diffusion of vegetable dye in water

8/12/2019 Diffusion of Vegetable Dye in Water

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Alejandro Ivn Navarro Villarreal

May 2014

IB candidate number 2106-0050

Biology HL Internal AssessmentLab Design practice

Practice #1


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Diffusion of artificial dye in water

INTRODUCTION

Among the most common processes in living things is diffusion1. Diffusion is the

movement of a substance (called the solute) from an area of high concentration to one of

low concentration (the solute is usually dissolved in a solvent)6. Diffusion speed depends

on many factors, like: size of the solute particle, concentration difference, distance of

diffusion, and temperature, among others1. It is this last factor that is very important; we

have probably noticed that dissolving instant coffee in hot water is faster than dissolving

cocoa in cold milk. Temperature could be interpreted as the amount of energy a particle

has; the more energy, the higher the temperature6. So, if a particle has high temperature,

or high energy, it will move and thus diffuse faster than a cold particle. The aim of this

practice is to prove this relationship between heat of solution and diffusion speed, to prove

that as temperature goes up, so does diffusion speed.

RESEARCH QUESTION

The research question for this experiment is: How does water temperature affect the

diffusion speed of a vegetable dye?

The hypothesis is as follows: The hotter the water is, the faster it will diffuse; the colder it

is, the slower it will diffuse. This is because at higher temperatures particles have more

energy and move faster, so the dye molecules will advance further down the container

much faster than in a cold environment where the particles dont move as much.

VARIABLES

Independent variable: Water temperature. This will be achieved using an incubator

and measured in C by an alcohol thermometer within the incubator.

Dependent variable: Rate of diffusion. This will be obtained using a stopwatch to

measure the time it takes the dye to reach the bottom.

Controlled variables:

Temperature of dye: If the dyes temperature is not constant, it will change

the results because it will diffuse faster or slower; this was controlled

keeping the dye in an area with a constant temperature (ambient

temperature) before and during the experiment.


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Ambient temperature: Ambient temperature can modify solvent and solute

temperature and so modify results. This was minimized by keeping the

room temperature at a constant value (in this case, 23 C).

Amount of dye: If we use different quantities of dye our measurements may

not stay the same because they will not appear to diffuse at the same rate;

this was controlled by using the same amount of dye (one drop from the

integrated dropper) in all repetitions.

Amount of water: If we use more or less water then diffusion rate will be

eschewed; it will take less time to diffuse in a little water than in a large

amount of water. This was controlled by using the same amount of water

(10 mL) in all repetitions.

Agitation of solution: If the solution is agitated or otherwise disturbed, it will

diffuse more rapidly because of the extra energy imparted; this was

controlled by keeping the experiment in a stable work place and moving the

solution around as little as possible, as will as letting the container with

newly poured water rest for a little while (5 minutes) before proceeding.

Composition of dye: If we change the dye we use (and thus the dye

composition), results will not be homogeneous and we will not be able to

conclude. This was kept under control by using the same dye for all

repetitions.

Change in water temperature: Water temperature decreases by virtue of

being in an environment with a different temperature; this will affect the

results, but it was minimized by keeping the water inside the incubator for

as long as possible.

MATERIALS

a) Aquatech 1/100 sec chronometer (+/- .01 sec) (1)

b) Kimax 10 mL graduated cylinder (+/-5%) (3)

c) Pyrex 250 mL beaker (+/-5%) (1)

d) Incubator. This device consists of a box with a grill for placing the material to be

used, a thermometer and a glass door. (1)

e) Refrigerator. A normal refrigerator with a glass door, used at a temperature of 2 C.


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SUBSTANCES

a) Distilled water (250 mL)

b) Brand green food dye. Its components are: water, propylenglycol, artificial coloring

yellow 4, red 17, blue 1 and red 14 in unknown quantities, plus propylparabene as

a conservative.

PROCEDURE

1. Get all the equipment mentioned in the list above. Use the beaker to hold the

water.

2. Measure 10 mL of distilled water in the graduated cylinder.

3. Place the graduated cylinder in the incubator until the correct temperature is

reached (for example, 2 C).

4. With the utmost care and keeping the water from getting too agitated, take the

graduated cylinder out and place it on the work table. Make sure to do the following

steps as quickly as possible to minimize temperature change.

5. Place the dye container upside down (so the dropper faces the water) and quirt

one drop of dye. Make sure it goes straight down and not down a side (if this

happens, clean the cylinder and repeat from the beginning).

6. As soon as the drop reaches the water, start the chronometer. Make sure you

watch the drop diffuse from a level surface.

7. When the drop reaches the bottom, stop the watch.

8. Register the time in seconds.

9. Repeat steps 1 through 8 fourteen more times, for a total of fifteen repetitions (at 2

C, following the example).

10. Repeat steps 1 through 9 five times, for a total of 15 repetitions per temperature (at

2 C, 23 C, 30 C, 45 C, and 58 C) or a total of 75 repetitions.


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RAW DATA

Table 1. Diffusion time (in seconds) per water temperature (in C)

Temperature

Time 1

(+/-.01 s)

Time 2

(+/-.01 s)

Time 3

(+/-.01 s)

Time 4

(+/-.01 s)

Time 5

(+/-.01 s)

Time 6

(+/-.01 s)

Time 7

(+/-.01 s)

2 C (+/-.05 C) 7.79 12.88 8.56 10.37 8.80 8.13 9.13

23 C (+/-.05

C) 11.04 8.60 8.69 8.75 7.62 11.37 13.41

30 C (+/-.05

C) 7.31 13.68 15.87 13.44 11.88 7.71 8.28

45 C (+/-.05C) 12.47 8.91 10.98 6.19 9.03 7.41 9.00

58 C (+/-.05

C) 8.75 9.25 6.63 7.03 13.31 9.00 7.75

Table 2. Diffusion time (in seconds) per water temperature (in C), continued.

Time 8

(+/-.01 s)

Time 9

(+/-.01 s)

Time 10

(+/-.01 s)

Time 11

(+/-.01 s)

Time 12

(+/-.01 s)

Time 13

(+/-.01 s)

Time 14

(+/-.01 s)

Average

time

(+/-.01 s)

8.37 12.58 7.25 7.57 8.69 10.56 10.9 9.40

9.57 10.78 8.31 11.97 10.91 11.37 9.03 10.10

8.40 7.66 14.56 7.53 15.25 14.59 6.72 10.92

7.78 13.22 7.15 9.31 15.75 8.32 7.03 9.47

9.76 8.15 8.75 5.18 6.25 7.31 9.03 8.30


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DATA PRESENTATION

Table 1.Diffusion speeds of dye in water at 2 C

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.00

11.00

12.00

13.00

14.00

15.00

16.00

17.00

18.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Timeinseconds(

+/-.01s)

Repetition number

Diffusion speeds of dye in water at 2 C

2 C (+/-.05 C)

Lineal (2 C (+/-.05 C))


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Table 2. Diffusion speeds of dye in water at 23 C

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.00

11.00

12.00

13.00

14.00

15.00

16.00

17.00

18.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Timeinseconds(+/-.01s)

Repetition number


23 C (+/-.05 C)

Lineal (23 C (+/-.05 C))


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1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.00

11.00

12.00

13.00

14.00

15.00

16.00

17.00

18.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Timeinseco

nds(+/-.01s)

Repetition number


30 C (+/-.05 C)

Lineal (30 C (+/-.05 C))


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0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.00

11.00

12.00

13.00

14.00

15.00

16.00

17.00

18.00

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Timeinsecond

s(+/-.01s)

Repetition number


45 C (+/-.05 C)

Lineal (45 C (+/-.05 C))


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Table 6. Average time per temperature category

0.001.002.003.004.005.006.007.008.009.0010.0011.0012.0013.0014.0015.0016.0017.0018.00

1

2

3

4

5

Time in seconds (+/- .01 s)

Temperatu

renumber

Average time per temperature category

Average

Lineal (Average)


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CONCLUSION

In the hypothesis, it was stated that diffusion rate would increase as temperature

increased, since temperature is directly proportional to diffusion rate1. However, this was

not the case in the experiment, since the values rise until they peak at 30 C, and then

drop back down. At a first glance, this proves the hypothesis wrong in the first place, but it

also goes against what literature says is true. There is one small detail which may redeem

this practice, though: at 2 C, the drop went down in a very controlled line, with very little

outwards diffusion, while at higher temperatures, the drop went down more slowly but it

diffused more quickly, with the drop almost disappearing practically at the start at 58 C.

This is the reason why it slowed down as temperature went up; it lost irs cohesion and

thus its contained energy, and spread around the cylinder faster, but went down slower

(since it no longer held that level of cohesion; similar to how a knife easily cuts straight

through butter and a palm will not go through the butter as quickly but it will get through

more butter). Thus, it could be said that diffusion speed does increase with temperature,

but we would need another experiment to quantify this. The data range (15x5; fifteen

repetitions per category, at five categories) is sufficient, but the data is way too dispersed

to conclude something with credibility, as shown by the very large error bars and the huge

differences between times in each repetition range. The range could have probably been

better, but that is a limitation of the equipment available to the lab.

To conclude, linear diffusion speed does not follow a set pattern (data is extremely chaotic

and the graphs are not dependable, as the very large error bars show), but it was

observed that overall diffusion rate seemed to increase as temperature increased, so the

hypothesis is correct.


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EVALUATION

This practice lacked very much in control of variables, not in amount of variables

controlled, but in the quality of a few variables; these being the waters temperature and

measurement of diffusion speed. The most egregious mistake was probably relying on the

incubators ambient thermometer rather than measuring the waters temperature directly. It

would have been far better to use a thermoagitator (ideally inside an incubator at the

desired temperature) to reach the temperature and then to quickly pour the drop, than the

method used here. Also, instead of measuring the speed at which the drop fell, it would

have been better to measure the speed at which the drop completely dissolved in the

water. The data analysis was appropriate, but perhaps it would have been better to

discriminate data in this practice, to acquire a better picture of the relationship. The

practice was very simple, so a very in-depth analysis is not needed, but some correlation

tests may have been helpful. A range with greater temperature differences would have

been more adequate, but that is a limitation of the equipment available to us (a greater

range could have been achieved using the thermoagitator). Overall, a better practice could

have resulted with more adequate equipment (namely, the thermoagitator and a

thermometer for measuring the temperature).


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ANNEXES

Annex 1. Incubator

Thermometer

Door

Grill

Temperature control

knob

On/off

switch


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Annex 2. Experiment setup

REFERENCES

1. http://www.austincc.edu/emeyerth/diffuse2.htm

2. http://www.tiem.utk.edu/~gross/bioed/webmodules/diffusion.htm3. http://www.southampton.ac.uk/~engmats/xtal/diffusion/diffusion.htm

4. http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/diffus.html

5. Miller, K. R., and J. S. Levine. Biology. Boston: Pearson Education, 2010. Print.

Dropper

Graduated cylinder
http://www.austincc.edu/emeyerth/diffuse2.htmhttp://www.austincc.edu/emeyerth/diffuse2.htmhttp://www.tiem.utk.edu/~gross/bioed/webmodules/diffusion.htmhttp://www.tiem.utk.edu/~gross/bioed/webmodules/diffusion.htmhttp://www.southampton.ac.uk/~engmats/xtal/diffusion/diffusion.htmhttp://www.southampton.ac.uk/~engmats/xtal/diffusion/diffusion.htmhttp://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/diffus.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/diffus.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/diffus.htmlhttp://www.southampton.ac.uk/~engmats/xtal/diffusion/diffusion.htmhttp://www.tiem.utk.edu/~gross/bioed/webmodules/diffusion.htmhttp://www.austincc.edu/emeyerth/diffuse2.htm


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6. Buthelezi, Thandi, Laurel Dingrando, Nicholas Hainen, Cheryl Wistrom, and Dinah

Zike. Chemistry: Matter and Change, student edition. Glencoe/McGraw-Hill.

Columbus: Glencoe/McGraw-Hill, 2008. Print.

diffusion of vegetable dye in water

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