1. Biscuit Investigation
D. Crowley, 2008

2. Biscuit Investigation
Saturday, April 15, 2017
Biscuit Investigation
Your task is to investigate why a Jaffa Cake is a ‘cake’ and a ginger nut biscuit is a biscuit
As you complete this experiment you need to think how you can identify how the two types of food can be classified, whilst making this test you can make this test a fair one, how you can be accurate and precise, and how you can ensure the results are reliable

3. Initial Questions
Initially you need to brainstorm what differences there are between a Jaffa Cake and a ginger nut biscuit
What are they made of
What textures do they have
Do they have layers
How are they made
What happens when the biscuits are wet / dry etc…
Think about what experiments you could do to highlight the difference between a cake and a biscuit

4. Importance
McVities recently proved that Jaffa Cakes are indeed cakes (they baked a huge Jaffa Cake to prove this)
The difference is important for tax reasons as: -
Cakes do not attract VAT
The alternative classification would be a chocolate covered biscuit which is classed as a luxury food item, attracting VAT

5. Key Words
During your investigation you will come across some key words: -
Accurate: a measurement that is close to the true value (accuracy can be increased by controlling the key variables)
Precision: this is a more precise measurement, which can be achieved by using a smaller scale
Reliability: the experiment needs to be repeatable – if someone else did the experiment then they should get exactly the same results: this comes from repeating your experiment

6. Key Words
During your investigation you will come across some key words: -
Dependent variable – what is changed by the experiment (what you are going to measure)
Independent variable – what you change
Control variable(s) – what you are going to keep the same, making the experiment more accurate

7. Demo
Look at the two biscuits closely – what experiments are possible to identify the differences between a cake and a biscuit
Determine which factor(s) you could test for - what is your independent variable (what you change), and what is your dependent variable (changed by the experiment)
What control variables will you have to monitor?

8. Introduction
Initially write you introduction for the biscuit investigation
Note your aim (what we are doing); why we are doing it and what tests which will carry out and why
What makes a Jaffa Cake a cake, and not a biscuit: –
How moist is the cake
Is it layered
How hard / soft is it
How much air is within it
What are they made of
What textures do they have
Do they have layers
How are they made
What happens when the biscuits are wet / dry…

9. Stale
The difference which McVities used to prove that Jaffa Cakes are indeed cakes is that:-
Cakes go hard when they are stale
Biscuits go soft when they are stale
Jaffa Cakes go hard, therefore McVities successfully claimed that they are cakes (they baked a huge Jaffa cake to prove the point)
Why is there a difference between a cake and biscuit – what causes one to go hard when stale, and the other to go soft?

10. Moisture Moisture loss / gain is the difference: –
A biscuit goes hard when stale, as it is losing moisture from within the biscuit
A cake goes soft when stale, as it is gaining moisture from the surroundings
Your task is to therefore devise an experiment to prove that the difference between a cake and a biscuit is due to the ability to gain or lose moisture

11. Method
Your task is to now consider what methods you are going to use to measure the moisture changes between a biscuit and a cake
How are you going to make your experiment: -
Accurate (as close to the true value as possible)
Reliable (so someone else can repeat this experiment and get similar results)
Precise (how many readings are going to be taken and how can you ensure each repeat is completed in the same way)
Complete a step-by-step guide to completing your experiment
Note your independent variable (thing you change) and how you will change this; and your dependent variable(s), and how you will measure this
What data are you collecting / recording

12. Method - Moisture
In order to measure moisture variations we could do a variety of experiments: -
Using a moisture sensor identify the levels of moisture in the biscuit and the cake over time
Measure how ‘crumbly’ the biscuit and cake are over time
Measure the mass of the biscuit and cake, and then measure their mass after a given amount of time

13. Prediction
What do you expect will happen when you change the independent variable
Can you explain what will happen, and why you think this
E.g. I think that when I change the… the… will… because…
We should find a difference in both the absorbency and strength of the different brands of paper towel
This difference will probably be due to the different composition of each paper towel (what it is made from); how thick each sheet is; how the sheet is actually constructed etc…

14. Apparatus Order Form
Finally, you will need to order all the apparatus your require to carry out this experiment
Ensure you have thought of everything, and just as importantly you must identify how much equipment you need – e.g. 1 x scales; 3x biscuits etc…
Your apparatus form must be signed off before it will be given to the laboratory technicians

15. Mass Of Food (g) Over Time Overall Mass Increase / Decrease
Results - Moisture
Food
Mass Of Food (g) Over Time
Day 1
(Original Mass)
Day 2
Day 3
Overall Mass Increase / Decrease
Jaffa Cake
Ginger Nuts

16. Experiment
You have the first 20 minutes of the next 3 lessons to complete your experiment
Remember to be as accurate and precise as possible when collecting your results
The whole class will be carrying out the same experiment, so repeats will not be necessary for the biscuits

17. *Mini Task
Once you have set up your experiment you have a mini-assignment to complete: -
Using the nutritional information given you need to design a poster explaining to someone in the street which is the ‘healthiest’ choice to eat between the Jaffa Cake and the ginger nut
You will have the remainder of this lesson, plus the remainder of the next lesson (once you have collected your day 2 results) to complete this poster

18. *Jaffa Cake – Nutritional Information

19. *Ginger Nut – Nutritional Information

20. Conclusion
Your task is to graph your results for the change in mass over time of the Jaffa Cake and the ginger nut
A scatter graph is most suitable – time on the x axis, and mass of the biscuit on the y axis
Remember to add a title; units etc…
Once you have drawn your graphs you need to complete an analysis – what do the results show you / why do you think this is?

21. Graph
Hopefully you have found the mass of the Jaffa Cake decreased (as it becomes hard when it goes stale); and the mass of the ginger nut increased (as it becomes soft when it goes stale)

22. Evaluation
Finally you need to complete an evaluation – were there any anomalous results?
What errors may have caused these: -
Random error (happens occasionally)
Systematic error (same mistake occurred every time (likely due to you measuring this incorrectly)
How accurate was your experiment – did you consistently get the same results?
Was your method fair allowing you to collect accurate results?
Do you have enough reliable evidence to support the conclusion that you have made
What improvements would you do if you could repeat this experiment?

23. History
Marie Antoinette was beheaded during the French revolution - a period of time when most people had very little to eat
Marie Antoinette is supposed to have told the starving rebelling masses of people that, if they can’t eat bread they should, ‘eat cake’
Use what you have found out about ‘cake’ and ‘biscuit’ to comment scientifically on what Marie Antoinette said
Cake and bread both go hard when they are stale – so bread could be classified as a cake (so the starving rebelling masses were already searching for cake)!