Separation Techiques

Separation techniques is basically a set of skills that uses processes and properties of the substances to extract a particular substance,either for sampling or other purposes....

The techniques are:

• Filtration
• Evaporation to dryness
• Distillation(consisting of simple distillation and fractional distillation)
• Magnetic attraction
• Crystallisation
• Chromatography 

Filtration

With the help of a funnel paper,we filter out the substance with a bigger particle size and this is called the residue as it remains while the substance that is smaller in particle size drips into the test tube and this is called the filtrate as this is the wanted substance filtered out.Like filtering Sand and gravel, broken glass bits and remnants from dead organisms to obtain water, oil, salt, alcohol in a mixture of liquid and solid.

Evaporation to dryness
This is to obtain the solute that is insoluble in the solvent by heating it over a small flame and leaving the solvent to dry.One example is heating a salt solution to evaporate all the water and obtain the salt crystals. Disadvantages are any soluble impurities will be deposited along with the required solid not suitable for all solutes and sugar decomposes to give water and carbon.


Fractional distillation
It increases surface area for vapour of different temperature to condense to ensure that only the hottest vapours reach the top of the column and followed by all the other cooler vapours.Used to separate oils in crude oil.
Simple distillation
Solution is heated and liquid with difference of 20 degrees evaporates in a flask and condenses into water when in contact with the cooler surface of the Liebig condenser wrapped around the tubing to drip into the distilling flask at the end.


Magnetic attraction

Magnetic Substances are:

• Iron
• Nickel
• Cobalt
• Steel (alloy of iron)

It is used to remove magnetic material like scrap steel and iron at the junkyard to recycle them.

Newark Slough is a wide tidal waterway that starts in San Francisco Bay south of the Dumbarton Bridge, running through the Refuge around its salt ponds(saturated solutions), and ending up at Thornton Avenue.In crystallization,we heat the solution until a saturated solution is obtained and salt crystals are formed and then,filtered out.

Chromatography gives quick results (< 15 min) and is easy to handle and requires small amounts of mixtures.It identifies poisons/drugs in urine samples and detect traces of unpermitted additives in foodstuffs.It separates the components in a sample identify the number of substances in a sample and the substances in a sample so as to determine if the sample is pure.

Source:google image,youtube and ivle powerpoints

Reflection

As you can see,learning about separation techniques is not hard enough,however,in forensics science,it is more of the extraction of samples and data that is more tedious and one has to be observant and careful in not contamination the samples.Chromatography is a simple trick used by forensic scientists to determine the purity of the sample.Other than that,I know all these skills will come in handy for the future as we need to do more freestyle practicals and more complicated experiments(I will talking about them in the science eureka section,so look forward).For now,let's do the guided experiments in our list and learn through theory....than practical

 

Term 3-elements,compound and mixture

Elements

An element is a substance which cannot be broken down into two or more simpler substances by chemical methods.

Elements are the simplest kind of matter.

There are more than 100 elements in the universe.

All discovered elements are listed in the Periodic Table.

The Periodic Table

As you can see,elements are represented by a unique symbol,usually consisting of one or two letters,some are easy to remember as they are the initial of english words but other words are Latin,so it depends on each individual.

Classifying elements

The periodic table is a very organised system.

Elements have been placed systematically into the Periodic Table according to their properties.

Scientists have classified elements into 2 main groups, the metals and non-metals.

Each vertical column is called a period. Each group’s number is reflected at the top of the periodic table.

Elements in the same group have similar properties and will undergo the same type of chemical reactions. Each group has its own unique properties.

Each horizontal row is called a group.

The periods are numbered from the top row down.

Elements in a period from left to right show a gradual change from metallic to non-metallic_.

Elements to the left of the zig-zag line in the Periodic Table are metals, while those to the right of the zig-zag line are non-metals.

Compounds

A compound is a substance containing two or more elements chemically joined together.

The properties of the compound formed have different properties from the constituent elements

Compounds cannot be broken down by physical methods,it 
can ONLY be broken down by chemical methods.

It is in fixed proportion by ratio.

Mixture

It is the only impure substance out of the three classification,elements and compounds are pure while only mixture are impure...

A mixture consists of two of more different substances that are mixed but not chemically joined together.

Simplest examples:

—  a mixture of 2 elements
—a mixture of 2 compounds
—a mixture of an element and a compound

¢Air

—mixture of gases

—contains N2 , O2 , Ar, CO2 , H2O (gas), methane and other inert gases.

—

¢ Seawater

—exist as liquid

—contains water and sodium chloride

—

¢Brass

—exist as solid

—mixture of copper and zinc

A mixture has variable composition. It can only be separated by physical means like distillation and filtration.

Solutions are also mixtures.Now,I will be talking about them......

•All solutions consist of 2 parts

–Solvent (the substance that does the dissolving, makes up the majority of the solution – usually liquid, but can also be solid or gas)

–Solute (the substance that dissolves – can be solid, liquid or gas)

Examples

Iodine is a non-metallic element that sublimes when heated to form a violet vapour.

When dissolved in ethanol, it forms tincture of iodine, used as an antiseptic.

Solubility 

•The solubility of a substance in a solvent is the maximum quantity of that substance which can dissolve in 100 g of the solvent at a given temperature

•(units: g / 100 g)

Types of solution

•Copper(II) sulfate has a solubility of 32 g /100 g in water (at 20°C)

•Copper(II) sulfate has a solubility of 32 g /100 g of solvent (at 20°C)

•100 g of water (100 ml)

–2 g of copper(II) sulfate-dilute solution

–30 g of copper(II) sulfate-concentrated solution

–32 g of copper(II) sulfate-saturated solution

–35 g of copper(II) sulfate-suspension 

Factors affecting solubility

•Type of solute

type of solvent 

•Temperature of solvent

•Pressure of surroundings

Suspension

When the amount of substance present is over its solubility limit,

the substance does not dissolve in the solvent

•Factors affecting rate of dissolving

–Temperature of solvent

–Particle size of solute

Stirring

Source: Powerpoints in Ivle

Reflection

I feel that one has to fluent in understanding these properties to relate them to real life applications like the swirling of lemon tea in the canteen before taking a sip,the making of alloys like brass instruments in companies and the chemical reactions that takes place when rockets,Apollo, is able to launch.In conclusion,besides studying the properties of the classification and absorbing them,i should study the link to situations when we have indigestion,a city having more solubility of air than a village and so more.....into my aces......:DDDD

units

Density Intro
DENSITY is a physical property of matter, as each element and compound has a unique density associated with it. Density defined in a qualitative manner as the measure of the relative "heaviness" of objects with a constant volume.In other words,it is the the amount of mass per unit volume,therefore,the equation is D=M/V.D is density,M is mass and V is volume.These are some of the examples:

Densities of Common Elements and Compounds
Substance	Density grams per mL
Pine wood	0.35 -0.50
Water	1.00
Salt, NaCl	2.16
Aluminum, Al	2.70
Iron, Fe	7.80
Gold, Au	19.30
Mercury, Hg	13.5

Some experiments to try out:
http://www.elmhurst.edu/~chm/demos/index.html-Floating Eggs 
http://www.elmhurst.edu/~chm/demos/index.html-Lava Lamp
http://www.elmhurst.edu/~chm/demos/index.html-Underwater Smokestack

Vocabulary Required:

SIGNIFICANT DIGITS	VOLUME	DENSITY
ACCURACY	DENSITY OF WATER	MASS
PRECISION	MENISCUS	DERIVED UNITS

Displacement

When trying to measure the volume of an irregularly shaped object, the "water displacement method" is the most commonly used technique and the one you will use most often in this chemistry course. The procedure for the water displacement method is listed below.

PROCEDURE:
1) Find a graduated cylinder that will be large enough to fit the object(s) being measured.
2) Fill this graduated cylinder enough so that when placed in the graduated cylinder, the object(s) in question will be fully submerged in the water. Also be careful not to put in so much water that the water level will rise past the graduated cylinder’s markings when the object(s) are placed in the graduated cylinder. You must use your own judgment to determine what amount of water meets these requirements.
3) After filling the graduated cylinder to a satisfactory level, record the volume of the water as (a) in your data. Make sure to read the meniscus when determining volume.
4) After the water’s volume has been recorded, carefully place the object(s) in the graduated cylinder and record this volume as (b) in your data.
5) In order to calculate the volume of the irregularly shaped object(s), subtract the volume of the water alone from the volume of the water and object(s) [(b) – (a)].


Hints and Tips:

1) All objects must be fully submerged when using the "water displacement method".
2) If a solid substance is soluble in water, another liquid may be substituted when using the "water displacement method".
3) Use a smaller graduated cylinder whenever possible regarding the measurement of a substance's volume. The smaller a graduated cylinder is, the more accurate your measurement can be.
4) Density of water is 1.00 g/cm³.
5) Rust is a source of error when calculating density of metals.
6) Remember to mass all objects only when dry.

Standard units
The International System of Units (abbreviated SI from French: Système international d'unités) is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. It is the world's most widely used system of measurement, both in everyday commerce and in science as The International System of Units (abbreviated SI from French: Système international d'unités) is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. It is the world's most widely used system of measurement, both in everyday commerce and in science.

SI base units^[10][11]

Name	Unit symbol	Quantity	Typical Symbol for Variables
metre	m	length	l (a lowercase L)
kilogram [Notes 1]	kg	mass	m
second	s	time	t
ampere	A	electric current	I (a capital i)
kelvin	K	thermodynamic temperature	T
candela	cd	luminous intensity	Iv (a capital i with lowercase non-italicized v subscript)
mole	mol	amount of substance	n

Reflections-
Firstly,I feel that that standard units are very important as they are indicators of the sample size used by scientists,other than that,it is essential that scientists over the world accepts a common unit as there are many scientists in the world and there are many discoveries that are continuously explored,if scientists use an inch or other unknown units instead of centimeters,then,their records would not be understood and developed on by other scientists.Transparency is important in the intellectual field of science today,many of the scientists work as a team on different aspects and then,comply their information to make a breakthrough.As we can see,the invention of standard units prevent the confusion and conflicts over different measurements used.
Secondly,i feel that density is something we all must know as it is an indispensable property in our liquids,gases and solids.Density clears my doubt of why certain objects sink and why some people who are taller are lighter than those who are shorter(no offense).So basically,it is another property factories have to consider before making their product.:DDD
THE END