BIOCHEMICAL EVOLUTION

Origins of Life: Biochemical Evolution
Fossilized bacteria inform the scientists the story of how life
may have evolved in the unique environment of primordial
Earth 3.8 billion years ago. Let us find out how life started....
How life evolved?
Now picture this, imagine swimming in a cosy volcanic vent
of searing heat. Ammonia and methane swirl like a cosmic
bowl of soup. Steam rises from the water into the thick
chemical atmosphere. Suddenly, a bolt of lightning strikes
the sky. The ammonia and methane combine just at the
water's surface and is fed by the heat from below. At that
moment something new appears: an amino acid; a protein;
which is a building block for life itself. According to scientific
convention, that's how it happened over 3.8 billion years ago
here on Earth.
Ever since Darwin sailed to the Galapagos and wrote his first
theories of evolution, scientists have been trying to find the
origins of life. Humans have been trying to find this very
thing long before Darwin ever hypothesized that human
beings evolved- as all animals did from organic compounds.
But in recent years more evidence has been found through
evolving technology and research. Science and mankind have
been provided with some new answers about an old problem.
If we did evolve from simple compounds in a complex
environment, then how did it happen?
Scientists currently believe that planet Earth formed around
4.5 billion years ago after the "Big Bang" created our
universe. Then, sometime around 3.8 billion years ago, the
first rock formations began to appear, and microorganisms
known as arch bacteria developed. Around 7 billion years in
between, life began as a result of a specific set of necessary
elements, and random chance.
Beginnings of Biochemical Evolution
We know that the so-called "primordial soup" of our world
was made up of lots of water on the surface, and great
quantities of methane and ammonia in the atmosphere.
Below the surface of the water, volcanoes were continuously
erupting and underwater land masses were being created.
These land masses eventually rose to the "surface".
The volcanoes were also creating a lot of heat and steam. A
great storm of chemical activity in the skies of that
primordial Earth was also getting added to the heat and
steam mixture. The movements of Earth, sky, and chemicals
resulted in electrical storms. Based on recent studies in
microbiology, biochemistry, and chemical palaeontology,
scientists believe that either electrical activity or a catalytic
metallic ion was created which led to the creation of amino
acids.
Amino acids are the simplest forms of an organic compound.
They are also proteins. DNA and RNA derive from the
successful building of protein. Once DNA and RNA begin to
build upon themselves, complex organic materials are
created including living cells such as bacteria, and amoebas.
By 3.5 billion years ago cyan bacteria had developed.
Around 2.2 billion years ago, photosynthetic bacteria had
utilized enough chlorophyll and emitted "waste" to create an
oxygen rich atmosphere. It was approximately 2 billion years
ago when bacteria developed into eukaryotes which were
regarded as the first complex living cells. Many of the
ancient water-bearing bacterium can still be seen today in the
fossilized mounds called as stromatolites along different
beaches around the world. These stromatolites are serving
as a great evidence that scientists are using to investigate
the era of the primordial soup. At first, scientists did not
realize that these mounds were in fact fossilized bacteria.
The Contribution of Bacteria
Bacteria are found in all shapes, sizes, and conditions.
Bacteria can thrive in just about any environmental condition
right from extreme heat to extreme cold. As a result,
scientists have been exploring the Arctic and Antarctica to
find clues to Earth's bacterial past. Bacteria fossils as well
as young living bacteria have been found hidden in these
harsh places. Scientists have also found bacterial fossils in
salt beds that are hidden elow the Earth's surface.
With the sedimentary layering of Earth over time, crystals are
formed when moisture is trapped. Scientists found ancient
Bacillum bacteria in salt crystals that were found in the New
Mexico desert. The samples were revived and new spores
were produced after millions of years of imposed hibernation
in salt crystal. The estimate for this particular sample is 256
million years old. The discovery takes us one step closer to
the study of the elements and events that spawned life on
our world 4 billion years ago.
In the end, we may never know what exactly happened in
that ammonia and methane filled world of chemical storms
and volcanic heat. But with each day of new inventions,
technological advances in biochemistry, we will learn more:
more about our world; and ourselves.

GET RID OF PIMPLES OVERNIGHT(Home Remedies to RemovePimples)

1.) Lemon Juice to Get Rid of Pimples
Overnight
A couple of drops of lemon juice work well,
when applied on a pimple. Despite the fact
that it causes a touch of tingling, it helps to
reduce inflammation and swelling.
Ensure you apply just fresh lemon juice and
not packaged items.

Sip a clean swab of cotton in the juice and
apply on the pimples before you go to bed.
Another remedy is to make a paste by
mixing a teaspoon of cinnamon powder with
a tablespoon of lemon juice.
Apply the paste on the pimples and leave
the paste overnight and wash off in the
morning with warm water.
We would not recommend this remedy for
individuals with sensitive skin since It may
cause irritation, dryness and redness.
2.) Get Rid of Pimples with Washing Your Face
Each Night
Salt-water is very effective in removing oils from
the face and mitigating pimples. If you wash off
the oil every night before going to bed, the next
morning the pimples will start losing its
prominence or removed overnight.
3.) Get Rid of Pimples Overnight with
Toothpaste
Toothpaste is an extraordinary treatment to get
rid of pimples. Also, it is available to most of
individuals without needing to take an outing to
the supermarket. Toothpaste is best utilized as
a catch up to icing to create the quickest
comes about. It is essential to note that white
glue must be utilized instead of gel toothpaste
to get rid of pimples.
Apply some white toothpaste to the
influenced ranges of the skin before quaint
little inn overnight, washing with cool water
in the morning to get rid of pimples.
In the event that you aren’t going anyplace,
you can rehash the procedure amid the day,
making a point to leave the toothpaste in
contact with the pimples for no less than
thirty minutes to be viable.
4.) Get Rid of Pimples Overnight with
Cinnamon-Honey Mixture
In the event that you are eager to reduce your
acne inside a solitary night you better strive for
this remedy.
First of all make a paste of cinnamon
alongside honey.
Then cleanse your face before applying the
paste on the pimples.
Have a peaceful and average sleep.
See the difference in the wake of washing
your face following day in the morning.
5.) Get Rid of Pimples with Garlic
Garlic has anti-bacterial properties that
assistance to battle acne. Nonetheless, never
apply the garlic without weakening it first.
Take fresh garlic and after grinding extract
the juice from it.
Dilute the garlic by adding a few drops of
water into it.
Alternatively, you can mash 2-3 garlic cloves
in water. Let it soak in water for say 10-15
minutes.
After that add some aloe vera gel into it.
Apply it on the affected area to get rid of
pimples.
You can likewise have garlic to get rid of
pimple breakouts later on.
6.) Egg Whites to Get Rid of Pimples Overnight
The protein rich egg whites may save your day
in case you apply it before going to bed. Take
an egg and separate the yolk by moving it back
and forth between the two halves of the shell.
The whites will be collected in the bowl and the
yolk will stay back in the shell half. Apply the
egg whites on the pimples using your fingers.
Leave it to dry and stay overnight. Wash your
face with warm water in the morning to get
pimples-free face.
7.) Use the Sandalwood Paste with Rose Water
Get Rid of Pimples Overnight
Make the paste by rubbing sandalwood stick
with rose water on a rough surface and apply on
your pimples before sleeping. Leave it overnight
and wash with cold water in the morning. In
case your skin becomes excessively dry the
next morning, use the paste only for limited
hours on your face or add some milk while
preparing the paste. Milk will help remove the
dryness.
8.)Apple Cider Vinegar to Get Rid of Pimples
Naturally
Take a cotton ball and dip it in the apple cider
vinegar. Apply it on the pimples and keep it
overnight. You may feel extremely happy with
its effectiveness the next morning.
9.) Apply a Paste of Salt and Olive Oil to Get
Rid of Pimples Overnight
Make a paste of salt and olive oil and use it on
the affected area. Wash it off after some time.
Before you go to bed, apply a cold pack or an
ice pack on your face. This will help reduce the
swelling in your face and redness in the
pimples.
10.) Use Calamine Lotion to Get Rid of Pimples
Overnight
Cleansing must be carried out consistently
without fizzle before going to sleep or else your
skin won’t have the capacity to breathe.
Clean up your entire face or just the
affected area with the assistance of an
astringent.
You need to apply calamine lotion over the
affected part.
Have a peaceful and sound sleep at night.
After wake-up in the morning, wash your
face with lukewarm water to get rid of
pimples.
You will unquestionably be cheerful and
eager to see that your pimple has reduced
from what it was the prior day.
12.) Honey to Get Rid of Pimples Overnight
Honey makes a phenomenal results to get rid of
pimples.
To see its magical effect, you need to apply
some honey over your pimples.
Allow it to dry all alone for 60 minutes, you
can leave it for overnight also.
Then rinse it off with ordinary water.
Say farewell to zits with the magical effect
of honey.
Honey being a common anti-biotic, it murders
the bacteria that cause pimples. Honey also
keeps the skin healthy with the help of its
hydrating properties.
13.) Steam to Get Rid of Pimples Overnight
Steaming is magnificent for your skin and will
become more effective, in case you have
pimples. Steaming will help your skin breathe by
opening your skin pores. This helps dispose of
oils, dirt and bacteria trapped in the pores that
can cause infection or inflammation.
Fill a substantial compartment with boiling
point water and allow the steam to interact
with your face for a couple of minutes to get
rid of pimples.
Rinse your face with lukewarm water and, in
the wake of drying, apply a without oil
moisturizer.
This treatment will likewise give your
appearance a dazzling sparkle.
14.) Peppermint to Get Rid of Pimples
Overnight
Peppermint is a powerful herb that can help to
get rid of pimples fast. The cooling, soothing
effect of the menthol display in peppermint
helps reduce the irritation and redness caused
by pimples. Peppermint have antiviral and
antibacterial properties likewise help eliminate
bacteria that cause pimples.
Crush some peppermint leaves to extract the
juice.
Apply the juice gently on your pimples and
leave it for 10 minutes.
Wash your skin with cold water to get rid of
pimples.
In the event that fresh peppermint leaves are
not accessible, you can utilize peppermint oil,
which contains various vitamins and vital
unsaturated fats. Take two to three drops of
peppermint oil and apply it on your pimples. Rub
the oil for a couple of minutes and afterward
rinse with water.
15.) Cucumber to Get Rid of Pimples Overnight
Cucumber is a rich wellspring of potassium and
vitamins, for example, vitamin E, vitamin A and
vitamin C. It also has a cooling and soothing
effect on the skin.
Cut one or two fresh cucumbers into pieces
and soak them in water for 60 minutes. The
supplements, for example, vitamin A,
potassium and chlorophyll will exchange to
the water.
Strain the water and beverage it, or utilize
the water to wash your face.
You can likewise make a face mask by grinding
one cool cucumber. After grinding, make a mask
on your face and allow it to dry for 15 to 20
minutes. After getting dry, wash your face with
the lukewarm water. This will help in cleaning
bacteria and dirt from your pores.
16.) Ice to Get Rid of Pimples Overnight
Momentary relief from pimples can be gotten
from ice.
First, take an ice 3d shape and wrap it up in
a delicate and clean bit of material.
Now, apply everything over your pimple and
leave for a few minutes.
You can likewise take an aluminum foil and
fold ice cubes in it. Verify that the ice
doesn’t drop out from the foil.
Now put the foil stuffed ice cubes in a Ziploc
pack.
Check whether any air is trapped inside the
zip lock pocket. Apply it directly on the
pimples for faster relief and a soothing
effect.
17.) Basil Leaves to Get Rid of Pimples
Overnight
Liquid extracted from basil leaves is an
alternate effective weapon for battling pimples.
Take few basil leaves and dip them in warm
water for around 20 minutes.
Before going to bed, cleanse your face and
apply the extracted liquid with the
assistance of a cotton ball to get rid of
pimples overnight.
Let it stay on the affected area for the
entire night with the goal that it can dry
consequently.
Rinse it off in the morning and see the
difference in your skin.
The pimples have reduced and you will get the
clear skin. Using basil leaves is the best option
to get rid of pimples overnight.
18.) Orange Peel and Juice to Get Rid of
Pimples Overnight
As indicated by Cosmetic Dermatologist
Principles and Practice expresses that the
causticity and vitamin C substance in oranges
makes it a flawless cure for acnes.
First wash your hands before touching your
skin, since dirty hands can acquaint bacteria
with the skin.
Then wash your face with warm water as
this helps to enlarge the pores.
Gently rub the orange peel on the affected
area.
You ought to utilize separate orange peels
for every pimple, generally, there is a high
risk of bacterial infection.
Now dip a cotton ball or swab in orange juice
and apply it on the acne.
Change the cotton ball while treating acne
to prevent bacteria from spreading.
Now wash your face with cold water, this will
choke the pores and prevent from further
obstructing of pores.
19.) Papaya to Get Rid of Pimples Overnight
Papaya helps to remove dead skin cells and
additional layer of oil from the skin. The papaya
will help to reduce the inflammation and
prevents pus with the helps of its catalyst called
Papain.
Rinse your face with water and pat dry.
Then mash a papaya to a consistency with
the goal that it can be effectively applied to
the skin.
Apply and leave it for 15-20 minutes and
after that wash it off.
If your skin gets dry in the wake of washing
just apply a moisturizer to hydrate it.
20.) Banana Peel to Get Rid of Pimples
Overnight
Like bananas are useful for skin, the peels are
additionally effective to remove pimples. The
peel has lutein, which is a powerful antioxidant
that helps to reduce inflammation and allows
healthy cell development.
Peel the banana; now rub the peel on your
face in a roundabout movement to get relief
from the redness and uneasiness caused by
acne.
When you have secured your face entirely
with the peel, wait for minimum 25 to 30
minutes to get it dry and thereafter wash it
off.
21.) Aloe Vera to Get Rid of Pimples Overnight
Aloe Vera gel can be utilized directly on the
affected area to get rid of pimples. Aloe Vera
has anti-inflammatory and anti-bacterial
properties and helps to reduce redness and skin
irritation. Utilize enough aloe vera gel to mask
the pimples while doing spot treatment.
Better to use a fresh aloe vera leaf.
Squeeze the juice out from the aloe vera.
Now, apply this gel directly on the pimples
and leave it overnight to remove pimples.
You have to keep on repeating this process
on daily basis till the time pimples get
completely disappeared.
22.) Aspirin to Get Rid of Pimples Overnight
Curious however effective! I have discovered
this really valuable pimple fix. It works fast and
makes a clean showing of containing emissions.
Crush an aspirin tablet and add a couple of
drops of water to make a paste of it, mix
well to structure a paste and apply to the
pimple.
Let the paste dry. Aspirin is an anti-
inflammatory operator, and helps reduce the
swelling because of amassed pus.
Leave the paste overnight and wash off in
the morning. The pimple is less noticeable
after its aspirin treatment.
23.) Baking Soda to Get Rid of Pimples
Overnight
Baking Soda, ruler of home remedies works like
a surprise to get rid of pimples too. This is a
quick fix, we recommend to everybody since it
works well for sensitive skin too, dissimilar to
different remedies that cause sketchiness or
dryness.
Make a paste by mixing a few drops of
water to the baking soda.
After making the paste, apply this paste to
get rid of pimples.
Leave the paste to get it dry. After drying,
wash off with warm water and catch up with
a moisturizer.
Do not leave the paste on for more than a
couple of minutes as it could cause skin
dryness.
Other Useful Tips to Get Rid of Pimples
Overnight:
If toothpaste stings, use a mint free
toothpaste.
Take a shower after workout.
Have a balanced diet including lots of
water.

WAEC 2015 SSCE TIME TABLE

WAEC Timetable (2015 May/June Examination) – Nigeria WAEC timetable for 2015 May/June Examination (Nigeria) is out. The 2015 West African Examination Council (WAEC) Time table for the May-June Exams is available Now Below is the Complete 2015 /2016 WAEC TimeTable. West African Examination Council Nigeria Timetable; WAEC Timetable 2015 WAEC Timetable 2015/16 May/June Examination The following is the breakdown of the 2015 WAEC Time table for May/June Examination. Tuesday – 14th April, 2015 FOOD & NUT PRACTICAL — 08.30am – 9 30am _____________________________ Monday, 23rd March to Tuesday – 14th April, 2015 FOOD & NUT PRACTICAL Arabic 3(Oral) French 3(Oral) — Time will be fixed by the Council _____________________________ Friday, 27th March, 2015 Arabic 2 (Essay) — 08.30am – 10 30am Arabic 1 (Obj) —10.30am – 11.30am Friday, 27th March, 2015: Health Science 3(Alt to Practical) --- 2.00pm - 3.45pm Health Education 3(Alt to Practical) --- 2.00pm - 3.45pm _____________________________ Monday, 30th March, 2015: Home Management 2 (Essay) --- 8.30am -9.30am Home Management 1 (Obj) --- 9.30am -10.30am _____________________________ Tuesday, 31st March, 2015: History 2(Essay) --- 8.30am - 10.30am History 1(Obj) --- 10.30am - 11.30am _____________________________ Wednesday, 1st April, 2015: Data Processing 2 (Essay) --- 1.00pm – 3.00pm Data Processing 1 (Obj) --- 3.00pmm – 4.00pm _____________________________ Tuesday, 7th April, 2015 Hausa 2 (Essay — 8.30am – 10.30am Hausa 1 (Obj) — 10.30am – 11.30am Igbo 2 (Essay) — 8.30am – 10.30am Igbo 1 (Obj) — 10.30am – 11.30am Yoruba 2 (Essay) — 8.30am – 10.30am Yoruba 1 (Obj) — 10.30am – 11.30am Edo 2 (Essay) — 8.30am – 10.30am Edo 1 (Obj) — 10.30am – 11.30am Efik 2 (Essay) — 8.30am – 10.30am Efik 1 (Obj) — 10.30am – 11.30am Civic Education 2 (Essay) — 1.00pm – 3.00pm Civic Education 1 (Obj) — 3.00pm – 4.00pm _____________________________ Wednesday, 8th April, 2015: Physics 3 (Practical) (Alt A) — 8.30am – 11.15am (1st set) Physics 3 (Practical) (Alt A) — 11.40am – 2.25pm (2nd set) Physical Education 3 (Theory of Practice) --- 2pm – 4pm _____________________________ Thursday, 9th April, 2015 English Language 2 (Essay) — 8.30am – 10.30am English Language 1 (Obj) — 10.30am – 11.30am English Language 3 (Oral) — 1.00pm – 1.45pm _____________________________ Friday, 10th April, 2015: Literature 2(Essay) — 8.30am – 9.45am Literature 1(Obj) — 9.45am – 10.45am _____________________________ Monday, 13th April, 2014: Geography 2 (Essay) — 8.30am – 10.30am Geography 1 (Obj) — 10.30am – 11.30am _____________________________ Tuesday, 14th April, 2015 Physics 2 (Essay) — 8.30am – 10.30am Physics 1 (Obj) — 10.00am – 11.15am Geography 3 (Practical & Physical Geo) --- 1.00pm – 2.50pm _____________________________ Wednesday, 15th April, 2015 Chemistry 3 (Practical) (Alt A) — 8.30am – 10.30am (1st Set) Chemistry 3 (Practical) (Alt A) — 11.00am – 1.00pm (2nd Set) _____________________________ Thursday, 16th April, 2015 Government 2 (Essay) — 8.30am – 10.30am Government 1 (Obj) — 10.30am – 11.30am Physics 3 (Practical) ( Alt. B) — 08.30am – 11.15am (1st Set) Physics 3 (Practical) (Alt. B) — 11.40am – 3.25pm (2nd Set) Computer Studies (Practical) — 8.30am – 10.30am (1st Set) Computer Studies (Practical) — 11.00am – 1.00pm (2nd Set) _____________________________ Friday, 17th April, 2015 Foods & Nut 2 (Essay) — 8.30pm – 9.45pm Foods & Nut 1 (Obj) — 9.45pm – 10.45pm _____________________________ Monday, 20th April, 2015 Islamic Studies 2 (Essay) — 8.30am – 10.30am Islamic Studies 1 (Obj) — 10.30am – 11.20am Christian Religious Studies 2 (Essay) — 8.30am – 10.30am Christian Religious Studies 2(Obj) — 10.30am – 11.30am Chemistry 2 (Essay) — 1.00pm – 3.00pm Chemistry 1 (Obj) — 3.00pm – 4.00pm _____________________________ Tuesday, 21st April, 2015 Financial Accounting 2 (Essay) — 8.30am – 11.00am Financial Accounting 1(Obj) — 11.00am – 12.00pm Biology 2 (Essay) — 1.00pm – 2.40pm Biology 1(Obj) — 2.40pm. – 3.30pm _____________________________ Wednesday, 22nd April, 2015: Agric Science 3 (Practical) — 8.30am – 10.30am (1st Set) Agric Science 3 (Practical) — 11.00am – 1.30pm (2nd Set) _____________________________ Thursday, 23rd April, 2015: Mathematics 2 (Essay) — 8.30am – 11.00am Mathematics 1 (Obj) — 1.00pm – 2.30pm _____________________________ Friday, 24th April, 2015: Economics 2 (Essay) — 8.30am – 10.30am Economics 1 (Obj) — 10.30pm – 22.30pm _____________________________ Tuesday, 29th April, 2015 Office Practice 2 (Essay) — 1.00pm – 3.10pm Office Practice 1 (Obj) — 3.10 – 4.10pm _____________________________ Thursday, 30th April, 2015 Biology 3 (Practical) (Alt. A) — 8.30am – 10.30am Biology 3 (Practical) (Alt. B) — 10.30am – 12.30pm Literature 3 (Darama) — 1.00am – 3.30am _____________________________ Monday, 4th May, 2015 Further Mathematics 2(Essay) --- 8.30am – 11.00am Further Mathematics 1(Obj) — 2.30pm – 4.00pm _____________________________ Thursday, 5th May, 2015 Commerce 2 (Essay) — 1.00pm – 3.00pm Commerce 1 (Obj) — 3.00pm – 3.50pm _____________________________ Wednesday, 6th May, 2015 Agric Science 2 (Essay) — 8.30am – 10.40am Agric Science 1 (Obj) — 10.40am – 11.30am _____________________________ Friday, 8th May, 2015: Technical Drawing (Essay) – 1.00pm – 4.00pm _____________________________ Wednesday, 13th April, 2015 French 2 (Essay — 8.30am – 9.45am French 1 (Obj) — 9.45am – 10.45am _____________________________ - See more at: http://www.gurusfamily.net/news/topic.php?id=2579#sthash.ogQuysui.dpuf

SEPERATION TECHNIQUES

SEPARATION TECHNIQUES:
they include
*Separating funnel
*Chromatography
*Centrifugation
*Simple distillation
*Fractional distillation

The Theory
How is a homogeneous mixture different from a heterogeneous mixture?

Most materials in our surroundings are mixtures of two or more components. Mixtures are either homogeneous or heterogeneous. Homogeneous mixtures are uniform in composition, but heterogeneous mixtures are not uniform in composition.

Air is a homogeneous mixture and oil in water is a heterogeneous mixture. Homogeneous and heterogeneous mixtures can be separated into their components by several physical methods. The choice of separation techniques is based on the type of mixture and difference in the chemical properties of the constituents of a mixture.
What are types of separation techniques?

Various types of separation processes are:

Crystallization
Filtration
Decantation
Sublimation
Evaporation
Simple distillation
Fractional distillation
Chromatography
Centrifugation
Separating funnel
Magnetic separation
Precipitation

Let’s discuss some of the separation techniques

Using a separating funnel:

A separating funnel is used for the separation of components of a mixture between two immiscible liquid phases. One phase is the aqueous phase and the other phase is an organic solvent. This separation is based on the differences in the densities of the liquids. The liquid having more density forms the lower layer and the liquid having less density forms the upper layer.

Applications:

To separate a mixture of oil and water.
To separate a mixture of kerosene oil and water.

Chromatography:

Chromatography is a separation technique used to separate the different components in a liquid mixture. It was introduced by a Russian Scientist Michael Tswett. Chromatography involves the sample being dissolved in a particular solvent called mobile phase. The mobile phase may be a gas or liquid. The mobile phase is then passed through another phase called stationary phase. The stationary phase may be a solid packed in a glass plate or a piece of chromatography paper.

The various components of the mixture travel at different speeds, causing them to separate. There are different types of chromatographic techniques such as column chromatography, TLC, paper chromatography, and gas chromatography.

Paper chromatography is one of the important chromatographic methods. Paper chromatography uses paper as the stationary phase and a liquid solvent as the mobile phase. In paper chromatography, the sample is placed on a spot on the paper and the paper is carefully dipped into a solvent. The solvent rises up the paper due to capillary action and the components of the mixture rise up at different rates and thus are separated from one another.

Applications:

To separate colors in a dye.
To separate pigments from natural colors.
To separate drugs from blood.

Centrifugation:

Sometimes the solid particles in a liquid are very small and can pass through a filter paper. For such particles, the filtration technique cannot be used for separation. Such mixtures are separated by centrifugation. So, centrifugation is the process of separation of insoluble materials from a liquid where normal filtration does not work well. The centrifugation is based on the size, shape, and density of the particles, viscosity of the medium, and the speed of rotation. The principle is that the denser particles are forced to the bottom and the lighter particles stay at the top when spun rapidly.

The apparatus used for centrifugation is called a centrifuge. The centrifuge consists of a centrifuge tube holder called rotor. The rotor holds balanced centrifugal tubes of equal amounts of the solid-liquid mixture. On rapid rotation of the rotor, the centrifuge tubes rotate horizontally and due to the centrifugal force, the denser insoluble particles separate from the liquid. When the rotation stops, the solid particles end up at the bottom of the centrifuge tube with liquid at the top.

Applications:

Used in diagnostic laboratories for blood and urine tests.
Used in dairies and home to separate butter from cream.
Used in washing machines to squeeze water from wet clothes.

Simple distillation:

Simple distillation is a method used for the separation of components of a mixture containing two miscible liquids that boil without decomposition and have sufficient difference in their boiling points.

The distillation process involves heating a liquid to its boiling points, and transferring the vapors into the cold portion of the apparatus, then condensing the vapors and collecting the condensed liquid in a container. In this process, when the temperature of a liquid rises, the vapor pressure of the liquid increases. When the vapor pressure of the liquid and the atmospheric pressure reach the same level, the liquid passes into its vapor state. The vapors pass over the heated portion of the apparatus until they come into contact with the cold surface of the water-cooled condenser. When the vapor cools, it condenses and passes down the condenser and is collected into a receiver through the vacuum adapter.

Applications:

Separation of acetone and water.
Distillation of alcohol.

Fractional distillation:

Fractional distillation is used for the separation of a mixture of two or more miscible liquids for which the difference in boiling points is less than 25K. The apparatus for fractional distillation is similar to that of simple distillation, except that a fractionating column is fitted in between the distillation flask and the condenser.

A simple fractionating column is a tube packed with glass beads. The beads provide surface for the vapors to cool and condense repeatedly. When vapors of a mixture are passed through the fractionating column, because of the repeated condensation and evaporation, the vapors of the liquid with the lower boiling point first pass out of the fractionating column, condense and are collected in the receiver flask. The other liquid, with a slightly higher boiling point, can be collected in similar fashion in another

Applications:

Separation of different fractions from petroleum products.
Separation of a mixture of methanol and ethanol.

THE PERIODIC TABLE

PERIODIC LAW, in chemistry, law stating that many of the physical and chemical properties of the elements tend to recur in a systematic manner with increasing atomic number. Progressing from the lightest to the heaviest atoms, certain properties of the elements approximate those of precursors at regular intervals of 2, 8, 18, and 32. For example, the 2d element (helium) is similar in its chemical behavior to the 10th (neon), as well as to the 18th (argon), the 36th (krypton), the 54th (xenon), and the 86th (radon). The chemical family called the halogens, composed of elements 9 (fluorine), 17 (chlorine), 35 (bromine), 53 (iodine), and 85 (astatine), is an extremely reactive family.


Historical Development.

As a result of discoveries that firmly established the atomic theory of matter advanced by the British chemist and physicist John Dalton in 1803, scientists were able to determine the relative weights of atoms of the then known elements. The development of electrochemistry during this period by the British chemists Sir Humphry Davy and Michael Faraday led to the discovery of many additional elements. By 1829 a sufficient number of elements had been discovered to permit the German chemist Johann Wolfgang Döbereiner (1780-1849) to observe that certain elements with closely similar properties occur in triads, or groups of three, such as chlorine, bromine, and iodine; calcium, strontium, and barium; sulfur, selenium, and tellerium; and iron, cobalt, and manganese. Because of the limited number of known elements and the confusion that existed concerning the distinction between atomic weights and molecular weights, chemists were unable to grasp the significance of the Döbereiner triads.

The development of the spectroscope in 1859 by the German physicists Robert Wilhelm Bunsen and Gustav Robert Kirchhoff made possible the discovery of many more elements (see SPECTRUM). In 1860, at the first international chemical congress ever held, the Italian chemist Stanislao Cannizzaro clarified the fact that some of the elements-for example, oxygen-have molecules containing two atoms. This realization finally enabled chemists to achieve a self-consistent listing of the elements.

These developments gave new impetus to the attempt to reveal interrelationships among the properties of the elements. In 1864 the British chemist John A. R. Newlands (1837-98) listed the elements in the order of increasing atomic weights and noted that a given set of properties recurs at every eighth place. He named this periodic repetition the law of octaves, by analogy with the musical scales. Newlands's discovery failed to impress his contemporaries, probably because the observed periodicity was limited to only a small number of the known elements.


Mendeleyev and Meyer.

The chemical law that the properties of all the elements are periodic functions of their atomic weights was developed independently by two chemists: in 1869 by Dmitry Mendeleyev, a Russian, and in 1870 by Julius Lothar Meyer, of Germany. The key to the success of their efforts was the realization that previous attempts had failed because a number of elements were as yet undiscovered and that vacant places must be left for such elements in the classification. Thus, although no element then known had an atomic weight between those of calcium and titanium, Mendeleyev left a vacant space for it in his table. This place was later assigned to the element scandium, discovered in 1879, which has properties justifying its position in the sequence. The discovery of scandium proved to be one of a series of dramatic verifications of the predictions based on the periodic law, and validation of the law accelerated the development of inorganic chemistry.

The periodic law has undergone two principal elaborations since its original formulation by Mendeleyev and Meyer. The first revision involved extending the law to include a whole new family of elements, the existence of which was completely unsuspected in the 19th century. This group comprised the first three of the noble, or inert, gases (see NOBLE GASES), argon, helium, and neon, discovered in the atmosphere between 1894 and 1898 by the British physicist John William Strutt, 3d Baron Rayleigh, and the British chemist Sir William Ramsay. The second development in the periodic law was the interpretation of the cause of the periodicity of the elements in terms of the Bohr theory (1913) of the electronic structure of the atom (see ATOM AND ATOMIC THEORY).


Short-Form Periodic Table.

The periodic law is most commonly expressed in chemistry in the form of a periodic table, or chart. The so-called short-form periodic table, based on Mendeleyev's table, with subsequent emendations and additions, is still in widespread use. In this table the elements are arranged in seven horizontal rows, called the periods, in order of increasing atomic weights, and in 18 vertical columns, called the groups. The first period, containing two elements, hydrogen and helium, and the next two periods, each containing eight elements, are called the short periods. The remaining periods, called the long periods, contain 18 elements, as in periods 4 and 5, or 32 elements, as in period 6. The long period 7 includes the actinide series , which has been filled in by the synthesis of radioactive nuclei through element 103, lawrencium. Heavier transuranium elements , atomic numbers 104 to 112, have also been synthesized.

The groups or vertical columns of the periodic table have traditionally been labeled from left to right using Roman numerals followed by the symbol a or b, the b referring to groups of transition elements . Another labeling scheme, which has been adopted by the International Union of Pure and Applied Chemistry (IUPAC), is gaining in popularity. This new system simply numbers the groups sequentially from 1 to 18 across the periodic table.

All the elements within a single group bear a considerable familial resemblance to one another and, in general, differ markedly from elements in other groups. For example, the elements of group 1 (or Ia), with the exception of hydrogen, are metals with chemical valence of +1, while those of group 17 (or VIIa), with the exception of astatine, are nonmetals commonly forming compounds in which they have valences of - 1.


Electron Shell Theory.

In the periodic classification, noble gases, which in most cases are unreactive (valence = 0), are interposed between highly reactive metals that form compounds in which their valence is +1 on one side and highly reactive nonmetals forming compounds in which their valence is -1 on the other side. This phenomenon led to the theory that the periodicity of properties results from the arrangement of electrons in shells about the atomic nucleus. According to the same theory, the noble gases are normally inert because their electron shells are completely filled; other elements, therefore, may have some shells that are only partly filled, and their chemical reactivities involve the electrons in these incomplete shells. Thus, all the elements that occupy a position in the table preceding that of an inert gas have one electron less than the number necessary for completed shells and show a valence of -1, corresponding to the gain of one electron in reactions. Elements in the group following the inert gases in the table have one electron in excess of the completed shell structure and in reactions can lose that electron, thereby showing a valence of +1.

An analysis of the periodic table, based on this theory, indicates that the first electron shell may contain a maximum of 2 electrons, the second builds up to a maximum of 8, the third to 18, and so on. The total number of elements in any one period corresponds to the number of electrons required to achieve a stable configuration. The distinction between the a and b subgroups of a given group also may be explained on the basis of the electron shell theory. Both subgroups have the same degree of incompleteness in the outermost shell but differ from each other with respect to the structures of the underlying shells. This model of the atom still provides a good explanation of chemical bonding.


Quantum Theory.

With the development of the quantum theory and its application to atomic structure by the Danish physicist Niels Bohr and other scientists, most of the detailed features of the periodic table have found a ready explanation. Every electron is characterized by four quantum numbers that designate its orbital motion in space. By means of the selection rules governing these quantum numbers and the exclusion principle of Wolfgang Pauli, which states that two electrons in the same atom cannot have all four quantum numbers the same, physicists can determine theoretically the maximum number of electrons required to complete each shell, confirming the conclusions inferred from the periodic table.

Further development of the quantum theory revealed why some elements have only one incomplete shell (namely, the outermost, or valence, shell), whereas others may have incomplete underlying shells as well. In the latter category is the group of elements known as the rare earth elements , which are so similar in properties that Mendeleyev had to assign all 14 to a single place in his table. The rare earth group includes the elements in the lanthanide series .


Long-Form Table.

The application of the quantum theory of atomic structure to the periodic law has led to the redesign of the periodic table in the so-called long form, which emphasizes this electronic interpretation. In the long-form table, each period corresponds to the building up of a new electronic shell. Elements that are directly in line with each other have strictly analogous electronic structures. The beginning and end of a long period represent the addition of electrons in a valence shell; in the central portion the number of electrons in an underlying shell increases.

The periodic law has been found to correlate a great many different properties of the elements, including such physical properties as melting and boiling points, densities, crystal structures, hardness, electrical conductivity, heat capacity, and thermal conductivity, and such chemical properties as reactivity, acidity or basicity, valence, polarity, and solubility.

PROPERTIES OF ELEMENT IN THE PERIODIC TABLE
The properties of the elements exhibit trends or periodicity. These trends can be predicted using the periodic table and can be explained and understood by analyzing the electron configurations of the elements. Elements tend to gain or lose valence electrons to achieve stable octet formation. Stable octets are seen in the inert gases, or noble gases, of Group VIII of the periodic table. In addition to this activity, there are two other important trends. First, electrons are added one at a time moving from left to right across a period. As this happens, the electrons of the outermost shell experience increasingly strong nuclear attraction, so the electrons become closer to the nucleus and more tightly bound to it. Second, moving down a column in the periodic table, the outermost electrons become less tightly bound to the nucleus. This happens because the number of filled principal energy levels (which shield the outermost electrons from attraction to the nucleus) increases downward within each group. These trends explain the periodicity observed in the elemental properties of atomic radius, ionization energy, electron affinity, and electronegativity.

Atomic Radius

The atomic radius of an element is half of the distance between the centers of two atoms of that element that are just touching each other. Generally, the atomic radius decreases across a period from left to right and increases down a given group. The atoms with the largest atomic radii are located in Group I and at the bottom of groups.

Moving from left to right across a period, electrons are added one at a time to the outer energy shell. Electrons within a shell cannot shield each other from the attraction to protons. Since the number of protons is also increasing, the effective nuclear charge increases across a period. This causes the atomic radius to decrease.

Moving down a group in the periodic table, the number of electrons and filled electron shells increases, but the number of valence electrons remains the same. The outermost electrons in a group are exposed to the same effective nuclear charge, but electrons are found farther from the nucleus as the number of filled energy shells increases. Therefore, the atomic radii increase.

Ionization Energy

The ionization energy, or ionization potential, is the energy required to completely remove an electron from a gaseous atom or ion. The closer and more tightly bound an electron is to the nucleus, the more difficult it will be to remove, and the higher its ionization energy will be. The first ionization energy is the energy required to remove one electron from the parent atom. The second ionization energy is the energy required to remove a second valence electron from the univalent ion to form the divalent ion, and so on. Successive ionization energies increase. The second ionization energy is always greater than the first ionization energy. Ionization energies increase moving from left to right across a period (decreasing atomic radius). Ionization energy decreases moving down a group (increasing atomic radius). Group I elements have low ionization energies because the loss of an electron forms a stable octet.

Electron Affinity

Electron affinity reflects the ability of an atom to accept an electron. It is the energy change that occurs when an electron is added to a gaseous atom. Atoms with stronger effective nuclear charge have greater electron affinity. Some generalizations can be made about the electron affinities of certain groups in the periodic table. The Group IIA elements, the alkaline earths, have low electron affinity values. These elements are relatively stable because they have filled s subshells. Group VIIA elements, the halogens, have high electron affinities because the addition of an electron to an atom results in a completely filled shell. Group VIII elements, noble gases, have electron affinities near zero, since each atom possesses a stable octet and will not accept an electron readily. Elements of other groups have low electron affinities.

In a period, the halogen will have the highest electron affinity, while the noble gas will have the lowest electron affinity. Electron affinity decreases moving down a group because a new electron would be further from the nucleus of a large atom.

Electronegativity

Electronegativity is a measure of the attraction of an atom for the electrons in a chemical bond. The higher the electronegativity of an atom, the greater its attraction for bonding electrons. Electronegativity is related to ionization energy. Electrons with low ionization energies have low electronegativities because their nuclei do not exert a strong attractive force on electrons. Elements with high ionization energies have high electronegativities due to the strong pull exerted on electrons by the nucleus. In a group, the electronegativity decreases as atomic number increases, as a result of increased distance between the valence electron and nucleus (greater atomic radius). An example of an electropositive (i.e., low electronegativity) element is cesium; an example of a highly electronegative element is fluorine..