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THE EFFECT OF SURFACE AREA VOLUME RATIO ON DISSOLVING OF AGAR IN
HYDROCHLORIC ACID
RESEARCH QUESTION: What is the effect of surface area volume ratio on dissolving of agar in
hydrochloric acid?
INTRODUCTION: Diffusion is known as the passive movement of the particles from its higher
concentration to its lower concentration without energy. This is the reason why some big molecules
cannot diffuse but small ones could diffuse such as monomers, ions, etc.
Temperature, size of the molecules, concentration gradient, and surface area to volume ratio are some
factors that affect the diffusion rate. With this experiment the effect of surface area to volume ratio on
the diffusion rate will be examined.
AIM: To see the relation between surface area and volume ratio.
HYPOTHESIS: I expect that the one which have the bigger value of surface area volume ratio will
dissolve firstly.
VARIABLES
INDEPENDENT VARIABLES: It is the surface area volume ratio of the agar blocks.
DEPENDENT VARIABLES: It is the time taken for the disappearance of the red colour in the block.
CONTROLLED VARIABLES: Since the effect of one factor is examined the other factors should
be kept constant. Temperature and the concentration of the acid were kept constant. The experiment
took place in room temperature and for different sized agar blocks the same concentration of acid is
used.
APPARATUS:
 One large block of agar
 Knife
 Chopping board
 100 cm3 hydrochloric acid
 5 beakers (100 ml)
 Stopwatch
METHOD:

Cut the large agar block into different cubes that have different dimensions.

Add 60 cm3 hydrochloric acid to the each beaker.
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
Put the agar cubes, which have different sizes, into the beakers at the same time and start the
time immediately.

The time taken for the disappearance of the red colour in the agar cube recorded for each of
the agar cube.
DATA COLLECTION
Agar Cubes
Cube 1
Cube 2
Cube 3
Cube 4
Cube 5
Dimensions/cm
0.9x1.5x1.7
0.9x2.2x1.4
0.9x2.0x2.3
0.9x3.1x2.2
0.9x2.4x2.2
Tablo 1: Dimensions of the Agar Cubes
Agar Cubes
Surface Area/cm2
Volume/cm3
Surface
area/Volume
Time taken/s
(±0.1)
Cube 1
Cube 2
Cube 3
10.86
12.64
16.94
2.295
2.772
4.140
4.732
4.560
4.091
310
323
342
Cube 4
Cube 5
23.18
18.57
6.138
4.752
3.776
3.907
380
375
Tablo 2: Surface Area Volume Ratio of the Agar Cubes
Time taken/s
450
400
350
300
250
Time taken/s
200
150
100
50
0
0
1,000
2,000
3,000
4,000
Graph 1: It Shows The Relation Between Surfaca Area Volume Ratio And The Diffusion Rate
5,000
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CONCLUSION AND EVALUATION
The experiment shows that if the surface area volume ratio gets bigger the diffusion rate increases. It
means that when the surface area volume ratio decreases the amount of HCl enters the agar block
decreases. So the bigger surface area volume ratio causes increasing diffusion rate.
I do not have much time while doing the experiment so I could not repeat the experiment to get
accurate values for time and I took the cubes whose surface area volume ratios are very close to each
other so the red colour disappears immediately so while I record the time I could catch the real time
that the block disappear.
It is very difficult the record the time and observe the agar cubes into the acids. I tried to do it but I
think I could not ménage it so well so it caused some mistakes and errors.