Lesson 10 ·Class 9 · Digestive System · Match Lab
Testing Foods
Four tests, four colour changes.
Match each test to the result that confirms the nutrient.
Matched 0/6
Free play — tap an item on the left, then its partner on the right; each link tells you why. Switch to when you're ready to test yourself.
Only Benedict's test needs heat, and only Benedict's gives a graded result rather than a single colour.
What this lesson covers
Challenges to clear
- Match every test to its result.
- Connect the tube of plain distilled water to the reason it is on the bench at all.
The task
Match each test to the result that confirms the nutrient.
What this lesson covers
- Iodine test for starch — Yellow-brown iodine turns blue-black (A striking, unmistakable colour change.)
- Benedict's test for reducing sugar — Blue solution turns green, then yellow, then brick red on heating (The more sugar present, the further the colour goes.)
- Biuret test for protein — Pale blue turns violet or purple (The reagent reacts with the peptide bonds.)
- Translucent spot test for fat — Paper becomes translucent and the mark does not dry away (A water mark disappears as it dries; a grease mark does not.)
- Testing distilled water alongside — A control, to show the reagent alone gives no positive result (Without it you cannot be sure the colour came from the food.)
- Why Benedict's test needs heating — The reaction does not proceed at room temperature (Which is why the tube must go into a water bath.)
Hint
Only Benedict's test needs heat, and only Benedict's gives a graded result rather than a single colour.