Extended Essay: How do different Flavours, Storage Times affect the Effectiveness of Crisps as a Fuel?

Weigh all these samples on the top pan balance and mark their masses on a table.  

(Remember to weigh these without the zip lock bags)

3. Prepare second experiment of different storage temperatures:

Take out 15 Pringles Sour Cream and Onion crisps (I favoured using this flavour as

they are largest, so are easier to poke through).  Place each in a separate zip lock bag.  Mark a

bag with a temperature (25, 30, 50, 70 or 90’C) and test number (of 1, 2 or 3).  You should end

up with 3 samples with different test numbers for each temperature.

Weigh all of these samples on the balance again and note down their masses.

Put the 15 samples on petri dishes, marked again with their temperature and test

number, in an oven of their corresponding temperatures, for 5 hours, the experiment two (see

below) must be done right after taking them out.  (Note, for the 25’C, this is at room

temperature, so just leave it out of the oven.)

4. Finally, prepare the third experiment of different storage times:

Again take out 15 Pringles crisps, and place each in a separate zip lock bag.  With

the permanent marker, write down a time (2, 4, 6, 8 or 10 days) and a test number (1, 2 or 3)You

must have 3 samples with different test numbers for each storage time.

Once again, weigh out all these samples and note their masses.

For each sample, open them at different times so that each sample gets the right

period of exposure to air as it is assigned (e.g. 2 days).  Experiment Three must be done

immediately after.

Experiment One: What are energy values from burning

Different Flavours of Crisps?

1. Attach a Bunsen burner to a gas tap (make sure the gas cock is turned on).  Put the burner

on a heatproof mat.  Use the lighter and turn on the gas tap to start the Bunsen.

2. Use the 100ml measuring cylinder, pour in 100ml of tap water into each of the 2 copper

calorimeters.  Organize the rest of the set up to make calorimeters as shown in figure 1:  

Fig. 1. School Calorimeter

3. Put a crisp on each of the two mounting needles (make sure you remember what flavour and

4. what test number each is.)  Place them in the flame until they are ignited.

5. Hold each crisp between a copper calorimeter and a tin lid.  Let them burn until they

become all or mostly black.  If the flame goes out before this happens, try to ignite them

again.

6. After burning, read and note the final temperatures of the water.

7. Lastly, when the equipment cools down slightly, use paper towels to remove the metal

dishes.

8.  Weigh the metal dishes with their samples, then the metal dishes themselves.  Write down

both these values (these will help to calculate the final mass of the crisp sample.)

9. Remove water from the copper calorimeters and replace this with new 100ml of water each.  

If time allows, wash off any oil left on the tin lids and dry them before re-clamping to the

stand.  Assign two other samples of crisps to the two calorimeters.  Check and note initial

temperatures of water again.  Finally repeat steps 3-7 until all samples are burnt and

weighed.  After finishing this experiment do not disassemble the equipment yet.

Experiment 2: What energy values are given by burning

crisps Stored at Different Temperatures?

1. The two calorimeters should be set up and ready.  Assign two samples marked with

temperatures to these two calorimeters.  Note down initial temperatures of water in each

copper calorimeter.

2. Repeat steps 3 to 7 from experiment one, until all samples are tested.

Experiment 3: What Energy Values are given by burning

Crisps Stored at different Periods of Time?

1. Assign two samples with times marked to the two ready set up calorimeters.  Remember to

note down initial water temperatures of the copper calorimeters again.

2. Repeat steps 3 to 7 from experiment one until all samples are burnt.

Assumptions Made during the Experiment

Water was exactly 1 gram to 1 cm3, and always had a specific heat capacity of 4.18

kJ/kg/K.

All ashes and oil left on the tin lids were removed when weighing just the plate.

All different flavours of crisps would have the same effect on energy values as the

Pringles Sour Cream and Onion crisps, when exposed to different storage temperatures and

storage times.

Modifications of Original Plan

For storage times, I wanted to test different hours of air exposure: e.g. 2, 4, 6, 8, 10

hours.  But later decided an extra two hours may not have much of an effect on energy values,

so changed this to different days of exposure.  

Initially, I wanted to use a homemade calorimeter, see Fig. 2:

Fig. 2.  Homemade calorimeter

But this was very inconvenient to set up (neatly arranging the foil, sticking the paper

clip down.  Lighting the crisp with a candle often dripped wax over the crisp, which would

probably increase its energy value as wax is a fuel as well; but lighting with a match or splint

was difficult too, as I had to reach deep down the tin.)

Mass results were more inaccurate, as it was hard to pick up all bits of leftover ash

from the rough surface of the foil.

So, I used a calorimeter set up at school instead.  This was much more convenient

and accurate: burning quickly with a Bunsen instead of painfully reaching down with a match,

splint or candle; and weighing all ashes that fell on the tin lid instead of picking them up, then

easily scraping off almost all ashes from this plate to weigh the plate itself.

Qualitative Observations and Control Variables

Table 1.

Qualitative Observations

Table 2

Control Variables and How they are Controlled

Results

Notes:

See calculations of “% error of enthalpy change” and “enthalpy change” after the final graph

in this section (“Graph to show the different Enthalpy Changes (energy values) for the crisps’

different Storage Times”)

Error Bars are not drawn as they are relatively insignificant

Temperatures are measured initially in degrees Celsius, but later converted to Kelvins. 

What Energy Values will different Flavours

of crisps Give?

(Please see appendix for all raw data tables used to derive values in the following tables)

Table 3

Showing Enthalpy Changes (energy values) for Different Flavours of Crisps

Fig. 3. Here, it seems that the Calbee Curry flavoured crisp has the highest energy value, whilst

the Jack and Jill, and Edo brands have the lowest.

What are the Energy Values from crisps at

Different Storage Temperatures?

Table 4

Shows Enthalpy Changes (energy values) of Crisps at Different Storage Temperatures

Fig. 4. Graph showing Enthalpy Changes (energy values) for crisps at Different Storage

Temperatures

Apparently, there seems to be a general positive correlation of temperature and enthalpy change.  

However, after 70’C, the temperature drops rapidly.  Noticeably, this graph of

temperature against enthalpy change reminds me of the classic temperature against enzyme

activity graph shape.

What Energy Values are given off by crisps at different

Storage Times?

Table 5

Showing Enthalpy Changes (energy values) for Different Storage Times

Fig. 5.  Graph Showing Enthalpy Changes for different Storage Times

From the above graph, there seems to be a negative correlation between the storage time (amount

of time exposed to air) and enthalpy change (energy values).

Example Calculations

Note: all temperature and mass changes of crisps are calculated using averaged values (see tables

above.)

Enthalpy Change:

e.g. for investigating a crisp left exposed to light and oxygen for 2 days.

Enthalpy Change  =

Mass X Specific Heat Capacity X Change in Temperature 

      Change in Mass of Crisp

=   (100g) X (4.18) X (9.7)   = 4096 J/g

0.99

% Error in Enthalpy Change:

First, we have to know the accuracies (random uncertainties) of all apparatuses used for

measurements affecting enthalpy change: i.e. mass of crisp, volume (assumed to be mass) of

water, and temperature of water.  These factors were measured by the equipment below:

Table 6

Apparatus and their accuracies

Since the enthalpy change calculation required a change in mass and in temperature, the balance

and the thermometer must have been used twice, so their random uncertainties must be doubled.

Therefore,

Total of random uncertainties from apparatuses = 0.01 X 2 + 1 X 2 + 1 = 3.02

Taking the enthalpy change from a crisp exposed to light and oxygen for 10 days, 3213 J/g,

Total of random uncertainties from apparatuses  X 100

      Enthalpy Change calculated

=   3.02  X 100 = 0.094 % = 0.09%

3213

Conclusion

Brands/Flavours

From the results, we see that Calbee Curry has the highest energy value, whilst Edo

and the Jack and Jill had the lowest.  This may be due to Calbee Curry having the highest, Jack

and Jill and Edo the lowest fat content of all the flavours.  Unfortunately conclusion cannot be

verified as Calbee crisps do not provide sufficient nutrition information.

Storage Temperature

In investigating the effect of different storage temperatures, as temperature

increases, energy increases, but plummets at 70’C, strangely resembling a temperature against

enzyme activity graph.

In fact, this effect of temperature on energy values may be implicated with

glutathlone peroxidase.  This is an enzyme that “protects tissues from oxidative damage”

(Bender p168).  Oxidation results in the break down of lipids to fatty acids (as in rancidity, see

below), these nutrients then leak out of the crisp, lowering energy values.  Therefore, as the

temperature increases, oxidation prevention is more efficient as substrate molecules gain more

kinetic energy—fewer fatty acids will leak out, retaining a higher energy value.  Yet after 70’C,

the enzyme denatures, oxidative damage then increases dramatically, decreasing calorific values.  

However, there may be a major error here (see evaluation on “limitations”), so I may need to

recheck results with other flavours of crisps.

Storage Time

Finally, it seems that there is a negative correlation between the duration of storage

time and the energy value of crisps.  

A possible explanation is the loss of antioxidants over time, caused by reactions

initiated by light and oxygen (“Olive Oil”).  Antioxidants are a type of preservative that slow

down rancidity: a process where fat molecules are broken down by reacting with oxygen in the

air at room temperature (“Antioxidant”).  Lower energy values may be due to an increased

break down of fat molecules as the antioxidants are lost: free radicals of oxygen from rancidity

“destroy nutrients”, the fat-soluble vitamins and polyunsaturated fatty acids (Robinson p13).  

This ‘destroying of nutrients’ means these fatty acids and vitamins leak out of the food, thus their

nutritional as well as their calorific value is lost.  Thus to sum up, over time, antioxidants are

lost, resulting in less efficient retardation of fat molecule break down, where nutrients then leak

out and are lost.

Since many fats, including vegetable oil, contain naturally occurring antioxidants,

(Bender p23) the crisps very likely contain these preservatives too in their vegetable oil

(ingredient in food label).

Referring back to the research question, we find that crisps stored at about 70’C and

stored for the least amount of time (exposure to air), e.g. less than 1 day, will be the best

fuel—gives off most energy.

However, we have only assumed that the Pringles Sour Cream and Onion crisps’

results for storage temperature and storage time can generalize to all flavours of crisps.  

Therefore, the conclusion may not offer a very accurate trend for optimum storage temperature

and time conditions to provide the best fuel of crisps.

Looking at these findings, new questions are raised.  If crisps are to be used as bio

fuels in the future, we will have to consider their method of storage.  If possible, they should be

sealed up in air tight containers before using, and should be stored at around 70’C, which would

optimise the amount of energy given by the fuel.  However, to store them at a relatively high

temperature may be costly and energy consuming—why lose energy to produce energy?  Also,

we must remember that to be put to industrial use, bio fuels would have to produce a substantial

amount of energy, so the crisps would probably have to be burnt in huge groups in order to be

any use.  Therefore as a point for further investigation, the amount of energy used in the actual

manufacture of crisps should be studied, to ensure ourselves that they will serve as effective

biofuels—releasing enough energy to cover energy costs from producing the fuels themselves.

Evaluation

Now I will assess the effectiveness of my investigation to answer my research question.  First

of all, there are:

Limitations of the Procedure:

After burning, a noticeable amount of oil oozed out of the crisps, and was difficult to

remove from the metal dish — mass of metal dishes only would be higher than supposed.

There was possible heat loss from the copper calorimeter walls, as it is a thermal

conductor.  More heat loss could occur through the top of the calorimeter — final temperatures

of water would therefore be lower than they should be.

Furthermore, when burning, the flame often was aimed in random directions, not

touching the bottom of the copper calorimeter – the water’s final temperature may be lower than

it should be.

Even when the flame is clearly aimed at the bottom of the copper calorimeter at all

times, a large amount of heat is lost from under the calorimeter — again final temperature

readings of the water would result in lower values.

When exposing samples of crisps to air, noticeable amounts of oil oozed out of the

crisps — this may then lower initial masses taken of crisps.

In investigating different brands and flavours of crisps, the homemade calorimeter

was used, and candle wax dripped onto many of the samples — this may have increased energy

values, since the extra wax could act as extra fuelling material for the crisp.

Evaluation of investigation in answering the research question:

I acknowledge there are many errors and uncertainties in the results; however there are also

many successfully controlled variables (see Table 2 in “Experimental Method”) to standardize

results, some repeat experiments and a range of values tested that show some trends in the

graphs.  Thus I would suggest

Possible improvements for a future similar study:

Do more repeat experiments.  E.g. for all variables investigated, I could use 10 tests

for each brand/flavour, storage temperature and storage time, and take an average, rather than

only 3 tests.

Investigate an even broader range of each variable—for instance I could use 10

rather than just 5 different changes in the variable.  For storage temperatures, I could

experiment with 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100’C.  As for storage times, I could

investigate the effects after 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 days.  Finally I could test 10 different

brands/flavours instead of five   Doing this would show trends more clearly on the graphs.

The metal dish should be weighed before burning, rather than after, so it would

eliminate errors when removing leftover material.

A damp cloth could be used to wrap all around the copper calorimeter, only

exposing the thermometer.  The cloth would help insulate and reduce heat loss.

To stabilize the flame direction, I could use a fan to lightly blow the flame into

always touching the bottom of the calorimeter.  I could also ask a friend to help fan on the

opposite side of me to make sure the flame is directed to the middle.

The sample could be burnt in a tall tin can with the copper calorimeter and metal

dish inside, so less heat escapes from between the calorimeter and dish.

If I had time, I would have done all experiments on the school’s set-up calorimeter

than the homemade one, to avoid inaccuracies such as wax dripping on crisps.

Reliability of Secondary Sources

Facts on bio fuels:

A number of articles from the Global Newsbank may be less reliable, as they are only

newspapers, not professional scientific reports.  However, the Encyclopedia Britannica one has

more authority, so may be more reliable.

Enthalpy Change Theory:

Offered from my teacher’s lesson notes.  This should be quite a reliable source, as many

different textbooks, encyclopedias, books and Internet pages mention the same formula.

Oxidation theories:

With the exception of one professional website and a consumer magazine, all other sources here

should provide reliable information.  They are either books, from Encyclopedia Britannica, a

dictionary or a science magazine (New Scientist).

Cross referencing also shows that antioxidant definitions and descriptions of their function are all

the similar.

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Chemistry, Shatin College.  27 Feb. 2008.

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Myers, Richard. The Basics of Chemistry.  Westport, CT: Greenwood Press, 2003.

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