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This phenomena depends upon the what is tested. iodine test usually gives a positive result of blue color for starch. The blue color is caused by the trapping of the iodine inside the structure of the starch (note that starch is a polyssacharide that has a helical structure). It is only with starch that this happens cause starch has the only one with a helical structure.
Now your question is why is it that the color disappears when heated, right?
This is because the heat causes an unwinding of the helical structure of starch releasing the trapped iodine making the solution colorless. However, if cooled, with no heat present, the starch structure becomes helical once more trapping the iodine returning the blue colored solution.
this is just what i learned from my Biochemistry class, hope it helps!!
Wiki User
∙ 11y ago
Wiki User
∙ 12y agoThe colour of iodine molecule I2 is due to n-> sigma anti bonding electronic transition. It changes its colour when it is adsorbed on starch or reduced to I-
Wiki User
∙ 12y agobecause of the iodine dissolved in an aqueous solution of potassium iodide then reacts with starch then producing a dark purple-black color.
Wiki User
∙ 12y agoIodine changes color when I contact with starch
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∙ 12y agoBlue-Black
Wiki User
∙ 11y agoBlack
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Why does starch turn blue with iodine?
the iodine does not turn the starch black."The iodine clock reaction is based around the colour change that occurs when iodine reacts with starch, turning from a clear colour to a black-blue colour." (2) The starch allows the iodine and the iodide ions to bond, forming a triodide ion.I2(aq) + I−(aq) ⇌ I3−(aq)In this reaction, iodide is viewed as a base, and iodine is viewed as an acid.The iodine is a ligand and is surrounded by the starch,as for the colour change, that is due to the iodine absorbing all light wavelengths corresponding to colours, hence not letting any through, so what you are seeing when the solution is black, is the absence of light and colour alltogether,hope that helps
What is the product of the reaction between starch and iodine?
There is a dark blue colour when iodine is added to starch instead of a yellow sort of colour when iodine is added to a substance without starch.
Why does iodine turn food blue?
I did this experiment at my middle school and any food that turns blue has carbohydrates in it. Ifi t doesn't change colour then it has no carbohydrates.
What color is starch with iodine solution?
it is a yellowish/orange colour but when iodine is present, than it will turn an dark-blue/black colour
What happens when iodine is added to carrot?
The colour of the iodine will turn from yellowish brown to dark blue
Why does iodine change colour when starch is present?
The startch and iodine molecule interact- the electron energy levels are affected on the iodine enough to change the absorption spectrim and hence the color.
Why does powdered sugar turn black in iodine?
it does not turn blue when mixed with iodine. I don't think there is a colour change.
What colors does starch turn if there is a little amount present?
starch will not change its own colour but it can change the colour of iodine solution. iodine solution is originally brown. after adding starch, it will turn into dark blue.
What colour does iodine solution turn red litmus paper?
The color not change.
Would the iodine solution change colour when it is tested on a slice of bread?
negative
What colour changes where observed with each food tested with iodine?
It change from orange/brown colour to blue/black if starch is present
How does a solid iodine change when it is heated?
It gets further apart and turns into a pink purple colour
What colour change is seen when excess potassium iodine is reacted with chlorine?
blue to brownish black
Why does the leaf change colour with iodine?
It turns black because starch is present because its making it because of photsynthesis
Colour of iodine solid?
The color of solid iodine is a dark purple.
Why does starch turn blue with iodine?
the iodine does not turn the starch black."The iodine clock reaction is based around the colour change that occurs when iodine reacts with starch, turning from a clear colour to a black-blue colour." (2) The starch allows the iodine and the iodide ions to bond, forming a triodide ion.I2(aq) + I−(aq) ⇌ I3−(aq)In this reaction, iodide is viewed as a base, and iodine is viewed as an acid.The iodine is a ligand and is surrounded by the starch,as for the colour change, that is due to the iodine absorbing all light wavelengths corresponding to colours, hence not letting any through, so what you are seeing when the solution is black, is the absence of light and colour alltogether,hope that helps
What is yellow brown colour?
Iodine
