LB: Assumptions

LB: Assumptions

As per usual, there are assumptions made in this project.

1. Density of GRB is constant inside each GRB.
2.  Distribution of heat in water is even and the same amount of heat energy is conducted by the water in every experiment.
3. Movement of GRB within pot as they cook will not affect how fast they cook.*see above.
4. Cling wrap/plastic bags used in shaping the GRB/measuring them is insignificant to the results.
5. Impurities in Singaporean tap water ""
6. Cornflour used to dust the GRB "".

LB: Final Experiment Results

LB: Final Experiment Results

Date: 11 July 2012

Time: 4pm-7pm

Room temperature: 27°C

Weather: Sunny

For this final experiment, instead of slowly measuring each GRB's volume, I only measured 2 GRB and extrapolated the volume of other GRB from their mass, Also, instead of first setting the mass of a GRB, shaping it then calculating its surface area, I set the shape (volume and surface area) then recorded the mass to save time. 

Figure 1 shows that the density of almost all GRB decreased, possibly until lower than the water's density, hence floating. The time taken to float was proportional to an increase in size and the percentage change in density usually inversely so.

From figure 2, the variable with the strongest correlation to both time taken and change in density was surface area before cooking. It has a strong (near 1) positive correlation with time, making it very likely that if surface area is increased, time taken can be found to have increased proportionally.

Figure 3 is a graphical representation of the correlation factors, with a majority of points near the trend line in graphs representing variables with high correlation, figures 3.1 (correl:0.92) and 3.2 (correl:0.89), but not so in figure 3.3, with weakly correlating variables (correl:0.23). However, points in figure 3.2 are still further away than points in figure 3.1.


In conclusion, my hypothesis was that the higher the surface area to volume ratio of the GRB, the faster it would float, with the assumption that the process of cooking cause GRB to expand. This expansion decreased the density of GRB to lower than water, and a higher SA:V results in a faster rate of heat absorption by the GRB. Hence, the process of cooking is also faster, and the properties of cooked GRB, including expansion, would be exhibited faster as well.


My results do demonstrate a general decrease in density as well as an inverse relationship between surface area to volume ratio and time to floating, however, the relationship between surface area alone to floating time is actually stronger.


Edit 25/7: The completed report is now uploaded. 

LB: Final Experiment Procedure

LB: Final Experiment Procedure

Research Question: Does the process of gelatinisation cause the GBR to float?
Hypothesis: The higher the surface area to volume ratio, the faster the GBR floats in water.

Steps

1. Measure out 175g each of rice flour and water using a weighing scale, and mix until evenly distributed.

2. Take a small part and mix in green food colouring. Using the method outlined in this post, make a flat of 1 cm thickness.

I counted playing cards to make blocks of the correct height.

3.  Repeat step 2 4 times for 4 pieces of dough from 2-5 cm thickness, but with different colours of food colouring.

all the different colours of dough (fifth was a mix made from the scraps)

4.  Place all disks of dough onto plates, cover with cling wrap and place into a fridge to chill until the dough is hard and unyielding to the touch. This takes about two days. Then, take the disks out.

5. Letting the thickness of the disk be n, cut a cube with sides of n cm and a cuboid with sides of n by n/2 by 5/3n cm. For example, 1 cm thick disk would be cut into a 1 cm cube and a 1 by 0.5 by 1.7 cm cuboid. An exception is the 5cm cuboid, which will not be used as it does not fit into the displacement can.

After chilling, GRB cuts smoothly and does not stick to the knife

5.  Dust the GRB produced with cornflour.

Green 1 cm cube during dusting

from top to bottom, left to right: 5 and 3cm cubes,  3cm cuboid, 4 and
 2cm cubes, 2cm cuboid, 4cm cuboid, 1cm cube and 1cm cuboid

 6. Wrap the 3cm cube in cling wrap, gather the corners of the cling wrap and twist shut.

 7. Fill a displacement can with water, and slowly submerge the wrapped GRB while using the 100ml measuring cylinder to catch the displaced water. Record the volume and repeat steps 6-7 for the 4cm cube.

 8. Weigh and record the mass of each GRB.

Weighing the 4cm cube before cooking

 9. Using a 250ml cylinder, pour 1250ml of water  into a pot.* Put the pot on a hotplate set to 120°C and start the stopwatch. When the water has begun to boil, slowly drop all cuboid and the 1 cm cube GRB into the water by hand.

                                                                           Inserting the 1cm cube 

 10. Stir continuously with the strainer and record the time it took for each GRB to float. Turn off the hotplate when all GRBs are floating. 

Stirring with chopstick

All 5 GRBs in the second round are floating

 11. Switch the hotplate's settings to "keep warm" (70°C), and repeat step 7 (directly slipping the GRBs into the displacement can without wrapping them). Use hot water taken from the pot to fill the can.

Weighing the 4cm cuboid

12. Use the strainer to individually transfer each GRB to the scale or displacement can, then back into the pot and complete these two steps as fast as possible, before the GRB cools down.
13. Repeat steps 9-12 for the 5 GRB left.

At the end of first round, with 4 cubes cooked and rest uncooked

*Increased due to increased size of GRB, can observe sinking/floating better

LB: Trial 2 Results

LB: Trial 2 Results

Date: 30 June 2012

Time: 3pm-7pm

Room temperature: 27°C

Weather: Sunny

Trial 2 was conducted immediately after Trial 1 to check the repeatability of the results. From figure 3, the volume of the two 40g GRB was greater than their mass, but the opposite is true for the 20g GRB. Out of all the variables I identified initially, mass, volume, surface area or density do not predict the trend in time taken and only surface area to volume ratio is left.

LB: Trial 3 Results

LB: Trial 3 Results

Figure 4:  Photos used to derive values for surface area

Figure 1 uses image-j numbers

You'll notice that of the two methods, I've decided to take only image-j's values for surface area. This is because I think that taking data from different sources and treating it as one set of numbers will increase the difficulty of following these processes, as well as complicate identifying errors. Hence, only one method should be used at this stage, of trials.

As to why image-j was chosen over manual, it is more accurate in measuring areas in the 2D photo . The different radii in figure 2 indicate that the GRB are still not perfectly round, though the difference is smaller than in previous trials and this compromises the accuracy of the manual method. There is no need to find out the radius for calculating areas of spheres and besides I think it is more useful to measure the 2D photo well, since all the GRB are of the same thickness anyway.

Illogical Density 

In figure 1, the uncooked 20g flat is less dense than water, which shouldn't be considering it sank. There are a few other points of contention as well, such as 2/3 of the GRB getting significantly denser (but floating) after cooking. Discussion with my teacher (Ms Tan Beng Chiak) still concluded that this experiment hinged on accurate measurements; if I continue trying to improve experimental method, then ideally at the end I can obtain results that show the GRB getting less dense.

Surface Areas in Figure 2

If density can show how the GRB floats, then surface area is a possible reason as to why. In figure 2, the surface areas before cooking from the two methods are reasonably close, but the areas after cooking differ up to 10 cm². The reasons presented above for using image-j may still stand, but this large difference needs to be addressed in future experiments as well.

Surface Areas in Figure 3

Linked to the above issue, surface area doesn't seem to predict when the GRB will float, but it is possible to get more accurate measurements of surface area.

LB: Trial 3 Procedure

LB: Trial 3 Procedure

Research Question: Does the process of gelatinisation cause the GBR to float?
Hypothesis: The higher the surface area to volume ratio, the faster the GBR floats in water.

Steps

1. Measure out 60g each of rice flour and water using a weighing scale, add blue and yellow food colouring and mix until evenly distributed.

 2.  Divide the dough into 3 parts, 60g, 40g and 20g using a spring balance.

3.  Roll all parts into balls and dust with cornflour.

After rolling

l Flatten as illustrated in the other post.

4.  Lay all GRB on black paper covered with plastic, with a ruler in sight, and then take a photo from directly above.

This photo will be used for measuring surface area

5. Wrap the 20g flat in cling wrap, gather the corners of the cling wrap and twist shut.

With as little air space as possible

6. Fill a displacement can with water, and slowly submerge the wrapped GRB while using the 100ml measuring cylinder to catch the displaced water. Record the volume and repeat steps 5-6 for the other two GRB.
7. Using a 250ml cylinder, pour 750ml of water  into a pot. Put the pot on a hotplate set to 120°C and start the stopwatch. When the water has begun to boil, slowly drop all GRB into the water by hand.
 8. Stir continuously with the strainer and record the time it took for each GRB to float. Turn off the hotplate when all GRBs are floating. 

9. Using the strainer, transfer all GRB into a plate while making sure they are not sticking and leave them to cool for 30 minutes.

10. Repeat step 4.

GRB after cooking

11. Repeat steps 5-6, but directly slipping the GRBs into the displacement can without wrapping them.

12. Weigh each GRB with the spring balance again.

LB: How the measurements were derived

LB: How the measurements were derived

This is an explanation (using trial 1, before cooking as an example) of various techniques used to get the results. Some are self explanatory/simple enough to cover in the list of steps, and these are the rest, updated as experiments progress. Note: even though the example is trial 1, image-j was actually used until after trial 3.

1. Surface area- manual and image-j
2. Making of flats from trial 3 onwards
3. Weighing with spring balance
4. Correlation formula/Graphs

1. Surface area

I have used two ways, manually and with image-j software, to find the surface area of each GRB, though how successful each is has yet to be evaluated. In the list of steps, such a photograph was to be taken:

fom trial 1, before cooking, taken with camera held parallel from ground

Manual

Using powerpoint, a ruler and colour-coded squares encircling each GRB was superimposed onto the photograph. 

After the photo has been marked

The ruler from the original photo was to indicate the scale of the photo. The lines of the square extended until the ruler, where the diameter of each GRB is read off two times, length and width wise. Taking the average, surface area is calculated with the formulas πr² (circle) for the flats, and 4πr² (sphere) for the balls. 
Figure 1: Manual calculations for surface area before cooking, trial 1

	Radius before cooking/cm (rounded to 1 dp)
Type of GRB	Derived from length	Derived from width	Average	Surface area before cooking/ cm2 (rounded to 1 dp)
Green 40g flat	3	3.1	3.1	120.8
White 40g flat	2.7	2.9	2.8	98.5
Green 40g ball	2.4	2.5	2.5	78.5
White 40g ball	2	2.2	2.1	55.4
Green 20g ball	1.8	2.1	2	50.3
White 20g ball	1.6	1.6	1.6	32.2

Image-J

Image-J is a free, downloadable software capable of analysing images. This is the developer's website. After the photograph was opened in image-J, I used the set-scale function to declare the number of pixels in 1 cm by drawing to scale a 1 cm line on the ruler. Then, I used the free-hand drawing tool to trace the shape of each GRB and the measure function to analyse and convert into cm² how many pixels the GRB was.

Figure 2: Image-J calculations for surface area before cooking, trial 1

	Surface Area/ cm2 calculated by image-j
Type of GRB	Before cooking
Green 40g flat	32.205
White 40g flat	25.496
Green 40g ball	18.948
White 40g ball	13.867
Green 20g ball	12.027
White 20g ball	9.579

Conclusion

• Because it calculates 2D area, image-J is not applicable for the spherical GRB and there is a great difference between image-J values and manual values. So, I've decided to forgo image-j for future trials and only use the manual method.
• The "spheres" were not perfect spheres. Because of the pliability of the douch, they had no structural integrity and easily lost their shape. Hence, no more tests using round GRB after trial 1.  

2. Making of flats

After trial 1 and 2 measurements were analysed, I realised that using hands to shape the flats led to inconsistency in the shape. After talking with a friend (Zhi Rui), we came up with a way to improve that.

Diagram of the process

Before placing the spherical GRB in, the set-up is covered in cling wrap to prevent sticking.

The blocks are anything (e.g. bowls, cups, pieces of wood), but each set is identical in height and the plate has a flat bottom. This method will make the force applied more even.

3. Weighing with spring balance

Photo from real life

The GRB is placed in a plastic “pouch”, then the hook of the spring balance is forced through the top, leaving the pouch hanging. The measurement is then read off the spring balance and the mass of the plastic is assumed to be negligible.


4. Correlation formula/Graphs

Correlation was calculated with the =CORREL(array1,array2) function in excel, which uses  (pearson product-moment correlation coefficient) as the formula. This has been chosen because the data to be analysed mostly fits Pearson's assumptions that it has interval/ratio measurements, a linear relationship, minimal outliers and homoscedasticity (consistent variance along the trend line). 

example

The graphs for the final experiment are created using Apache OpenOffice instead of the previous Excel.

LB: Trial 2

LB: Trial 2 Procedure

Research Question: Does the process of gelatinisation cause the GBR to float?
Hypothesis: The higher the surface area to volume ratio, the faster the GBR floats in water.

Steps

   1. Measure out 50g each of rice flour and water using a weighing scale, add a drop of blue food colouring and mix until evenly distributed.

Dough after mixing

   2.  Divide the dough into 3 parts, 2 parts of 40g each using the scale and 1 part of 20g using a spring balance.

3.  Roll all parts into balls. Then, evenly flatten 1 of the 40g balls until about 1 cm thick, leaving the rest untouched. Dust the GRB with cornflour.

4.  Lay all GRB on black paper covered with plastic, with a ruler in sight, and then take a photo from directly above.

This photo will be used for measuring surface area 

5. Wrap the 20g ball in cling wrap and place it inside a plastic bag. Squeeze out remaining air before twisting the bag closed.
6. Fill a displacement can with water, and slowly submerge the plastic bag while using the 100ml measuring cylinder to catch the displaced water. Record the volume and repeat steps 5-6 for the other two GRB.
7. Using a 250ml cylinder, pour 750ml of water  into a pot. Put the pot on a hotplate set to 120°C and start the stopwatch. When the water has begun to boil, slowly drop all GRB into the water by hand.
 8. Stir continuously with the strainer and record the time it took for each GRB to float. Turn off the hotplate when all GRBs are floating.

At 5.04 minutes, just dropped in GRB

At 8.30 minutes, with 40g flat floating

At 9.52 minutes, with 40g flat and 20g ball floating

    9. Using the strainer, transfer all GRB into a plate while making sure they are not sticking and leave them to cool for 30 minutes.

GRBs from both trials

10. Repeat step 4. 

11. Repeat steps 5-6, but directly slipping the GRBs into the displacement can without wrapping them. 

Displacement can measuring 40g flat, with 100 cylinder catching the displaced water

12. Weigh each GRB with the spring balance again.