tests

Question 1

Benedict’s test

Answer 1

test for reducing sugars

(-): solution remains blue when no reducing sugar is present

(+): the greater the concentration, the more precipitate is formed, and the greater the color changes:
Blue → Green → Yellow → Orange → Brick red

Question 2

Starch-iodide test

Answer 2

test for starch

(-): mixture remains yellowish-orange when no starch is present (e.g. glucose)

(?): red color indicates presence of maltose

(+): blue-black color indicates presence of starch

Question 3

Ethanol emulsion test

Answer 3

test for lipids

(-): the resulting solution will remain transparent when no lipid (fat + oil) is present in the original material

(+): cloudy white suspension will form when lipid is present in the original material

Question 4

Biuret test

Answer 4

test for proteins

(-): mixture remains blue when no proteins are present

(+): mixture develops a violet/lilac color in the presence of proteins