Step-by-step methods, safety and results for starch, reducing sugar, non-reducing sugar, protein and fat tests — and how to record them.
4 narrated scenes. Press play, listen and read along — the points appear as they are explained. Use ‹ Prev / Next › or the scene bar to jump to any scene.
Five tests, five colour changes. Get the method and the recording right and this practical is free marks.
Narration uses your device’s built-in voice. No sound? Switch to “Captions only” — the captions advance on their own.
Copy these into your notebook in your own words — that is how they stick.
Iodine: brown → blue-black.
Benedict’s + heat (water bath): blue → brick-red.
Boil with HCl, neutralise with NaHCO₃, then Benedict’s.
Biuret (NaOH + CuSO₄): blue → violet.
Ethanol emulsion → cloudy white; grease spot → translucent.
Goggles (NaOH, HCl); water bath for heating; ethanol away from flames.
The kind of support a teacher gives after the lesson: worked examples to attempt first, a board illustration, key terms, common misconceptions and memory aids.
Try it in your notebook first, then reveal the solution one step at a time.
Try it in your notebook first, then reveal the solution one step at a time.
| Test | Negative | Positive |
|---|---|---|
| Iodine (starch) | Yellow-brown | Blue-black |
| Benedict’s, heated (reducing sugar) | Blue | Green / yellow / orange / brick-red |
| Acid hydrolysis then Benedict’s (non-reducing sugar) | Blue | Brick-red |
| Biuret (protein) | Blue | Purple / violet |
| Ethanol emulsion (fat) | Clear | Cloudy white emulsion |
Examiners expect the colour words below — learn them exactly.
Benedict’s rainbow: Blue, Green, Yellow, Orange, Red — “Big Green Yams Often Ripen”.
Food technologists in Caribbean food and beverage companies test products for sugar and protein to make sure the nutrition labels are accurate.
List five foods eaten at home. For each, predict which of the four food tests would be positive. Check your predictions in your next practical.
3 quick games on this lesson. Earn XP and badges as you play — your best score for each game is saved. Games are for practice and do not change your exam readiness.
6 items modelled on real CSEC Paper 1 questions. Choose one answer for each, then check. Aim for 80% or better.
Write full answers, then reveal the mark scheme and tick the points you earned (10 marks in total). Your answers are saved on this device.
Question 1 [10 marks]
You are given three unlabelled solutions: egg white, glucose and sucrose.
(a) Describe how you would identify each. [6]
(b) Draw up a results table (describe the columns) and state TWO precautions. [4]
Everything in this lesson is based on these parts of the CXC syllabus and papers.