9
DIFFUSION THROUGH A LIQUID EXPERIMENT
LABEXPERIMENT ON DIFFUSION THROUGH A LIQUID
School:
6/26/2014
Lab1: Introduction to Science
Diffusionthrough a Liquid
Purpose
Inthis laboratoryexperiment,weare tasked toapply the scientific method by conductingpreliminary analysis of thediffusion rates betweenthetwo dyes. The dyes each have different molecular weightswhich will determinethe effect of molecular weight on theircorresponding diffusionrate.
Hypothesis
Basedfrom the effect of molecular weight on the rate of diffusion for acorresponding liquid, if the dye has a higher molecular weight, thenit will have a decrease in the rate of diffusion of a liquid sample.
Data
Table 5: Diffusion through Corn Syrup (Data and Rates)
Dye Color 
Molecular Weight (g/mol) 
Initial Position 
Final position 
Total DistanceTraveled (mm) 
Diffusion Rate*(mm/hr) 
Blue 
793 g/mol 
The initial position is between (100mm107mm) 
The final position is between (85mm122mm) 
30 mm 
900 mm/hr 
Red 
496 g/mol 
The initial position is between (20mm24mm) 
The final position is between (10mm37mm) 
23 mm 
690 mm/hr 
*Multiply the total distance traveled by 30 to obtain thediffusion rate.
Table 6: Diffusion through Corn Syrup: Incremental Data
  
Diffusion (Distance, mm) 

Time (sec) 
Blue Dye 
Red Dye 
10 
2 
1.6 
20 
2.3 
2.0 
30 
2.5 
2.3 
40 
2.6 
2.3 
50 
2.6 
2.4 
60 
2.6 
2.4 
70 
2.6 
2.4 
80 
2.7 
2.4 
90 
2.7 
2.5 
100 
2.7 
2.5 
110 
2.7 
2.5 
120 
2.8 
2.5 
Table 7: Diffusion through Water: Data and Rates
Dye Color 
Molecular Weight(g/mol) 
Initial Position 
Final Position 
Total DistanceTraveled (mm) 
Diffusion Rate(mm/hr) 
Blue 
793 
The initial position is between (19mm24mm) 
The final position is between (16mm37mm) 
16 mm 
480 mm/hr 
Red 
496 
The initial position is between (100mm107mm) 
The final position is between (95mm115mm) 
13 mm 
390 mm/hr 
*Multiply the total distance traveled by 30 to obtain thediffusion rate.
Table 8: Diffusion through Water: Incremental Data
  
Diffusion (Distance, mm) 

Time (sec) 
Blue Dye 
Red Dye 
10 
0.7 
0.6 
20 
0.8 
0.7 
30 
0.9 
0.8 
40 
0.9 
0.8 
50 
0.95 
0.9 
60 
1 
1 
70 
1 
1.1 
80 
1.1 
1.1 
90 
1.1 
1.1 
100 
1.1 
1.1 
110 
1.1 
1.2 
120 
1.1 
1.2 
Observations
Based from the gathered data obtained in the laboratory experiment,two kinds of liquids were used as samples in determining the effectof molecular weight on the rate of diffusion of the dye samples: cornsyrup and water. Blue and red dyes were used in the experiment. Inusing the corn syrup as the liquid sample, we noticed that the bluedye (approx. 30 mm) has reached a longer distance traveled (ave.diameter of the dye) compared with that of the red dye (approx. 23mm). In using water, on the other hand, the blue dye (approx. 16 mm)has reached a longer total distance traveled compared with that ofthe red dye (approx. 13 mm). Moreover, for the two liquid samples, asthe experiment takes a longer time period, both dyes increase theirdiffusion, until such time that their diffusion reaches a constantvalue.
Sample Calculations
In calculating for the total distance (dye diameter) traveled by thedyes, we subtract the final positions of the dye with its initialposition.
*Consider the corn syrup as the medium sample.
**For the calculation involving the blue dye for a corn syrup medium,
Total Distance Covered = Total distance elapsed in a given timeperiod
= (122 mm – 85 mm) – (107 mm – 100 mm) = 30 mm
Based from Table 6, taking the average diffusion rate (mm/hr) for theblue dye,
R_{partial}= (d_{i}– d_{i1})/ (r_{i}– r_{i1})
For calculation, taking the partial rate of diffusion of blue dye ina corn syrup medium at time = 20 seconds,
R_{partial}=(2.3 mm – 2 mm) / (20 sec – 10 sec) = 0.03 mm/sec
Partial Diffusion through Corn Syrup
  
Partial Diffusion through Corn Syrup (mm/s) 

Time (sec) 
Blue Dye 
Red Dye 
20 
0.03 
0.04 
30 
0.02 
0.03 
40 
0.01 
0 
50 
0 
0.01 
60 
0 
0 
70 
0 
0 
80 
0.01 
0 
90 
0 
0.01 
100 
0 
0 
110 
0 
0 
120 
0.01 
0 
Average 
0.00727 
0.00818 
For the diffusion rate of blue dye in a corn syrup medium, wemultiply the total distance covered by 30:
Diff. rate = Total distance covered / elapsed time
**For the calculation involving the red dye for a corn syrup medium,
Total Distance Covered = Total distance elapsed in a given timeperiod
= (37 mm – 10 mm) – (24 mm – 20 mm) = 23 mm
Based from Table 6, taking the average diffusion rate (mm/hr) for thered dye,
R_{partial}= (d_{i}– d_{i1})/ (r_{i}– r_{i1})
For calculation, taking the partial rate of diffusion of red dye in acorn syrup medium at time = 20 seconds,
R_{partial}=(2 mm – 1.6 mm) / (20 sec – 10 sec) = 0.04 mm/sec
For the diffusion rate of red dye in a corn syrup medium, we multiplythe total distance covered by 30:
Diff. rate = Total distance covered / elapsed time
*Consider the water as the medium sample.
**For the calculation involving the blue dye for a water medium,
Total Distance Covered = Total distance elapsed in a given timeperiod
= (37 mm – 16 mm) – (24 mm – 19 mm) = 16 mm
Based from Table 8, taking the average diffusion rate (mm/hr) for theblue dye,
R_{partial}= (d_{i}– d_{i1})/ (r_{i}– r_{i1})
For calculation, taking the partial rate of diffusion of blue dye ina water medium at time = 20 seconds,
R_{partial}=(0.8 mm – 0.7 mm) / (20 sec – 10 sec) = 0.01 mm/sec
Partial Diffusion through Water
  
Partial Diffusion through Water (mm/s) 

Time (sec) 
Blue Dye 
Red Dye 
20 
0.01 
0.01 
30 
0.01 
0.01 
40 
0 
0 
50 
0.005 
0.01 
60 
0.005 
0.01 
70 
0 
0.01 
80 
0.01 
0 
90 
0 
0 
100 
0 
0 
110 
0 
0.01 
120 
0 
0 
Average 
0.00363 
0.00545 
For the diffusion rate of blue dye in a water medium, we multiply thetotal distance covered by 30:
Diff. rate = Total distance covered / elapsed time
**For the calculation involving the red dye for a water medium,
Total Distance Covered = Total distance elapsed in a given timeperiod
= (115 mm – 95 mm) – (107 mm – 100 mm) = 13 mm
Based from Table 8, taking the average diffusion rate (mm/hr) for thered dye,
R_{partial}= (d_{i}– d_{i1})/ (r_{i}– r_{i1})
For calculation, taking the partial rate of diffusion of red dye in awater medium at time = 20 seconds,
R_{partial}=(0.7 mm – 0.6 mm) / (20 sec – 10 sec) = 0.01 mm/sec
For the diffusion rate of red dye in a water medium, we multiply thetotal distance covered by 30:
Diff. rate = Total distance covered / elapsed time
Conclusion
Based from the experiment conducted by Alexander Ken Libranza (2012),results showed that at a higher molecular weight of the liquid, therewould be a corresponding decrease in its diffusion rate, assuming aconstant given temperature. In the experiment, using both corn syrupand water as the liquid medium sample, the blue dye which hasactually a higher molecular weight, constitutes a higher rate ofdiffusion than the red dye. Errors were made in the results of theexperiment since several assumptions were done to provide an inverserelationship between the molecular weight and the rate of diffusion.According to Ernest Capraro (2010), there are several factors to beconsidered which can provide a direct impact on the rate of diffusionof liquids: speed, mass, and resistance to movement. Thus, we cannotactually say that the molecular weight of the liquid sample is thesole factor in determining the diffusion rate of a liquid sample.
Questions

If the dye has a higher molecular weight, then it will have a decrease in the rate of diffusion of a liquid sample.

In the experiment, using water and corn syrup as the liquid medium to be used, the hypothesis of having an inverse relationship between the molecular weight and diffusion rate were not proven significant. The red dye, which has a molecular weight of 369 g/mol, has a lower diffusion rate in comparison with the blue dye which has a molecular weight of 793 g/mol, using both corn syrup and water as the medium sample.

Based from the graphs obtained based from the data figures in Tables 6 and 8, the independent variable is the time allowed in the experiment, whereas the dependent variable is the diffusion obtained by the blue and red dyes. (see attached .xls file for the obtained graphs)

In using corn syrup as the liquid sample, the fastest diffusion rate was obtained by the blue dye, with a diffusion rate of 900 mm/hr. On the other hand, the blue dye still has obtained a higher diffusion rate of 480 mm/hr.

Theoretical explanations said that there is an inverse relationship that exists between the molecular weight of the dye and its rate of diffusion. Hence, from the results of the experiment, theoretical explanations were not proven significant since at higher molecular weight, a faster rate of diffusion was also obtained based from the experiment.

Based from the obtained results in the experiment, the rate of diffusion through a liquid sample changes over time. Hence, since there are several factors to be considered which could affect the rate of diffusion of a liquid sample, there will be a tendency of acquiring an erroneous value for the calculated diffusion than its actual rate of diffusion.

According to Capraro (2010), "In thicker, more viscous fluid, diffusion occurs at much lower rate than in light, thin fluids with lower viscosity." Corn syrup is naturally a more viscous fluid than water. Hence, the medium for which the dye diffuses naturally affects its rate of diffusion, thereby committing errors on the obtained results in the experiment since opposite results were obtained. In relation to the transport of nutrients into the cell, the desired medium for which the nutrient diffuses shall contain smaller particles at a lesser viscous medium in order to provide a smooth and faster transfer to other parts of the human system.
References
Capraro,Ernest. (2010). Diffusion Rates. Sciences:360.Retrieved 25, June 2014 from<http://www.sciences360.com/index.php/diffusionrates8788/>
Libranza,Alexander Ken. (2012). The Effect of Molecular Weight on the Rate ofDiffusion of Substances. Retrieved 25, June 2014 from<https://www.academia.edu/1776814/The_Effect_of_Molecular_Weight_on_the_Rate_of_Diffusion_of_Substances>