A blank nine-step write-up with the correct table headings. Print it for a real lesson and fill it in by hand. See the specimen lab book
Blank write-up: Food tests
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Study Hack Lab
RP 4 · Biology
Food tests
Write-up template
Name
Date
Course
GCSE Biology
Board and specification
AQA GCSE Biology (8461), 4.2.2.1AQA GCSE Combined Science: Trilogy (8464), 4.2.2.1Apparatus and techniques: AT 2, AT 8
Class and teacher
Aim
Use qualitative reagents to test foods for starch, reducing sugars, protein and lipids. Then compare each food’s Benedict’s colour with a series of glucose standards to estimate how much reducing sugar it contains.
Contents
Plan and risk assessment
Apparatus
Method
Results
Graph
Analysis
Conclusion and evaluation
Make safe and clear up
A blank write-up for use in a real lesson. The headings follow the AQA required practical; the readings are yours to take. Layout v1, practical v2. Original material; not affiliated with AQA, which has not reviewed it.
1 Plan and risk assessment
Each reagent detects one kind of nutrient. Iodine solution turns blue-black with starch. Biuret reagent turns lilac with protein. Sudan III stains lipid red, and the stained oil floats as a layer. Benedict’s turns from blue through green, yellow and orange to brick red with reducing sugars, but only when heated: more sugar, further along.
Reducing sugar + Benedict’s (blue) → brick-red precipitate, when heated
Variables
Independent (you change)
Dependent (you measure)
Control (you keep the same)
Prediction
Table sugar is sucrose. A sucrose solution is heated with Benedict’s solution. What colour will it be?
Iodine solution is dropped onto starch solution and onto distilled water on a spotting tile. What will you see?
Biuret reagent is added to egg albumin solution, a protein. What colour will it be?
Risk assessment
Hazard
Harm it could cause
Control
2 Apparatus
Safety goggles Protect your eyes from the reagents and hot liquid.
Three foods to test The class’s foods, labelled A, B and C.
Pestle and mortar, distilled water and a stirring rod Grind each solid food and stir it with water, so some of it dissolves.
Filter funnel, filter paper and small beakers Filter the ground food to get as clear a solution as possible.
Known solutions: starch, egg albumin, cooking oil, glucose standards (0.1–1.0 %) and sucrose Positive controls, to see what each positive result looks like, and the glucose colour series.
Iodine solution, biuret reagent, Sudan III stain and Benedict’s solution, in dropping bottles One reagent for each nutrient.
Teat pipettes, labelled Move each solution and reagent without mixing them.
Spotting tile Small wells for the iodine test.
Test tubes in a rack For the biuret and Sudan III tests.
Test tubes in a second rack, labelled For the Benedict’s tests.
Water bath: a 1 dm³ beaker of water on a tripod and gauze, with a thermometer (resolution 1 °C) Heats every Benedict’s tube to the same temperature, about 80 °C; the thermometer checks it.
Bunsen burner, tripod, gauze, heatproof mat and test-tube holder Heat the water bath; the holder lifts hot tubes.
White tile Held behind the tubes so their colours are easy to judge.
3 Method
Write numbered steps someone else could follow. Say what you measure, with which instrument, and how you keep it a fair test.
4 Results
The table is drawn before you measure. Record each reading to the resolution of the instrument, then work out the mean of your repeats, leaving out any anomaly.
Iodine, biuret and Sudan III tests · Solid foods ground and filtered.
Solution
Colour with iodine solution
Colour with biuret reagent
Sudan III result
Positive controls: starch; egg albumin; oil
Distilled water (control)
Apple juice
Cheese
Bread
The water bath
Reading
Temperature of the water bath in °C
Before the Benedict’s tubes go in
Benedict’s test: glucose standards and sucrose · Heated in the water bath for 5 minutes.
Solution
Concentration of glucose in %
Colour after heating
Distilled water (control)
Glucose solution
Glucose solution
Glucose solution
Glucose solution
1 % sucrose solution
Benedict’s test: foods · Heated in the water bath for 5 minutes.
Food
Colour after heating
Apple juice
Cheese
Bread
Anomalies
Ring any anomalous result. Say what probably went wrong and whether you repeated it.
5 Graph
This practical has no graph: summarise your results in a sentence.
6 Analysis
Which nutrient tests gave a positive result?
Answer
7 Conclusion and evaluation
Conclusion
Conclusion: what do your results show? Use your own numbers.
Sources of error
For each, say whether it is systematic or random, and how it affected your results.
Judging colours by eye
Benedict’s not heated, or not heated for long enough
Heating the tubes straight in a Bunsen flame
One pipette used for every solution
The wrong amount of reagent
A cloudy (unfiltered) food solution
Reading the Sudan III tubes straight after shaking
A tube put into the water bath late (or taken out early)
Colours judged against the dark bench, with no white tile behind the tubes
Improvement
How could you improve the method? Say why it would help.
8 Make safe and clear up
Turn off the Bunsen at the gas tap. The tripod and gauze stay hot for a while
Lift the hot tubes out with a test-tube holder and leave them in the rack to cool
Pour the solutions down the sink with plenty of water