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    1 Test For Starch

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    FardeenKhan
    This document describes an experiment to test for the presence of starch using iodine solution. Four test tubes were prepared with glucose solution, starch solution, albumen solution, and water. Iodine solution was added to each test tube. Only the tube with starch solution developed a blue color, indicating a reaction between starch and iodine. The purpose was to demonstrate that iodine can be used to detect the presence of starch but not glucose or albumen.

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    1 Test For Starch

    Uploaded by

    FardeenKhan
    408 views4 pages
    This document describes an experiment to test for the presence of starch using iodine solution. Four test tubes were prepared with glucose solution, starch solution, albumen solution, and water. Iodine solution was added to each test tube. Only the tube with starch solution developed a blue color, indicating a reaction between starch and iodine. The purpose was to demonstrate that iodine can be used to detect the presence of starch but not glucose or albumen.

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    1 Test for starch

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    This document describes an experiment to test for the presence of starch using iodine solution. Four test tubes were prepared with glucose solution, starch solution, albumen solution, and water. Iodine solution was added to each test tube. Only the tube with starch solution developed a blue color, indicating a reaction between starch and iodine. The purpose was to demonstrate that iodine can be used to detect the presence of starch but not glucose or albumen.

    Copyright:

    Attribution Non-Commercial (BY-NC)
    Download as DOC, PDF, TXT or read online from Scribd
    Download as doc, pdf, or txt
    408 views4 pages

    1 Test For Starch

    Uploaded by

    FardeenKhan
    This document describes an experiment to test for the presence of starch using iodine solution. Four test tubes were prepared with glucose solution, starch solution, albumen solution, and water. Iodine solution was added to each test tube. Only the tube with starch solution developed a blue color, indicating a reaction between starch and iodine. The purpose was to demonstrate that iodine can be used to detect the presence of starch but not glucose or albumen.

    Copyright:

    Attribution Non-Commercial (BY-NC)
    Download as DOC, PDF, TXT or read online from Scribd
    Download as doc, pdf, or txt
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    Glucose, starch and albumen were tested to see their reaction with iodine. Starch was expected to turn blue with iodine while glucose and albumen were not expected to change color.

    Glucose, starch and albumen were tested. Only starch was expected to produce a color change (blue) with iodine.

    A single set of results is not enough to make broad generalizations. More samples of different sugars, proteins and fats would need to be tested.

    Starch test p.

    Experiment 1. The test for starch

    (a) Label four test-tubes 1-4.

    10% glucose solution into tube 1

    1% starch solution into tube 2


    (b) Put about 20 mm (depth) of
    1% albumen solution into tube 3

    water into tube 4

    (c) To each tube, using a dropping pipette, add three drops of iodine solution. Shake the tube
    (sideways, not up and down) to mix the contents. Look for any colour changes apart from the
    yellow colour of iodine itself. Copy the table below and record the results in your notebook.

    Substance Colour change after adding iodine

    10% glucose solution

    1% starch solution

    1% albumen solution
    water
    Starch test p.2
    Experiment 1. Discussion

    I The substances selected for testing are examples of three of the principle chemical substances
    in cells, sugar (glucose), starch, protein (albumen). With which of these substances did iodine
    react to give a colour change ?

    2 Does your result indicate that there is, for example, no sugar and no protein that will
    give a colour change with iodine ?

    3 What experiments would you have to carry out in order to give a confident answer to
    question 2 ?

    4 Does the result indicate that starch will always react with iodine solution to give a
    colour change?

    5 What was the point of the water in tube 4 ?


    Starch test p.3

    Experiment 1. Discussion - answers

    I Only the starch should give a blue colour. The glucose and albumen solutions may take up the
    colour of the iodine.

    2 The point is being made that the results from a single sample do not justify a sweeping
    generalization.

    3 One would have to test samples of all sugars, all proteins and all fats.

    4 The results permit confident prediction only about starch as a 1% aqueous solution.

    5 Students often say that the unreactive samples have 'turned yellow'. This control shows that the
    yellow colour is simply the diluted iodine.
    TEACHERS NOTES Starch test p.4

    Experiment 1. The test for starch - preparation

    Outline The experiment establishes that iodine gives a blue colour with starch, but not with
    glucose or albumen.

    Prior knowledge Use of test-tubes and dropping pipettes.

    Advance preparation and materials *

    10% glucose solution

    1% starch solution 10 cm3 per group

    1% albumen solution

    iodine solution 5 cm3 per group

    Apparatus-per group

    test-tube rack and 4 test-tubes


    4 labels or spirit marker
    dropping pipette (for iodine)

    * Instruction for preparing reagents are given on p. 01

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