chemistry

closing

2009-06-28T13:00:00.000-07:00

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acids and bases

2007-08-05T00:01:00.001-07:00

Acids are compounds that tend to give up a hydrogen ion (H+). They are usually sour. They react with bases to form salt and water.

Bases are compounds that tend to receive a hydrogen ion (H+). They are usually bitter. They react with acids to form salt and water.

Indicators are compounds that slightly change their structure, and also their color, in the presence of acid or base.

Neutralization reaction is the reaction between an acid and a base, forming a salt and water.
There are numerous acids and bases in our household: vinegar, muriatic acid, car battery acid, lye, baking soda, spirit of ammonia

Acids in the atmosphere are usually produced by nitrogen oxides and sulfur oxides that are released into the atmosphere from the burning of fossil fuels. They may be carried to the ground by rain.

the mole concept

2007-08-04T23:59:00.000-07:00

A mole contains the same number of particles (atoms, molecules, ions). It is a specific number of chemical units.
A mole is a quantity of substance that contains Avogadro’s number of units or particles, which is equal to 6.02 x 1023.
Molar Mass (MM) is the mass in gram of one mole of a substance.
For elements, it is numerically equal to the atomic mass, and for compounds, it is numerically equal to the molecular or formula mass.
The amount of substance can be expressed in three ways:
Mass
Moles
Number of particles

factors affecting solubility

2007-08-04T23:57:00.000-07:00

1. Effect of Temperature
For some substances to dissolve in a given solvent, heat is absorbed. The reaction is endothermic. In this case, an increase in temperature increases solubility. For some substances, heat is released when they dissolve in a given solvent. The reaction is called exothermic. In this case, an increase in temperature decreases solubility.

Generally, an increase in temperature in the solubility of solids in liquids increases solubility. But for solubility of gas in liquids, an increase in temperature decreases solubility because gas evaporates as temperature increases. .

2. Effect of Pressure
Pressure unlike temperature has little effect on solutions unless the solute is a gas. An increase in pressure causes greater interaction between particles of the gas and the liquid, thus, increasing solubility.

3. Nature of solute and solvent
Nature of both the solute and the solvent affect the solubility.

Substances with similar intermolecular attractive forces tend to be soluble in one another. This generalization is stated as "like dissolves like."
Non polar solutes are soluble in non polar solvents; Polar or ionic solutes are soluble in polar solvents
Liquids that are attracted by charged objects are composed of polar molecules; those that are not attracted by a charged body are non polar

solubility

2007-08-04T23:55:00.000-07:00

Solubility refers to the amount of solute that can dissolve in a given solvent at room temperature.

How do substances dissolve? Solvation - there is an interaction between the solute and the solvent. The solute particles are usually surrounded by the solvent particles. This process is called solvation.

The nature of the solute and the solvent affects whether a substance will dissolve. If the solute contains charged particles, it will also dissolve in a solvent that has a tendency to have charges. On the other hand, a solute that does not have a tendency to be charged can only dissolve in a solvent that has similar characteristics.

Agitation makes the solute dissolves more rapidly because it brings fresh solvent into contact with the surface of the solute. However, agitation affects only the rate at which a solute dissolves. It cannot influence the amount of solute that dissolves. An insoluble substance will remain undissolved no matter how much the system is agitated.

Rules on solubility:
1. A substance is insoluble if less than or equal to 0.1g dissolves in 1 liter of water at room temperature.

2. A substance is slightly soluble if greater than 0.1g but less than 10 g dissolves in 1 liter of water at room temperature.

3. A substance is soluble if 10 g greater than 10 g of the substance dissolves in 1 liter of water at room temperature.

saturated, unsaturated and supersaturated

2007-08-04T23:54:00.000-07:00

Solubility is defined as the maximum amount of solute dissolved by a given amount of solvent at a definite temperature.

The solubility of the given substances in a given solute is temperature-dependent.

Solution containing the maximum amount of solute at room temperature is saturated. When more solute is added into the solution the solute will no longer dissolve.

If the solution contains the maximum amount of solute at an elevated temperature the solution is supersaturated. When more solute is added into the solution, crystals will form.

If the solution contains less quantity of solute than what can be dissolved at room temperature it is unsaturated. When more solute is added into solution the solute dissolves.

how dissolving process happens

2007-08-04T23:53:00.000-07:00

The solute and solvent interact to form a homogeneous mixture.

Since it is a homogeneous mixture, it means that the particles of solute and solvent are intimately mixed, so that they cannot easily be identified from each other in the mixture (one phase, one consistency, one texture).

The solvent particles surround the solute particles in the dissolving process.
The solvent and solute particles interact with each other. They have similar polarity. From this comes the saying that “like dissolves like”: Molecules with like polarity dissolve in each other.

If the solvent and solute particles are not similar in polarity, there will be no interaction (oil and water), and the solvent particles cannot surround the solute particles. In this case, they would form a heterogeneous mixture.

types of solution

2007-08-04T23:51:00.000-07:00

Gases dissolve in other gases, as we experience in air. Nitrogen, which is about 80% of the mixture, is considered the solvent. Here we have a gaseous solution.

Gases like oxygen and carbon dioxide are soluble in water. We experience this in carbonated drinks and sparkling wine (champagne). We have a liquid solution, but the solute is a gas.

Liquids like alcohol and acetone are soluble in water. Beer, rubbing alcohol, and other natural juices are examples of this. We also have a liquid solution here.

Solids like salt, baking soda, and sugar are common solutes in water.

Three types of solutions based ion its final state are solid solution, liquid solution and. gaseous solution.

Aqueous solution is a solution where the solvent is water. Alcohol or any other organic solvent can also be used as a solvent and the solution is called an organic solution.

components of a solution

2007-08-04T23:50:00.001-07:00

A solution is a homogeneous mixture of particles (ions, atoms, or molecules). Since it is homogeneous the component parts cannot be easily identified.

It is made up of the solute, which is present in lesser amount and the solvent, which is present in greater amount. The solute is the dissolved medium while the solvent is the dissolving medium of the solution.

Water is not a universal solvent. If it were, it should dissolve solutes and if it is a universal solvent, it should dissolve everything. But clearly it does not do that. Otherwise fish and other aquatic life would all be dissolved in the ocean; we would dissolve in the water of our cells. It might be a common solvent, because it dissolves many things, but there are just as many things it does not dissolve like metals, rocks, plastics, glass, fats, cellulose, many proteins. Organic solvents like alcohol or gasoline can also have a long list of substances that they can dissolve.

element and compound

2007-08-04T23:48:00.002-07:00

An element cannot be broken down any further.

A compound can be broken down into its constituent elements. It is made up of two or more kinds of atoms.

Organic and inorganic compounds

2007-08-04T23:48:00.001-07:00

Organic substances are compounds that contain the element carbon attached to itself and hydrogen.

Inorganic substances are elements and the compounds of all elements other than carbon.

identification of chemical system

2007-08-04T23:43:00.000-07:00

Homogeneous systems are one-phase systems; all parts of the systems show the same characteristics all throughout.

A heterogeneous system is a one ore more phase system; the parts retain their original properties.

A substance is made of only one kind of molecule; a mixture is made of 2 or more kinds of molecules.

solutions, (ex. salt solution), not filterable, smallest particle size, no Tyndall effect

colloids, (ex. starch & water), slight filterability particle are bigger than that of solutions but smaller than suspensions, Tyndall effect was observed

suspensions, (ex. starch & water), very filterable, biggest particle size, Particles settle at the bottom, No Tyndall Effect

conversion

2007-08-04T23:37:00.000-07:00

Metric System
1000 m = 1 km
1 inch = 2.54 cm
1 m = 100 cm
1 gallon = 3.785 L
1 m = 1000 mm
101.325 Pa = 1 atm
1 L = 1000 mL
1 foot = 12 inches
1000 g = 1 kg
1 mile = 5280 ft

Metric System
60 s = 1 hr
24 hrs = 1 day
365 days = 1 year
100 yr = 1 century
1 atm = 760 mmHg

Dimensional analysis:
The technique of converting between units is called dimensional analysis.

Conversion factors: Conversion factors are the ratios of equivalent measurements. It can also be used when converting from English to Metric and vice-versa. In a conversion factor, the numerators on both sides of the equation are equal.
Ex. = = 1
or = = 1
How do you know which unit of a conversion factor must be in the denominator? The unwanted units are placed at the bottom so that they will be cancelled out; the desired unit is on top so that it would be retained.
Ex. Convert 5.6 dm (decimeter) to meters.
The problem is: ? m = 5. 6 dm

By definition, 10 dm = 1 m
Therefore we write,
(5.6 dm) (1 m) /(10 dm) = 0.56 m

Significant Figure Rules

2007-07-30T18:45:00.000-07:00

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

2007-07-30T18:40:00.000-07:00

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.

Clothing

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

2007-07-30T18:38:00.000-07:00

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

2007-07-30T18:32:00.000-07:00

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

2007-07-30T18:27:00.000-07:00

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

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

2007-07-30T18:19:00.000-07:00

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.

Chemistry

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

2007-07-30T18:12:00.000-07:00

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

Electronic Configuration

2006-11-21T21:14:00.000-08:00

Learning Outcome:At the end of the sessions, you must be able to draw or make the electronic configuration of any given element

Learning Presentation:

It is important to know how to draw the electronic configuration of elements because it is a way to know the properties of element. click here to know how.

Another great way to memorize the mnemonics for electronic configuration is the following rhyme :

Si Sally Pumasok Sa Pinto Si Daddy Pumasok Sa Dilim Paano Si Franky Daddy Paano Si Franky Daddy Franky Daddy Franky (Each letter corresponds to the shape fill it in with the principal quantum number start numbering S with 1, P with 2, D with 3, and F with 4)

Atomic Emmission Spectra

2006-11-08T16:58:00.000-08:00

Learning Outcome:At the end of the sessions, you must be able to explain how the emission spectra of elements provide for the existence of the energy level

Learning Presentation:

Colors add beauty to life and all the things around us. But what is color and how do see color? Visible light waves are the only electromagnetic waves we can see. We see these waves as the colors of the rainbow. Each color has a different wavelength. Red has the longest wavelength and violet has the shortest wavelength. When all the waves are seen together, they make white light. Direct evidence of this is the rainbow.

Visible Light color is can be separated by lenght of wavwlenght. click here to find out

Elements give out specific color of light when their electrons are exited and promoted to the next energy level (we will discuss this later) this wavelenght helps in the identification of elements that are present in other planets or stars like how helium is discovered in the sun.

TO identify elements present chemist perform a flame test. (Atomic emmssion spectra flame test click here (this requires window media player)

Isotopes

2006-10-24T22:12:00.000-07:00

Lesson Title: Isotopes

Learning Outcome:At the end of the sessions, you must be able to define isotopes, cite the relationship between atomic mass and the relative abundance of isotope identify the use of some radioactive elements/isotopes

Learning Presentation:

What is an isotope? click here to find out you can also check you text books its on page 64-65 :)

or play this video for better understanding

From our previous lessons the atomic mass is the number of protons plus the number of neutrons but why are the mass in the periodic table of elements not in whole number is it because of the electrons?

The answer is no, it is not in whole numbers because it is the average mass of the isotopes present of that element to know how to calculate click here

Generalization:
1. The protons and neutrons are particles of the nucleus. The American physicist A. J. Dempster and the English chemist F. W. Anston (1914) found out that some elements have atoms with different atomic masses. These are called isotopes of the element. Atoms of the same element would have the same atomic number. The atomic mass of isotopes varies because they have different numbers of neutrons. Atomic mass is given by the sum of the masses of p+ and no present in the atom. Mass number is rounded off for convenience

1. The variation in the number of neutrons does not change the identity and therefore, the properties of an element. It is atomic number or the number of protons that identifies an element.

2. Atomic mass is generally, not a whole number. It is the weighted average of the masses of isotopes of a particular element. The percentage of isotopes of a particular element. The percentage abundance of each isotope is taken into account.

3. Isotopes are classified as stable and unstable.
a. Stable isotopes do not exhibit radioactivity, which explains why they exist and persist in nature. Many elements that occur naturally and abundantly on earth are stable isotopes. 16O and 12C are examples.

b. Unstable isotopes exhibit radioactivity (tremendous emission of invisible rays due to the splitting of the nucleus of an atom) and thus, are known as radioisotopes.

4. Using the unstable isotopes/radioisotopes
a. Dating fossils and rocks - Geologists use radioactive decay rates to tell the ages of rocks and fossils. Uranium –238 is used to determine the age of rocks. It takes 4.5 x 109 years for half of the sample of U-238 to decay.

b. Radiocarbon dating - This method is used to determine the ages of materials, which were once living. It is based on the decay rate of carbon-14. Living organisms contain an almost fixed amount of carbon-14 per unit mass. When the organisms die, C-14 starts to decay according to the rate law. The half-life of C-14 is 5730 years.

c. Medical uses - Radioisotopes are used to detect and treat abnormalities in the body.

Activity: click here to practice on a game

Application/ Valuing Assignment:
Answer the following by posting your answer or write on a piece of paper you will be graded based on the following
1. Give 2 or 3 examples of elements with isotopes which isotope is beneficial and how and which are not beneficial and why?
2. What is the impact of isotopes to our lives?
3. What are the biological effects of radiation?
4. What is the difference between natural and artificial radioactivity?
5. Can both be utilized to be beneficial to man?

atomic structure

2006-10-16T17:55:00.000-07:00

Lesson Title: Sub-atomic particles

Learning Outcome:

At the end of this your should be able to know the different sub-atomic particles of an atom, what is an isotope and compute for the number of sub-atomic particles provided with a given.

Presentation:
As i have discussed earlier the atom was the smallest indivisible unit of matter it, this was first coined by democritus, and refined by Dalton. But the discovery of Thomson, Rutherford, Chadwick, and Goldstein has made us think otherwise. The atom is no longer a solid sphere but it is made up of several componets the protons, neutrons and electrons.

To learn more about this sub-particles click here.

Computing for the number of protons, electrons and neutrons as well as the atomic number and mass can be a daunting task, but follow this link and you will understand better.

Test your understanding click here

Sometimes elements vary in mass number they are called isotopes

Assignment
How will you know the identity of the atom?
Is it possible for an atom of the different element to have the same number of electron and neutron? click here to answer or submit in 1 whole paper unique answer is required you will be graded as the following

Rutherford’s Experiment

2006-09-20T21:43:00.000-07:00

Lesson Title: Rutherford’s Experiment

Learning Outcome:
At the end of the sessions, you must be able to explain Rutherford’s experiment to prove the existence of the nucleus.

Learning Presentation:
Rutherford as you might remember contributed to the idea of what an atom might have looked like click here to find out how he did it

If you want additional references to help you know him better check out your textbook its on pages 61 and 62. :)

In 1899, J. J. Thomson proposed a model of the atom. The atom according to him is a positive ball of electricity wherein negatively charged particles are embedded. For this time, this so-called plum pudding model was accepted.

In 1908-1909, Ernest Rutherford and his co-workers performed the well-known gold foil experiment. They hammered a gold foil into a thin sheet that was a few atoms thick. They fired alpha particles at the thin gold foil. An alpha particle is positively charged (charged 2+) with a mass four times (mass 4 u) that of a H-atom.

Rutherford tested Thomson’s model of an atom. H e concluded that if his model were correct, most of the alpha particles would pass through a thin gold foil with very slight deflections, because the positive charge of the atom was diffused.

play this video to have a clearer and better understanding of the atom as proposed by Rutherford

Rutherford was surprised by the result of his experiments. His observations were the following:
Most of the alpha particles passed through the gold foil undeflected.

A few alpha particles passed through the gold foil with large angles of deflection.
Still fewer alpha particles bounced back in the direction from which they came.

The bouncing back and scattering of the alpha particles could not be satisfactorily explained using Thomson’s model of the atom.

After several years of study, Rutherford interpreted his observations. His conclusions were:
The atom has a central core called the nucleus. It is here where the mass of the atom is concentrated.

The charge of the nucleus is positive.

The nucleus is very small compared to the volume of the atom. The atom is mostly empty space.

The electrons are found outside the nucleus.

Later measurements showed that diameter of a nucleus are very small (about 10-12 cm) compared to the diameter of an atom (1 to 5 x 10-8 cm). This is about the size of a marble compared to the size of a softball field (atom).

Activity:
To measure if you have gained sufficient knowledge about the atom try this activity
Atomic Hangman

Assignment:
How did he discovered the nucleus? how did the deflection of the alpha particles led him to say that there is a nucleus? Place your answer by clicking here

Evaluation:
A score of more than 70% is excellent and an indicator that you are ready for your next lesson
Take this quiz and test your knowledge

Cathode Rays and the Electron

2006-09-20T21:40:00.000-07:00

Lesson Title: Cathode Rays and the Electron

Learning Outcome:
At the end of the sessions, you must be able to:
1. Discuss what cathode ray and radioactivity reveal about the atom.

Learning Presentation:
An atom is so small and yet it still have sub particles, how can you discover something so small that it has never been seen????????????

How did his experiment lead him to discovery this unseen particles

What did he discovered? click here

If you want to use your check another reference and get to know this person and his discovery better, check out your textbook its on pages 59 and 60.

Generalization:
1. Much of our understanding of the structure of the atom came from the study of electric charges in rarified gases. William Crookes (1832-1919), an English chemist, using a special vacuum discharge tube later called Crookes’ tube, show that there was some kind of matter coming from the cathode (negative electrode).

2. These particles were called cathode rays because they originated from the cathode. Numerous experiments made by Julius Plucker, Johann Hittarf, William Crookes, and others showed that cathode rays exhibited the following properties:
a. Cathode rays are emitted from the cathode when electric current is passed through an evacuated tube containing a gas at very low pressure.
b. The rays travel in a straight line as indicated by the shadow cast by small objects placed along its path. Metal objects struck by the rays become red hot.
c. The cathode rays upon striking a zinc sulfide (fluorescent) screen, cause it to emit random flashes of light.
d. The cathode rays have a negative charge. This is shown by the fact that they are attracted toward positively charged metal plates held outside the tube.

3. Joseph John Thomson (1856-1940), an English physicist, after a series of investigations, established the particle nature of cathode rays.He determined the velocity these particles and the ratio of electric charge (e) to mass (m), e/m.

4. The value is about –1.759 x 108 coulombs/gram. He further concluded that cathode rays are negatively charged and are fundamental particles of matter. Later they were called electrons.

5. Thomson helped revolutionize the knowledge of atomic structure by his discovery of the electrons.

Assignment:
What is this sub particle?and what is its importance to our lives today? post your answer in my amazing forum by clicking here

Evaluation:
To test if you have gained sufficient knowledge
test yourself click here a score of more than 70% is considered sufficient
good luck :)

Dalton's Atomic Theory

2006-09-20T21:11:00.000-07:00

Lesson Title: Dalton’s Atomic Theory

Learning Outcome:
At the end of the sessions, you must be able to:
1. Enumerate and explain the four assumptions made by John Dalton.
2. Explain the laws of chemical changes in terms of Dalton’s Atomic Theory.

Learning Presentation:
You have meet John Dalton previously, and as you have known he is the forerunner of today’s atomic theory, let us look closely his contributions click here

Another great references to have a full understanding of the contributions he made to the atomic theory is your textbook its on page 57 ;)

Generalization:
The four assumptions of John Dalton in his “Atomic Theory of Matter:
1. Each element is composed of tiny particles called atoms.

2. All atoms of a given element are identical; atoms of different elements are different and have different properties (e.g. masses).

3. Atoms of an element are not changed into different types of atoms by chemical reactions; atoms are neither created not destroyed in chemical reactions.

4. Compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kind of atoms.

Assignment:
What do you think is the most important contribution of Dalton in the atomic theory formulation, is his theory still applicable today? How?
Send your answer by clicking here

Evaluation:
Click here to evaluate yourself, a score of more than 70% means excellent understanding of the lesson

models of the atom

2006-09-20T20:29:00.000-07:00

Lesson Title: Models of the Atom

Learning Outcome:
At the end of the sessions, you must be able to:
1. Know the different models of the atom

Learning Presentation:
Earlier I have let you imagine what is an atom, in this lesson we will see each of the different models as contributed by each of the scientist we have discuss earlier

JJ. Thomson Proposed a model of the atom click here to know more about it

Another scientist also studied the structure of the atom but it was more of an accidental discovery type he tried to verify the earlier atomic model but it resulted to a change in the idea of the structure of the atom click on the lick below to know more
Rutherford model of the atom click here to know more about it

Now from this model another scientist perfected the model of the atom and stipulated another atomic model, do you want to know what he found out? click below
Bohr Model click here to know more about it

To better grasp at the idea of the atom from its humble beginnings and to its present form today click on the link below
If you want to see the summary of the atomic model click here

Atomic models are also found in your textbook read it to have a fuller and better understanding of the model its on page 76 -77 :)

Assignment:
Did it match your initial idea of an atom? how?
visit my forum for this discussion click here

Activities:
To test your knowledge try this game click here

Evaluation:
Test your ability by clicking here, a score of more than 70% means excellent

Development of the Atomic Theory

2006-09-20T19:42:00.002-07:00

Lesson Title: Contributions of early Scientiest in the development of the Atomic Theory

Learning Outcome:
At the end of the sessions, you must be able to:
1. Trace the beginning of the development of the atomic theory.
2. Identify and recognize the significance of the contributions of early scientists in the development of atomic theory.

Learning Presentation
The atom is the most basic building block of matter, and chemistry is defined as the study of matter. Therefore to fully understand chemistry we must take a look at the atom.
What is an atom and what does it looks like?
I want you to imagine an atom and we will compare it later if your idea fits with the existing model of an atom.

Atoms though it may seem as a current idea was developed long ago. By Leucippus of Miletus and his student Democritus of Abdera.

Leucippus and Democritus: How did the two philosophers characterize the smallest unit of matter? What does the Greek word atomos mean?

Click on here to know how they came up with the idea of atoms

Another scientist gave evidence to support Democritus idea about atoms?
click here

John Dalton (1766-1844), an English chemist, integrated the results of the work of Boyle, Lavoisier and Proust and used them to provide the theory about the atomic nature of all matter. He was credited for the atomic theory. Why was the credit for atomic theory not given to Leucippus and Democritus when they were the first people to express the idea?

How significant were the studies of Boyle, Lavoisier and Proust in the development of atomic theory?

Generalization:
1. The idea of atoms as the smallest particle of matter started with Leucippus and Democritus about 400 BC.

2. In his study on gases, Robert Boyle (1627-1691) explained compressibility of air in terms of tiny particles forced closer together.

3. The Law of Conservation of Mass proposed by Antoine Lavoisier (1743-179) could be explained by atoms being indivisible. In chemical reactions, atoms only separate and/or unite with other atoms. No atoms can be destroyed nor created; thus, no change in weight of products is expected.

4. The Law of Definite Proportions or the Law of Definite Composition proposed by Joseph Louis Proust (1754-1826) could be explained using the idea of atoms. A compound is formed by the union of definite number ratio of combining atoms.

5. The Law of Multiple Proportions was put forward by John Dalton.

6. The three laws served to support the atomic theory proposed by Dalton in 1804. Without the work of these three scientists, Democritus idea of atoms could not have turned into a theory.

Assignment:
Visit my furom and give me a summary of the scientist that contributed to the atomic theory, also include the significance of wach discovery plus a summary of who do you think contributed the most to the atomic theory and why? click here to post answer

Evaluation:
Test your skill by clicking here, a score of more than of 70% is considered excellent

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