Cube argumentation by Adil and Harold

Claim

Our claim was that Explanation one which is: Cells that have a larger surface area to volume ratio are more efficient at diffusing essential nutrients, is correct,

Evidence  

5 minute trial (figure 1)

side length	penetration depth	surface area to volume ratio	%of cube penetrated
.5cm	0.4cm	12	100%
1cm	0.4cm	6	98.30%
2cm	0.4cm	3	78.40%

2.5 minute trial (figure 2)

side length	penetration depth	surface area to volume ratio	%of cube penetrated
.5cm	.2cm	12	99.20%
1cm	.2cm	6	78.4%
2cm	.2cm	3	48.80%

rate of diffusion .08cm per minute `

Reasoning

From our evidence we concluded that explanation 1 was correct. This is because we found that the cube with the highest surface area to volume ratio was the most efficient at diffusing the vinegar throughout itself.  This may seem questionable considering the results in the last column of figure 1 but it is not. When the vinegar penetrates the cube it does so from all sides of the cube. If one wanted to calculate the volume of the cube the vinegar penetrated they would  get a side length. Since the cubes got penetrated .4 cm one might think that is the side length however since the cube is penetrated on all sides that length needs to be doubled. It then becomes apparent that, the volume the vinegar penetrated is more than the volume of the smallest cube. This means this cube was clear while the rest of the cubes had more time in the vinegar. So to make things more clear we halved the time and put new cubes of the same sizes in vinegar. This resulted in half the penetration of the 5 minute trial this and the fact that the different sized cubes got the same amount of penetration in the same amount of time supports the idea that the rate of diffusion is constant. So since the rate of diffusion is constant then the only thing that could affect the efficiency of the cell is the surface area to volume ratio. We found in every case the cell with the highest surface area to volume ratio was the most efficient. In both trials the cell wit the surface area of 12 (the highest) had nearly 100% penetration. The smallest cell has more places for the vinegar to enter relative to how much space the vinegar has to fill this is why it is more efficient.

Alternative claim

In our Cell size and diffusion experiment, through data analysis and calculations, we said that claim 1, i.e. Cells that have a larger surface area to volume ratio are more efficient at diffusing essential nutrients was correct . However, our alternative claim is also stated below.

Alternative Claim: The rate of diffusion is related to cell size. Nutrients diffuse at a faster rate through small cells than they do through larger cells.

refutation

The rate of diffusion does not rely on the size of the cell. From our experiment, we came to a conclusion that no matter what the size is, vinegar would diffuse into the agar cube with the same rate on all 6 sides.  We found this rate to be .08 cm per minute. However, we tend to see that smaller cubes become clear much faster than others, this is a true statement because these cubes tend to have a higher surface area to volume ratio,  but the rate of diffusion was constant . We did two trials and from both of them, we calculated the rate of diffusion for all 3 cubes and the value was approximately the same. The next time trial we did the same thing but for only 2.5 minutes. The rate of diffusion was still the same. Therefore, we can make a conclusion that the efficiency of the cell depends more on the surface area to volume ratio than to the size of the cell because if it relied on the size of the cell, than we would have got different rates for each cube depending on their size, but instead we got same type of rates. That is why the Alternative claim is not the right choice.