What should you use to test if a type of food has starch, sugar or fat?

For the starch test, we use a solution of iodine. If iodine is added to a solution where starch is present, the iodine goes from brown to black-blue, indicating a positive test rule. Here is a picture:

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For the reducing sugars test, we use Benedict's solution. Benedict's solution is composed of sodium carbonate #(Na_2CO_3)#, sodium citrate #(NaC_6H_7O_7)# and copper(II) sulfate pentahydrate #(CuSO_4*5H_2O)#.

When we add Benedict's solution to a solution, it can form many different colours. If no sugars are present, it will be blue. If there are a lot of sugars present, it will turn red. Here is a picture of the test:


To test for fats, we must use an ethanol #(C_2H_5OH)# solution. We add ethanol to a sample solution and shake it. After that, we must pour in some water. If a cloudy white emulsion appears, then the test is positive, and lipids (fats) are present. If nothing happens, then the test is negative, and no fats are present. Again, here is a picture of the test:

![https://www.toktol.com/notes/context/3389/biology/lipids/ethanol-emulsion-test-for-lipids]()

I hope this helps!