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Chemicals.

posted Jan 28, 2015, 5:55 PM by Ranmini Perera   [ updated Dec 1, 2015, 3:38 PM by Upali Salpadoru ]

Collecting Chemicals



Fig.1 Ali heating  a copper wire fixed to a piece of wood.

Note Note the precautions he had taken.

Looking at chemicals, touching them,(only if harmless) smelling them and mixing them can be an exhilarating experience for boys and girls. 

But there is a  code of conduct, that has strictly to be followed:.


They are as follows:- 

  • You have to be over 12 years to start collecting chemicals.
  • Always  get an adult to help you especially if you are below 15 years.
  • Use only safe chemicals .
  • Never play with chemicals.
  • Never mix at random. Follow instructions carefully.
  • Leave room for spurting and mild explosions.
  • Wear gloves and goggles when ever possible.
  • Wash your hands with soap and water after touching chemicals.
  • TEST

    What happens ?

    <!--[if !supportLists]-->1.        <!--[endif]-->Attached a copper wire to a stick and heated  by a non luminous flame of the gas cooker.

     

    Change of colour in wire…………..

    Did it melt?................

    Change of colour of flame………………..

    Colour of wire after cooling………………..

        2. Added to water.

    Did it sink?

    Was there a change after a week?

    Does it rust or corrode?

        3.  Kept in vinegar for a week,(vinegar is an acidic solution)

    Was there a change in glitter(shine) ?

    Was there a colour change?

In the same way you can study the other metals too. Some examples of metals and non metals are given here.
         Chemicals


  • SOME EASILY OBTAINABLE NON­-METALS

    Non - Metal

    Description

    From where  to get?

    Carbon

    (Aguru)

         C

    Usually a black solid present in many forms.

    A crystalline colourless form exists as Diamonds

    Lamp black (soot) Char coal,  Coal., graphite

    .

    Sulphur

    (Gendagam)

     

    A yellow solid

         S

     


    Very common May be obtained from Ayurvedic drug stores. gardeners

    WARNING

    The gas comes out when sulphur burns is poisonous. If you wish to burn this it has to be done outdoors.

    Iodine

     

    Dark purple crystals.

             I



     

     

    Available in pharmacies as tincture of iodine.

    (This a solution in alcohol)

     Most of the other non metallic elements are either gases , such as Oxygen, Hydrogen, and Chlorine or far too dangerous to keep such as Phosphorus

    WARNING

    • The test tube must be moved up and down so that heating will not be only at the bottom.
    • STOP heating when sulfur melts.
    • The mouth of the test tube must be directed away from you so that nothing from any spurt will  come to you.
    • On cooling sulphur will adhere to the test tube. It must be removed by melting.

Now Nelly wants to know, what exactly is a chemical substance. ‘A chemical’ may be defined as a substance that will maintain the same consistency. All chemicals are divided into two main groups, Elements and Compounds. Let us pay some  attention  to ELEMENTS first.

Fig Nelly heating sulphur in a test tube  ( Not drawn to proportion)

There are only about one hundred and eighteen  elements in the entire Universe
. These can be divided into ‘Metals’ and ‘Non-metals'

FEW EASILY OBTAINABLE METALS

  • Know the Metal

    Description

     

    From where  to get?

     

    Copper

     

    Orange solid

      Cu



     

     

    From old electrical wires.

    Gold

      Au

    Yellow solid.

    Has a permanent glitter.

    Your chains, bangles etc. (Too precious to play with)

    Silver

     

    A photo of a nugget

      Ag

    <!--[if !vml]-->


     

     

    Glitter fades slightly, Used in jewelery.

    Aluminium         

      Al

    Silver solid.  Fairly light.

    Glitter fades under certain conditions.

    Chocolate wrappers and some cooking foil etc/

    Iron

      Fe

    Silver solid

    Glitter is short lived..

    Rusted tin cans and nails which have to be cleaned with sand paper.

    Magnesium 

      Mg

     

    Silver solid fairly light.

    Glitter fades.

    Chemical suppliers.

    Lead

    Sin.)

       Pb

     

    Greyish silver

    A heavy metal

    Present in solder.

    WARNING

    Lead vapour is a dangerous poison

    Mercury

       Hg

    Silver coloured liquid.

    Very heavy.

    Mercury can go into other metals and spoil them

    Present in many instruments like thermometers. but difficult to get. 

    WARNINGShould never be spilled as the vapour  arising from tiny drops is really harmful.

Chemical compounds

Fig, 3 The difference between Elements and Compounds.

Let us start with a very common chemical compound which you can obtain from a chemist or garden centre. Gardeners use this chemical as a fungicide. This you may get as a blue powder or blue crystals. Copper, as you may know is an orange coloured metal. Do you know why they call this blue non metallic substance ‘copper sulphate’?
We can establish the accuracy of this nomenclature by a simple experiment.

Experiment

Aim:   To justify the name of copper sulphate.  


Fig. 4  Keeping a piece of  Iron nail in a solution of copper sulphate.

Method
Take two similar pieces of iron, such as nails or clips. Make a solution of copper sulphate using a previously boiled water. (Boiling removes the dissolved gases in the water.) Immerse  the nail in the solution and leave it for a few hours. 


Observation
Nelly observed a brown and coloured deposit on the silver coloured mail.. The colour of the solution was then more greenish than blue.


Reason
Iron can displace copper from the compound copper sulphate. This rxperiment shows that there is copper in copper sulphate.

 

Water is another Compound

 

In this illustration, atoms are represented as babies. Molecules are compared to groups of babies holding hands. One molecule of Oxygen joins with two molecules of Hydrogen to form two molecules of Water. This is what happens when Hydrogen burns.

ALI'S Collection of Solid Chemicals 

  

Chemical

Formula &Colour

                   Action with water

 

 

Soluble or Insoluble

Colour of solution

1. Salt -

Sodium chloride

NaCl

Colourless crystals

Soluble

Colourless.

2. Burnt lime

Calcium oxide

CaO  *

White

 

 

3. Condys

Potassium permanganate

KMnO4

Dark purple

 

 

4.Baking soda

Sodium hydrogen carbonate.

NaHCO3

 

 

 

5. Caustic soda

Sodium hydroxide

NaOH **

 

 

 *    If the chemical is fresh, water may boil and spurt out.

**  Can harm the tender skin.

 chalaka 


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