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What do you want to know about bleaching?

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 There are many things one can do with bleaches. As a bleach is a chemical substance by itself, many things and experiments can be done by just using household bleach.

All this is possible due to the chemical properties of bleach.

Here are some experiments one can conduct using bleaches.

 

Galvanized Tacks, Drugstore Iodine, and Household Bleach

Materials

1. Galvanized Tacks

2. Iodine

3. Glass cups

4. Liquid household bleach

5. Vinegar

Procedure

  1. Cover the bottom of a glass with a layer of small, galvanized tacks that are coated with a layer of zinc.
  2. Add some tincture of iodine to the glass. Use just enough to cover the topmost tacks.

    3. The iodine solution covering the tacks now has the very dark, purple violet colour of the elemental iodine itself. But if you leave the solution for about half an hour, you will see the liquid slowly fading to a pale yellow or losing its colour completely.

  3. Carefully pour the solution itself into another glass, leaving the tacks behind.
  4. Now add a few drops of liquid household bleach into the pale solution.

    5. à Immediately the very dark purple of the iodine returns.

  5. If the colour appears to form clumps, producing a lumpy appearance within the liquid, add a few drops of vinegar.

à The vinegar causes the lumps to dissolve, producing a dark solution which looks very much like the iodine solution.

Explanation:

Both the loss of colour from the iodine solution and the regeneration of the original colour take place due to a redox reaction. In reducing the purple iodine to colourless iodide ions, the zinc metal acts as a reducing agent and transfers its electrons to iodine molecules.

I2+ Znà Zn2+ + 2I-

In restoring the colour, the solution of bleach, which contains a reserve of ClO-, oxidises the colourless iodide ions back to purple iodine molecules.

The clumps that form appears because hydroxide ions of the basic liquid bleach react with zinc ions to produce insoluble zinc hydroxide, which isn’t soluble in water. The acetic acid of the added vinegar reverses the process:

Zn(OH)2+ 2CH3CO2Hà Zn2++ 2CH3CO2- +2H2O

 

Vitamin C, Drugstore Iodine, and Household Bleach

Materials: A glass jar

                     Galvanized tacks

                     Iodine solution

                     Household bleach

  1. Place a drop or two of drugstore iodine on a piece of cotton cloth. If this is an article of value, you might consider it ruined.
  2. However you can remove the stain by rubbing it with a moist tablet of vitamin C. Dampen the tablet with a little water and rub it over the surface of the stain. The colour of iodine disappears!!!

Explanation:

It might seem to be magic but it is actually redox in action again. Vitamin C is an organic compound, which can be oxidised easily, and so makes a good reducing agent. The redox reaction converts the I2 into colourless I-, just like the first experiment with the household bleach. Vitamin C is used as a sacrificial antioxidant in protecting some foods against oxidation. It acts much like zinc and other metals with reducing properties.

This example of everyday chemistry works well for removing iodine stains from clothing and similar articles using household bleaches. But be careful not to touch the fabric until you rinse out the residual I-. The bleach can reoxidise any remaining I- to I2. It is best to rinse the area thoroughly immediately after the stain is removed.

Dissolving Fibers

Materials:

A small lump of hair

Household liquid bleach

Small glass jar

Teaspoon

Procedure:

  1. Collect a small sample of hair from a local beauty or barber salon and place the hair in the jar. Roll the hair into a small ball.
  2. Fill the jar ¼ full with bleach.
  3. Use the spoon to push the hair down into the bleach so that the fibers become wet.
  4. Allow the jar to stand undisturbed for about 20 minutes.

Results:

Foam forms on the surface of the bleach and small bubbles are seen on the hair. The hair is partially or completely dissolved!

Explanation

Bleach is a basic chemical and hair in an acid. The neutralisation reaction between an acid and a base produces a salt and water. Since bleach can dissolve any fiber that has acidic properties, it is used on cotton because cotton is basic. However, it will dissolve acidic wool due to neutralisation.

Webpage by Team 27034

Last modified: 4/7/99

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