ELEMENTS AND THEIR SYMBOLS
An element is a pure chemical substance which cannot be split into simpler substance by a simple chemical process.Examples of element, are iron, silver, gold, copper, oxygen and hydrogen.
Names and symbols of elements
All known elements have names and these names are represented by a letter is commonly known as chemical symbol
Chemical symbols is letters which represent a name of an element.
Or
Chemical symbols is abbreviations or show the representation of the name of an element
Chemical symbols which are used to represent the name of elements commonly it is the first letter of an element or sometimes can be the first letter and second letter of an element.
But some of elements their chemical symbols are derived from Latin or Greek names of the element for example symbol of sodium is Na (natrium) for gold is Au (aurum).
Criteria for assigning symbols
- Symbols of one element is derived from the first letter of the English name
Carbon. C
Iodine. I
Flourine . F
2. Elements with the same first letter such as carbon and calcium usually the second letter from the name is used with the first one the first letter will be capital, second will be small letter.
Name. Symbols
Carbon. C
Calcium. Ca
3. symbol of elements can be derived from Latin names instead of the common Englis name
IMPORTANCE OF CHEMICAL SYMBOLS
- Help to understand quickly element being referred to instead of having to memorize the full namess.
- Symbols make possible to write equations in abbreviation form
- The quantity of element being referred to can be known readily.
Two or more elements can be combined to form compounds or mixture.
COMPOUNDS
compound is a pure substance that is made up of more than one elements in a chemical combination.
This combination of element is always in fixed ratio for example, what is made up of two parts of hydrogen for every one part of oxygen.
Other examples of compounds are sugar, salt and carbon dioxide.
Since compound is chemically combined can be separated by chemical means.
MIXTURE
Mixture is a physical combination of two or more substances in any ratio.
Since mixture is not chemically combined can you be separated by physical means
Mixture can a beam liquidy-liquid example of oil and water, solid liquid For example muddy water, or salt and Sand
TYPES OF MIXTURE
1. Homogeneous mixture
2. Heterogeneous mixture
Homogeneous mixture
Is a mixture which has uniform composition, appearance and properties.
Example a small amount of common salt dissolved in water.
Heterogeneous mixture
is the mixture which has different composition, appearance and properties at various points in the mixture.
Example mixture of ice and water at one point we find a solid while to another with find liquids.
SOLUTION
– Is a mixture of two or more substances.
– Is a homogeneous mixture of two or more substances.
– Is a mixture of solute and solvent.
That is solution=Solute+Solvent
Solute
Is a substance which dissolves in a solvent.
E.g. sugar, salt.
Solvent
Is a substance that dissolves a solute.
Examples of solutions.
-Alcohol and water
-Salt and water
-Iodine and water
Classification of solution based on solvent solute ratio.
There are 3 categories;
->Unsaturated solution
– The one that contains less solute then it can dissolve.
– The one in which more solute can dissolve at a given temperature.
->Saturated solution
– The one which has enough solute, no more solute can dissolve at the same temperature.
E.g. you shake some sugar in water it will dissolve and if you add more it will remain undissolved until it is heated.
->Supersaturated solution
Is a solution which contains more solute than it can hold at the same temperature.
It can be made by heating the solution and solute until it is saturated.
Classification based three states of matter.
Two or more solutes mixed together
->Brass- solution of zinc and copper.
->Bronze- solution of tin and copper.
->Steel- solution of phosphorous, sulphur, nickel, carbon, iron.
*Liquid solution E.g. Salt and water
*Gaseous solution-Two or more gases mixed together.E.g. air
SUSPENSION
Is a liquid containing solid particles spread throughout it and which settle at the bottom on standing.
Suspension are heterogeneous mixtures.
Suspensions in real life
Many medicines are suspensions especially those containing the label “shake before use”
Examples of suspension;
-Syrup
-Paint pigment in oil
-Porridge; suspension of flour in water
-Mist; suspensions of water particles in air
METHODS OF SEPARATING MIXTURES
-Decantation
-Filtration
-Evaporation
-Simple distillation
-Fractional distillation
-Sublimation
-Chromatography
-Magnetic separation
-Funnel
-Crystallization
-Solvent extraction
Decantation is the process of slowly pouring out the liquid in a clean beaker and leaving out behind the sediment’s eg.muddy, water
Application-Making tea or coffee you can separate tea/coffee by this process
Decantation involves two steps
- a) Leaving the mixture to stand so making the solid particles settle at the bottom.
- b) Pouring the liquid into other clean containers.
Filtration is the process of removing suspended particles from a liquid by allowing the liquid to pass through a porous material such as filter paper and leaving the solid behind the filter paper.
The liquid that passes through the filter paper is called filtrate.
The solid that remains on the filter paper is called residue.
Application-Filtering drinking water
*Evaporation is the process of obtaining solid solute by leaving solvent.
Example;
Separation of salt from salt solution
Separation of sugar from sugar solution
APPARATUS:
Bunsen flame, tripod stand, wire gauze, water bath that is a beaker and evaporation basin.
PROCEDURE:
Place the wire gauze on top of tripod stand takes a beaker with some water and places the wire gauze and place the evaporating basin on top of the containing water. Heals the water in a beaker to form steam which in turn boils the solution on the basin. The water will evaporate, the solid crystals will remain.
APPLICATON:
Separation of salt from sea water.
Simple distillation
Is the process of boiling liquid to form vapor and then cooling the vapor to obtain liquid. The process is applicable to get pure solvent and solute from a solution.
-Solute will remain in a distilling flask and solvent is collected in the beaker.
Experiment
Aim- To obtain pure water from copper sulphate solution.
Procedures
- The solution is heated in the flask.
– It boils and steam rises into condenser.
– The salt is left behind.
- The condenser is cold, so the steam condenses to water in it.
- The water drips in the beaker, it is completely pure.
This method can also be used to obtain pure water from sea water.
Note: During distillation, evaporation and condensation take place at the same time but at different parts of the apparatus. The pure liquid is collected is called distillation.
Funnel separation
It is used to separate two immiscible liquids. For example the mixture of oil and water, the oil floats to the top, while water is at the bottom.
When the top is opened, the water runs out. The top is closed again when all the water has gone. Their separation is based on differences in their densities.
Sublimation
It is the process where by a substance changes from solid to gas.
- A) Separation of ammonium chloride from sodium chloride.
If a mixture of ammonium chloride and sodium chloride is heated, the ammonium chloride turns directly to vapor but the sodium chloride remains. When the vapor is cooled, solid ammonium chloride collects to leave sodium chloride.
- B) A mixture of iodine and sand can be separated by sublimation where iodine sublime leaving the sand behind.
CHROMATOGRAPHY
Is the method used to separate a mixture of colors.
E.g. It separates a colored substance from black ink.
The components separate by passing through a medium.
The components move at different rates over a material such a filter paper.
FRACTIONAL DISTILLATION
Is which the method used to separate mixture of two solvents which differ in boiling points.
E.g. a mixture of alcohol and water.
Petroleum can be spilt up into various products like petrol, diesel, and kerosene by fractional distillation
Separating mixture of air.
Experiment:
Separation of alcohol from water.
Alcohol boils at 780C and water boils at 1000C.
By using thermometer, temperature can be regulated to allow only alcohol to boil and form to vapor before water.
Therefore alcohol is collected before water.
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