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Hibiscus Flowers as a natural indicator (1 Viewer)

velox

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Does anyone have any info on why/how hibiscus flowers are natural indicators?

I just wrote up this practical : "Perform a first-hand investigation to prepare and test a natural indicator" and was wondering if this discussion covered all the bases. My teacher is pretty tight when it comes to practicals.....

Discussion:

There were no errors in the investigation as there was no opportunity for them to arise. We were simply demonstrating that indicators can be made from a readily available substance with basic equipment. The experiment was valid as results across the class were very similar if not identical. Some results varied from the majority as the beakers may not have been clean in the first place thus the chemical residue slightly changing the colour of the final solution. Many of the acid-base indicators are made from pigments extracted from the leaves and flowers of plants. These leaves or flowers change colour depending on whether they are in an acidic or basic solution. They are often complex organic molecules that exist in at least two different coloured forms.

TIA
 
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april____

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Natural Indicators

I don't know about Hibiscus flowers...
However we did three different ones.
1. Beetroot
Equip: 220mL beaker, tripod, bunsen, fresh beetroot, test tube rack, reagant bottle and label, acid and alkaline solutions
Method: 1. Cut two or three slive of fresh unboiled beetroot. Put slice in a 200ml beaker that is half full of water. Boilf the water for 5 minutes. A dark red liquid should have formed. Allow the liquid to cool and pour ir off into the reagant bottle. Label it. 2. Record the indicator colours bu adding a little of the indicator to a) acid b) water c) alkali
2.Cabbage
Equip: 250ml beaker, methylated spirtis, red cabbage, stirring rod, reagnat bottle and label.
Method:1. cut the red cabbage leaf finely and place in a 250 ml beaker. add 100ml of hot water and label the bottle "red cabbage indicator." 2. record the indicator colours a) acid b) water c) alkali
3. Rose Petals
Have fun with this!
 

richz

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i think, correct me if im wrong. Anything can be an indicator if heated in water and it produces a colour solution.
 

xiao1985

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not any thing... an indicator needs to be a weak acid/base, having the conjugate pairs distinguishable in colour...
 

velox

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Exactly Xiao, as the the indicator will have two forms of it (i.e. two colours), the ion and the molecule (iirc, i should start studying more chem =/)

So........anyone know the answer to my question and/or if my discussion is ok/bad/crap/good etc?
 

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