+ charged ions of NADP + Two molecules of adenosine diphosphate (ADP) + Two molecules of inorganic phosphate + photons -> Two molecules of NADPH + Two 1+ charged ions of hydrogen + Two molecules of ATP + One molecule of

oxygen gas

or

2 H2O + 2 NADP+ + 2 ADP + 2 Pi + light → 2 NADPH + 2 H+ + 2 ATP + O2

Step 2 of photosynthesis, the Calvin-Benson Cycle, is where the NADPH and ATP molecules undergo a process called carbon fixation on the carbon dioxide gas absorbed by the plant. The carbon dioxide is chemically reduced into the precursors of carbohydrates. In this reaction, the enzyme RuBisCo captures carbon dioxide from the air. Then ATP and NADPH turn it into G3P (glyceraldehyde 3-phosphate or C3H5O3-PO32-). Water is also involved in the reaction, helping form G3P (hydrogen in G3P is from water). The other molecules produced in this reaction like H+, NADP+, ADP and Pi are recycled and used again in step 1 of photosynthesis while the G3P combines with another one so that it has a full outer shell of electrons. This product is sugar. The equation for this is:

Three molecules of carbon dioxide + Six molecules of NADPH + Five molecules of water + Nine molecules of ATP -> One molecule of 2- charged G3P + Two 1+ charged ions of hydrogen + Six 1+ charged ions of NADP + Nine molecules of ADP + Eight molecules of inorganic phosphate

or

3 CO2 + 6 NADPH + 5 H2O + 9 ATP → C3H5O3-PO32- + 2 H+ + 6 NADP+ + 9 ADP + 8 Pi