Monday, July 30, 2007

Significant Figure Rules

i. Rule 1: All nonzero digits are significant.

Ex. 12, 235 = 5 significant digits

i. Rule 2a: Zeros are significant when found between 2 nonzero digits.

Ex. 250.6 = 4 significant digits

ii. Rule 2b: Zeros are significant when found after a decimal point.

Ex. 5.00 = 3 significant digits; 2.0 = 2 significant digits

iii. Rule 2b: Zeros are significant when found after a nonzero digit in a decimal number.

Ex. 5.030 = significant digits

iv. Rule 3a: Zeros are not significant when used as a place indicator. …

Ex. 0.003 = 1 significant digit

v. Rule 3b: Zeros are not significant when used to call attention to a decimal point. …

Ex. 0.003 = 1 significant digit

vi. Rule 4: Zeros at the end of a number without a decimal point may or may not be significant. We remove the ambiguity by using scientific notation.

Ex. 30, 000 = 1, 2, 3, 4, or 5 significant digits;

3 x 104 = 1 significant digits

3.0 x 104 = 2 significant digits

3.00 x 104 = 3 significant digits

3.000 x 104 = 4 significant digits

3.0000 x 104 = 5 significant digits

Laboratory Guidelines

General Guidelines

a. Conduct yourself in a responsible manner at all times in the laboratory.

b. Be familiar with your lab assignment before you come to lab. Follow all written and verbal instructions carefully. If you do not understand a direction or part of a procedure, ask the teacher before proceeding.

c. Never work alone. No student may work in the laboratory without an instructor present.

d. When first entering a science room, do not touch any equipment, chemicals, or other materials in the laboratory area until you are instructed to do so. \

e. Do not eat food, drink beverages, or chew gum in the laboratory. Do not use laboratory glassware as containers for food or beverages.

f. Perform only those experiments authorized by the instructor. Never do anything in the laboratory that is not called for in the laboratory procedures or by your instructor. Carefully follow all instructions, both written and oral. Unauthorized experiments are prohibited.

g. Observe good housekeeping practices. Work areas should be kept clean and tidy at all times. Bring only your laboratory instructions, worksheets, and/or reports to the work area. Other materials (books, purses, backpacks, etc.) should be stored in the classroom area.

h. Know the locations and operating procedures of all safety equipment including the first aid kit, eyewash station, safety shower, spill kit, fire extinguisher, and fire blanket. Know where the fire alarm and the exits are located.

i. Be alert and proceed with caution at all times in the laboratory. Notify the instructor immediately of any unsafe conditions you observe.

j. Labels and equipment instructions must be read carefully before use. Set up and use the prescribed apparatus as directed in the laboratory instructions provided by your teacher.

k. Keep hands away from your face, eyes, mouth, and body while using chemicals. Wash your hands with soap and water after performing all experiments. Clean (with detergent powder), rinse, and dry all work surfaces and equipment at the end of the experiment.

l. Experiments must be personally monitored at all times. You will be assigned a laboratory station at which to work. Do not wander around the room, distract other students, or interfere with the laboratory experiments of others.

m. If you spill acid or any other corrosive chemical on you skin or clothes immediately wash area with large amounts of water (remember that small amounts of water may be worse that no water at all). After this get the teacher’s attention. The spill kit will be used for spills on floor or counter-top.

n. At the end of the laboratory session see that: a) main gas outlet valve is shut off b) the water is turned off c) desk top, floor area, and sink are clean d) all equipment is cool, clean, and arranged.


a. Dress properly during a laboratory activity. Long hair, dangling jewelry, and loose or baggy clothing are a hazard in the laboratory. Long hair must be tied back and dangling jewelry and loose or baggy clothing must be secured. Shoes must completely cover the foot. No sandals are allowed.

Accidents and Injuries

a. Report any accident (spill, breakage, etc.) or injury (cut, burn, etc.) to the instructor immediately, no matter how trivial it may appear.

b. If a chemical should splash in your eye(s), immediately flush with running water from the eyewash station for at least 20 minutes. Notify the instructor immediately.

Handling Chemicals

a. All chemicals in the laboratory are to be considered dangerous. Do not touch, taste, or smell any chemical unless specifically instructed to do so. The proper technique for smelling chemical fumes (when instructed to do so by the teacher) is to gently fan the air above the chemical toward your face. Breathe normally.

b. Check the label on chemical bottles twice before removing any of the contents. Take only as much chemical as you need. Smaller amounts often work better than larger amounts. Label all containers and massing papers holding dry chemicals.

c. Never return unused chemicals to their original containers.

d. Never use mouth suction to fill a pipet. Use a pipet bulb or pipet filler.

e. Acids must be handled with extreme care. ALWAYS ADD ACID SLOWLY TO WATER, with slow stirring and swirling, being careful of the heat produced, particularly with sulfuric acid.

f. Handle flammable hazardous liquids over a pan to contain spills. Never dispense flammable liquids anywhere near an open flame or source of heat.

g. Never take chemicals or other materials from the laboratory area.

h. Take great care when transferring acids and other chemicals from one part of the laboratory to another. Hold them securely and in the method demonstrated by the teacher as you walk.

Heating Substances

a. Never leave a lit burner unattended. Never leave anything that is being heated or is visibly reacting unattended. Always turn the burner or hot plate off when not in use.

b. You will be instructed in the proper method of heating and boiling liquids in test tubes. Do not point the open end of a test tube being heated at yourself or anyone else.

c. Heated metals, glass, and ceramics remain very hot for a long time. They should be set aside to cool on a trivet and then picked up with caution. Use tongs or heat-protective gloves if necessary. Determine if an object is hot by bringing the back of your hand close to it prior to grasping it.

foreign chemist

Democritus (460-370B.C.)

-Greek philosopher, Developed atomic theory, -Elaborated idea that matter consisted of atoms having physical size and shape which constantly moved in a void and interacted in different ways

Daniel Rutherford (1749-1819)

-Discovered Nitrogen through experimentation with a mouse, a candle, and burning phosphorus

Robert Boyle (1627-1691)

-English physicist and chemist, Experimented in pneumatics (the study of mechanical properties of air and other gases), Through research he rejected the accepted definition of matter, -Proposed Boyle’s Law (1662)

Henry Canvendish (1731-1810)

-English physicist and chemist, Discovered hydrogen (1766), Discovered nitric acid

John Dalton (1766-1844)

-English chemist and physicist, Professor of mathematics and natural philosophy (1793), Developed atomic theory, His theory (1805) accounts for the law of conservation of mass, law of definite proportions, and law of multiple proportions, Produced the first table of atomic weights

Amedeo Avogadro (1776-1856)

-His hypothesis stated that equal volumes of gases, at the same temperature and pressure, had the same amount of molecules, Avogadros number is 6.022e23, meaning that exactly 12 grams of carbon 12 has exactly 6.022e23 carbon atoms

Joseph Louis Gay-Lussac (1778-1850)

-French chemist and physicist, Developed the law of volumes concerning the combination of gases, Discovered Boron

Robert Wilhelm Bunsen (1811-1899)

-German chemist, Helped develop the spectroscope, Introduced the Bunsen burner that was actually developed by his laboratory assistant, Peter Desaga, Discovered elements Cesium and Rubidium

Dmitri Ivanovich Mendeleev (1834-1907)

-Russian chemist, Developed the periodic table by placing the elements in order of increasing atomic weight (1869), Predicted the existence and properties of elements that would fill the gaps left in his chart (1871), These elements were discovered between 1875 and 1885

Joseph John Thomson (1856-1940)

-English physicist, Researched atomic structure, Discovered that atoms contained particles which he called "electrons" by testing the ratio of cathode ray particles to their mass and found out that they were always the same. The tube was full of negatively charged particles eventually from his name called electrons., Developed the "plum pudding" or "raisin muffin," model of the atom which consisted of electrons embedded in a positive sphere of matter (1904), Received Nobel Prize for physics (1907), Developed the mass spectrograph with Francis William Ason (1919)

Robert Andrews Milikan (1868-1953)

-American physicist, Succeeded in measuring, quite accurately, the minimum electric charge that could be carried by a particle (1911), Found charge of an electron through oil-drop experiment, Made an apparatus that allowed drops of oil to fall between two electrically charged plates, He monitored the drops and measured how the voltage affected their rate of fall, From this, he calculated the charges on the drops, which were always multiples of 1.60E-19C, This number, he found, is the charge of one electron

Ernest Rutherford (1871-1937)

-British physicist from New Zealand, Discovered several radioactive isotopes with colleagues (1899-1905), Classified forms of radiation as alpha, beta, and gamma; received Nobel Prize for chemistry (1908), Worked on submarine detection during WWII, Developed atomic theory (1911), Researched Transmutational effects of alpha particles on gases (1919) and other elements, Performed the "gold-foil" experiment which he used piece of gold foil and shot positively charged particles at it to find other parts of the atom, Almost all of the particles shot through the foil but some "larger particles" shot back, He called the central part of the atom the nucleus

Gilbert Newton Lewis (1875-1946)

-American physical chemist, Developed atomic theory, Proposed the octet rule and the electron dot method of showing valence electrons, Important contributor to acid-base theory and thermodynamics,

Niels Henrik Bohr (1885-1962)

-Danish physicist, His model of atomic structure (Bohr Model) proposed that electrons orbit the nucleus in fixed orbits that are discrete energy states, Received the Nobel Prize for physics for his work in atomic structure and radiation (1922),

Henry Moseley (1887-1915)

-English physicist, Discovered Moseley's law of characteristic X-ray spectra of elements (1913), Demonstrated that the number of electrons in an element is the same as the atomic number, establishing the significance of the atomic number

Erwin Schroedinger (1887-1961)

-Austrian physicist, Developed atomic theory of wave mechanics (1926)

-Shared Nobel Prize for physics with P.A.M.Dirac (1933)

James Chadwich (1891-1974)

-English physicist, Discovered the neutron, Received the Nobel Prize for physics for this discovery (1935),

Louis-Victor de Broglie (1892-1958)

-French physicist, Demonstrated mathematically that electrons and other subatomic particles exhibit wavelike properties, Received Nobel Prize for physics (1929)

Linus C. Pauling (1901-1994)

-American biochemist, Applied X-ray diffraction, electron diffraction and quantum mechanics to chemistry, Developed theories of rare gas compounds; developed mechanistic theory of enzymes (1946), Determined the physical structure of proteins as helical (1951), Developed and applied some of the laws of structural chemistry in work with proteins, Researched the structure of DNA, Received Nobel Prize for chemistry (1954) for research of the nature of chemical bonds, Received Nobel Prize for peace (1962) for work in banning nuclear weapons testing, Received National Medal of Honor (1975), Shared in the quantum mechanical development of valence and resonance theory, Introduced concept of electronegativity, Founded the Linus Pauling Institute of Science and Medicine (1973), Researched Vitamin C and nutrition

Tasks of a chemist

A chemist has several tasks

1. Analyze organic and inorganic compounds to determine chemical and physical properties, composition, structure, relationships, and reactions, utilizing chromatography, spectroscopy, and spectrophotometry techniques.

2. Induce changes in composition of substances by introducing heat, light, energy, and chemical catalysts for quantitative and qualitative analysis.

3. Develop, improve, and customize products, equipment, formulas, processes, and analytical methods.

4. Compile and analyze test information to determine process or equipment operating efficiency and to diagnose malfunctions.

5. Study effects of various methods of processing, preserving, and packaging on composition and properties of foods.

6. Prepare test solutions, compounds, and reagents for laboratory personnel to conduct test.

7. Confer with scientists and engineers to conduct analyses of research projects, interpret test results, or develop nonstandard tests.

8. Write technical papers and reports; and prepare standards and specifications for processes, facilities, products, and tests.

9. Direct, coordinate, and advise personnel in test procedures for analyzing components and physical properties of materials.

branches of chemistry

Chemistry is generally divided into two broad branches: organic
chemistry and inorganic chemistry. Other types of chemistry include physical chemistry, biochemistry, and analytical chemistry, with each field branching off into several specific subfields.

Organic Chemistry

Organic Chemistry has to do with the study of compounds that contain carbon (and sometimes hydrogen). Even though carbon is only the fourteenth most common element on the planet, it produces the greatest number of different compounds on Earth.

Inorganic Chemistry

Inorganic chemistry involves the study the properties and
reactions of compounds that do not contain carbon and which are
not organic. There are many branches of inorganic chemistry, including geochemistry,
nuclear science, coordination chemistry, and bioinorganic chemistry.

Physical Chemistry

As its name implies, physical chemistry has to do with the
physical properties of materials. Physical properties that are studied may include the electrical and magnetic behavior of materials, as well as their interaction with electromagnetic fields There are several subcategories of physical chemistry. These
include thermochemistry, electrochemistry, and chemical kinetics


Biochemistry is a branch of chemistry concerned with the
composition and changes of living matter. Biochemists commonly
focus on the physical properties and structures of biological
molecules. Common biological molecules include carbohydrates, proteins, lipids, and nucleic acids. Biochemistry is sometimes referred to as physiological chemistry and biological chemistry. Biophysics, molecular biology, and cell biology are
research fields closely related to biochemistry.

Analytical Chemistry

Unlike the other main types of chemistry, analytical chemistry
doesn’t deal specifically with specific elements. Analytical
chemistry is concerned mainly with the various techniques and
laboratory methods used to determine the composition of materials. Qualitative and quantitative analysis are the two most basic methods used in analytical chemistry. Qualitative analysis has to do with identifying all the atoms and molecules
in a sample of matter, with attention paid to trace elements. Quantitative analysis also involves determining the atomical and molecular structure of matter, but includes also measuring the exact weight of each chemical constituent.

The science called chemistry

The history of chemistry may be said to begin with the distinction of chemistry from alchemy by Robert Boyle in his work The Sceptical Chymist (1661). Both alchemy and chemistry are concerned with the nature of matter and its transformations but, in contrast with alchemists, chemists apply the scientific method. The history of chemistry is intertwined with the history of thermodynamics, especially through the work of Willard Gibbs.


a. The science of the composition, structure, properties, and reactions of matter, especially of atomic and molecular systems.

b. The composition, structure, properties, and reactions of a substance.

c. The elements of a complex entity and their dynamic interrelation: "Now that they had a leader, a restless chemistry possessed the group" (John Updike).

SCHOOL YEAR 2007 - 2008

welcome students this is the start of a new year for learning chemistry, whose ancient origin has been the use of magic in science
have fun exploring my page