Chemistry‎ > ‎

Terminology. A-K.

posted Nov 30, 2015, 11:55 PM by Upali Salpadoru   [ updated Dec 13, 2016, 12:59 PM ]

                          A


  • ATOMS.


The smallest part of an element





Fig. The lightest two atoms , Hydrogen and Helium structures.





  • ACID

    Acids are a group of chemicals that have some specific properties.

  1. They have a sour taste. (WARNING No lab chemical should ever be  tasted.)

  2. Especially the concentrated acjds are highly corrosive and must be handled only by experienced people. Water should never be added to strong acids. Dilution is done by adding acid to water.

  3. Turns blue litmus paper to red.

  4. pH value is less than 7.

  5. Reacts with most metals releasing Hydrogen.

  6. Reacts with carbonates to give carbon dioxide.

  7. Reacts with bases forming salt and water.

  8. Acidic properties are due to the presence of Hydrogen ions in excess.

  • ACIDIC

This is an adjective which means that the substance has the properties of an acid.

Lime juice,vinegar are acidic substances. They produce H+ ions.

.For example you cannot say, Soil is an acid; but you can say "the soil is acidic". It is not quite right to call "vinegar is an acid". It has only about 4% acetic acid. The rest is mainly water.


  • ACID SALT

 A salt in which only some of the replaceable Hydrogen atoms have been removed.


  • ACID RAIN

Rain water that exhibit acidic properties due to the dissolving of acidic oxides  present in the atmosphere.


  • ACTIVATION ENERGY                                

Even in a reaction where chemical energy is released as heat, in order to initiate the reaction some energy is necessary. This energy is called the Activation energy.





  • ALCOHOL.

  • Canvas.jpg


A group of organic chemicals with an (OH) hydroxyll radical


Fig.Ethanol ( ethyl alcohol) is an example.


  • ALKALI

A chemical having a pH no. higher than 7. A soluble  oxide or a hydroxide of a metal or a positive radical like NH3+ (Ammonium)

They have hydroxyl OH - ions in excess.

eg. A sample of soil may be acidic or alkaline.


  • ALKANE SERIES

Hydrocarbons of the series, Methane - CH4   , Ethane- C2H6, Propane- C3H8……………etc,                General formula:-  CnH2n+2

    Examples:-  Methane CH4  ,   Ethane C2H6   etc.


  • AEROSOL

     A mixture formed when a gas contains fine particles of solid or liquid suspended .                              eg.  Smoke, Mist.



  • ALLOY

When two metals of the solid state are melted, mixed and condensed, what results is an alloy. These may be considered as homogenous mixtures although some chemical bonds may also be present.

Eg. Brass, consists of copper and zinc.


  • ALPHA DECAY

ALUM

A double salt an examples:-

Formula  Potash alum , Chrome alum.

Potash alum.       K2SO4. Al2 (SO4)3.24H2O   .


  • ANHYDROUS

Chemicals free from attached water molecules. Water molecules are necessary to form some crystals

Hydrated copper(II) sulfate, CuSO4.5H2Os, blue colour.

When unhydrated colour changes to white..

  • ANODE

The electrode of an electrolytic cell where oxidation takes place. (Opposite – cathode)

  • AVOGADRO LAW

In the case of ideal gases, equal volumes at the same temperature and pressure have the same number of molecules.


  • ACTIVITY SERIES

       Metals arranged according to the increasing order of reactivity with acids         and other  substances.

       Li K Sr Ca Na Mg Al Zn Cr Fe Cd Co Ni Sn Pb H2 Sb As Bi Cu Hg Ag Pt Au


  • AGAR AGAR

      A seaweed extract to get a jelly.


  • AMALGAM

      An alloy made with mercury.    


  • ANIONS

       An atom or a group of atoms that have gained electrons. They have a negative                           charge. They move towards the positive charge.    eg, Cl-,  SO42-,    opposite.- cation


  • ANODE

        In electrolysis, the terminal where electrons are given out to the electrolyte; where                    oxidation takes place.


  • ANODISING

        Treating metals, Usually aluminium,  in an electrolytic process making the relevant part the anode. This process oxidises the surface making it more resistant to reactions.

  • AQUEOUS SOLUTION

      A substance dissolved in water.


  • ATOM

        May be considered as the smallest, neutral part of an element. They have sub atomic particles.


  • ATOMIC NUMBER

This is a characteristic of an element and is equal to the number of protons inside the nucleus of its atoms.

It is represented by the symbol Z. This is also the same as the number of electrons in a



B

  • BAKING POWDER

A leavening agent  used in making cakes.  Main constituent of the mixture is Sodium hydrogen carbonate. ( Sodium bi-carbonate) 

In addition to this there will be an acidic powder and some starch.  Starch is added to dough in order to release carbon dioxide gas to get the spongy effect.   Even in the absence of an acid Sodium hydrogen carbonate can break down on heating.

2 NaHCO3(s) CO2(g) + H2O(g) + Na2CO3(s)
  • BASE   
An Oxide, or a hydroxide of a metal.  If they dissolve in water they form alkalis. Ammonium hydroxide is also an alkali.                                      
                                                                                                                  
  • BOND

         A chemical bond describes how atoms are attached to form molecules.

         (Go to:- Covalent compounds)

i.     Covalent bond.

Atoms are joined together by electron sharing  This is usually shown by a short line between the atomic symbols.  Eg. H2 as   H – H,    

Carbon dioxide as     O=C= O       While the bond in Hydrogen molecule is a single bond oxygen atoms in carbon dioxide are held by double bonds.

ii.     Ionic bond.

If an atom donates an electron it becomes a positive ion.  Na – e = Na+

If an atom gains an electron it becomes a negative ion.   Cl + e = Cl-

These ions having opposite electrical charges attract forming ionic compounds.

NaCl.

  • BUFFER SOLUTION
buffer solution is one in which the pH of the solution is "resistant" to small additions of either a strong acid or strong base.

C

  •  CARBON


A black non  metallic element.  Coal and Graphite are forms of carbon. Diamond is a crystalline form of this.    6C12

  • CARBON CYCLE
Carbon in the Carbon dioxide in the air is absorbed by the plants during photosynthesis. This is given out during respiration of all living things. This is called the Carbon Oxygen cycle.

  • CARBON DATING

An isotope of carbon , C14   is tested to determine the age of ancient artifacts.            

  • CARBONATES

These may be considered as the salts of carbonic acid.

Eg. Sodium carbonate Na2 CO3 ,   Calcium carbonate   Ca CO3

  • CATALYST

An agent that can change the speed of a chemical reaction. 

The exhaust fumes produced by motor cars contain the deadly gas carbon monoxide.  There is a converter that converts this gas to carbon dioxide which uses  iron oxide as a catalyst. As the catalyst is not consumed it has a life time of  about 10 years.

CFC

Chloto Fluoro Carbon. This is the compound present in spray cans which destroy the ozone layer.

  • COLLOIDS

These are mixtures with properties on the borderline between homogeneous and heterogeneous.

  • COMBUSTION

A chemical change where a substance combines with oxygen releasing an amount of heat which may produce a flame.

Motor cars are powered by Internal combustion engines where the burning is inside the cylinders.

  • COMPOUND

A pure substance made up of more than one element.  The properties of a compound differs from that of the elements in it.

Eg. Water , which has hydrogen and oxygen combined.  H2O

  • CONCENTRATION
 This may be given as the mass of solute dissolved in a definite volumme of the solution. Usually as the g/L  (grams per litre).
  • CORROSION

                  Fig. Electrochemical corrosion.

Rusting of iron is a form of corrosion. Iron atom gives out 2 electrons to acidified water and the ion thus formed combines with oxygen and water.  So rust is a hydrated oxide of iron.

D

  • DECOMPOSITION

Breaking down of a compound into simpler substances.

Eg.    Water =  Hydrogen + Oxygen

DEHYDRATION

Removal of water from a compound.

  • DELIQUESCENT

 A substance that absorbs water and dissolves in it.

  • DESICCATOR

This is usually a sealed glass container used to keep an object or substances free from moisture. It will have a substance like silica gel or calcium chloride , that can absorb water vapour.

  • DETERGENT

A substance used for removing greasy matter.

  • DIAMOND

A crystalline form of carbon.

  • DISPLACEMENT REACTION

A chemical reaction where one substance gets displaced due to the addition of another substance.  Type equation:-  AB  +  C  =  AC  + B

                  eg.   2HCl + Mg  =  MgCl2 + H2     

  • DISTILLATION

A method of separating two miscible liquids by evaporating and condensing.

eg. Distillation of alcohol from a dilute solution.

  • DISTILLATE

The liquid produced by distillation.

E

  • EMULSION
  •  This is formed when two liquids are thoroughly mixed. They do not separate though immiscible. . The droplets cannot be separated by filtering. An emulsion can scatter the light passing through unlike a true solution. Tyndall effect.     
         eg   Mayonnaise., Paint.

  • EPSOM SALT
A common name for Magnesium sulphate. MgSO4
  • ESTER
An organic compound formed by an acid and an alcohol.
ETHENE (ETHYLENE)
Simplest Alkene with two carbon atoms.


  • ETHONOIC ACID
Ascetic acjd.    CH3CH2OH

  • EVAPORATION

A change of state. A liquid changes to a gas. Liquid molecules escape from the uncovered upper surface. This is not the same as boiling, where liquid molecules change to gas while inside the liquid.


  • ENDOTHERMIC REACTION

A reaction that absorbs energy from the environment. Photosynthesis is an example.

  • EXOTHERMIC REACTION

Chemical reactions are usually accompanied by energy changes.. Either heat is given out as when quick lime , calcium oxide,  is added to water or  heat is absorbed when lime stone calcium carbonate is heated to break it down to the oxide.

       Exothermic reaction:-   CaO + H2O =  Ca (OH)2                                                        Opposite:-Endothermic reaction…CaCO3 = CaO + CO2

F

  • FERMENTATION

A very slow chemical reaction promoted by organic catalysts such as zymase. Yeast and some bacteria are capable of producing these for the purpose of respiration without oxygen.

       Some fermentation reactions

Milk is converted to yogurt by lactobacillus.

Yeast (Sachromyces) ferments sugar ethanol and carbon dioxide.  This is used in leavening of bread and in the brewing of beer and wine.                     Glucose  =  ethanol        +   carbondioxide.

                     C6H12O6 → 2 C2H5OH + 2 CO2

  • FELDSPAR

 A common pink coloured rock mineral which is an important constituent in granite.  About 60% of the earth’s crust is feldspar which withers to form kaolin.     This is an important   raw material for ceramics.     Formula    KAlSi3O8  or.. NaAlSi3O8 or.. CaAl2Si2O8

FIRE EXTINGUISHER

There are two main types. 1. Soda acid fire extinguisher  2. Foam fire extinguisher.

fire.jpg

Fig. A model fire extinguisher.

When the plunger is pressed the sulphuric acid comes in contact with the soda solution and reacts to form carbon dioxide gas. This gives the pressure to spray the solution on to the fire.

  • FLAME TEST

Paint.jpg

A little bit of the susbstance given is taken to the tip of a cleaned platinum wire and held into the gas flame. From the colour we can identify the metallic radicle.

  • FOAM

We often see bubbles in liquids. This may be a dissolved gas coming out. But if you stir a mixture of liquid and a gas thoroughly it may hold the gas bubbles.

Eg. Sea foam in wave breakers of the sea.   Lather with soap and water.

  • FURAN





Furan is a chemical that forms in some foods during cooking at high temperatures.

Furan is a clear, colorless, flammable liquid cyclic ether.. Inhalation exposure to this substance causes eye and skin irritation and central nervous system depression.

This is believed to be carcinogenic.

Fig. The amount of furan formed at different temperatures with food having different pH values.






G


  • GALVANIZING

The process of applying a covering of zinc on iron is called galvanizing iron. Here Zinc is sacrificed to prevent iron.

GLASS

The main ingredient used in making glass is sand , silica which is an oxide of silicon. Various other substances such as sodium carbonate calciom oxide , aluminium oxide are used depending on the physical properties required. They are amorphous, non crystaline and generally considered as super cooled liquids rather than solids.


GLUCOSE

This is the simplest sugar  having the formula  C6H12O6


GLYCEROL (GLYCERINE)

a clear, colourless, honeylike, sweet-tasting liquid belonging to the alcohol family; molecular formula HOCH 2 CHOHCH 2 OH

                           H

  • HALOGEN

A group in the Periodic table which include fluorine (F), chlorine (Cl), bromine (Br),and iodine ...They have 7 valency electrons.


  • HARD WATER

This water does not form lather with soap.  It forms a scum of insoluble calcium soap. It is due to the presence of Calcium and Magnesium salts dissolved in water.

Sodium stearate (Soap)  +  Calcium ions    Calcium stearate ( soap scum)  + Sodium ions.

2 Na.C17H35COO- + Ca2+ → (C17H35COO)2Ca  +2 Na +

Although such water has a peculiar taste they are not much of a health hazard.  There are two kinds of hard water named as ‘temporary hard water and permanent hard water. 

     Temporary hardness.

This is caused by chemically  dissolving carbonates of   calcium or magnesium.  The reactions can be shown as here.

Carbon dioxide and other acidic gases in the air dissolves in water.  This gives H+ ions

CO2  (g)  +  H2O  (l)   ↔       H2CO3  (aq)     

H2CO3  (aq)             H+   +   CO3 2--

Hydrogen ions react with calcium carbonate

Ca CO3     +  2 H+     + CO2- -↔   Ca (HCO3)2

In boiling water the reaction goes backward.  

The biggest problem with temporary hard water is that they form a sediment inside boilers and kettles. Temporary hardness can be removed by boiling while permanent hardness require special treatment. 

          Permanent hardness

This  condition is caused by the sulphates and chlorides which do not decompose on heating. These can softened by by passing through special resins that absorb the calcium and magnesium ions replacing them with sodium ions.

  • HYDROGENATION

As the name suggests this is a process of adding Hydrogen to certain compounds. Changing oils to margarine is an example.

I

  • INORGANIC

As this is the opposite of organic please refer ‘Organic’.

  • INSOLUBLE

This is the opposite of soluble. Please refer ‘Soluble’.

  • INDICATOR

Litmus paper, pH paper , phenolphthalein, methyl orange etc. are common indicators used in chemistry.Universal indicator is a pH  (acid /  base)  indicator on a scale 1 to 14.  

pH

0 to 3

3 to 6

7

8 to 11

11 to 14

Group

Strong acid

Acidic

Neutral

alkaline

Strong alkali

There are many plant colours that may be used as indicators. Eg  Shoe flower juice, Beet root turmeric are a few of them

  • IONIZATION ENERGY

The energy required to remove an electron from an atom. This may be given as for the first e- or for the other electrons. The unit usually is eV. or KJ / mol.

Ionization is the formation of ions from atoms.  This can happen in two ways; by getting an electron or by donating and electron. Two examples are shown here.
   Cl + e → Cl- When chlorine takes an electron Chloride ion is formed.
Na - e → Na+ When sodium atom sheds an electron it is converted to an ion.
Sodium ion having a plus charge can get attracted to a chloride ion to form sodium chloride.

This is the method of forming ionic compounds.
Ionization energy is the energy necessary to remove an electron from a neutral atom.

Ionization Energy for 1st electron.  (eV)

Name

eV


Lithium Li  

 35.

lllllllllllllll

Sodium Na  

 12

llllllllllll

Magnesium Mg

128

lllllllllllll

Aluminum Al

136

llllllllllllll

Potassium K

194

lllllllllllllllllll

Calcium Ca

206

lllllllllllllllllllll

Chromium Cr

247

lllllllllllllllllllllllll

Manganese Mn

25 7

llllllllllllllllllllllllll

Iron Fe

268

lllllllllllllllllllllllllll

Cobalt Co

278

llllllllllllllllllllllllllll

Nickel Ni  

288

lllllllllllllllllllllllllllll

Copper Cu

298

llllllllllllllllllllllllllllll

Zinc Zn  

30 9

lllllllllllllllllllllllllllllll

Gallium Ga

316

llllllllllllllllllllllllllllllll

Arsenic As

340

llllllllllllllllllllllllllllllllll

Strontium Sr

386

lllllllllllllllllllllllllllllllllllllll

Silver Ag

478

llllllllllllllllllllllllllllllllllllllllllllll

Cadmium Cd  

489

llllllllllllllllllllllllllllllllllllllllllllllll

Tin Sn  

507

lllllllllllllllllllllllllllllllllllllllllllllllllll

Platinum Pt

788

llllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll

Gold Au

79 9

llllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll

Mercury Hg

80 1

lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll

Lead Pb  

82 7

llllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll

Radium Ra

88 5

lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll

Actinium Ac  

89 5

llllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll


  • Fig. Ionization energy and Atomic numbers.

The graph shows the variation of this energy according to the atomic number.  As the proton number increases it becomes more difficult to remove an electron. When ever a new shell is added the elctron can slip away.

J

  • JADE

A valuable silicate containing calcium and magnesium. Used for carvings and ornaments.

                          K

  • KETONE
 A class of organic compounds  characterized by a carbonyl group attached to two carbon atoms.  eg  acetone.

Comments