Agar+Experiment+Report

__**Aims**__ This experiment is to explore the relationship between surface area to volume ratio and rate of exchanging materials. In this experiment, there are three 2cm x 2cm x 2cm3 of solid agars. The agars would be cut into different sizes of surface areas of 4cm2, 1cm2 and 0.25cm2 and the different volumes would be. The different cube sizes would be placed in tap water and using a data logger, we would be able to determine the different rates of diffusion of the different cubes (if the surface area and volume affects it). The cells used are agar cells where the substances would move from a higher concentration to a lower concentration.

__**Prediction**__ According to Fick’s law, the rate at which a substance can diffuse is affected by the surface area as:

**Rate of Diffusion = surface area x concentration difference / distance** As diffusion would be affected by the surface areas, and when the surface area is bigger, more substances would be able to diffuse at the same time. However, i feel that the agar with the smallest surface area, 0.25cm2 would diffuse the fastest and easiest. The explaination behind my prediction is because: As organisms get bigger their volume and surface area both get bigger, but volume increases much more than surface area. This can be seen with some simple calculations for different-sized organisms. In these calculations each organism is assumed to be cube-shaped to make the calculations easier. The surface area of a cube with length of side L is L x L x 6 (6L2), while the volume is L3. This means that as organisms become bigger it becomes more difficult for them to exchange materials with their surroundings.

__**Results**__ **Rate of Conductivity Change for 1 piece of Agar** || **Time (s)** || **Conductivity I/O-1(mS)** || 0 || 0.23 || 10 ||  0.41 || 20 ||  0.55 || 30 ||  0.72 || 40 ||  0.96 || 50 ||  1.04 || 60 ||  1.15 || 70 ||  1.22 || 80 ||  1.26 || 90 ||  1.3 || 100 ||  1.4 || 110 ||  1.47 || 120 ||  1.54 ||

**Rate of Conductivity Change for 8 pieces of Agar** || **Time (s)** || **Conductivity I/O-1(mS)** || 0 || 0.1 || 10 ||  0.38 || 20 ||  1.07 || 30 ||  1.45 || 40 ||  1.48 || 50 ||  1.7 || 60 ||  1.85 || 70 ||  1.99 || 80 ||  2.15 || 90 ||  2.31 || 100 ||  2.38 || 110 ||  2.51 || 120 ||  2.66 ||

**Rate of Conductivity Change for 64 pieces of Agar** || **Time (s)** || **Conductivity I/O-1(mS)** || 0 || 0.86 || 10 ||  2.66 || 20 ||  3.07 || 30 ||  3.21 || 40 ||  3.51 || 50 ||  3.79 || 60 ||  4.1 || 70 ||  4.36 || 80 ||  4.68 || 90 ||  4.83 || 100 ||  4.93 || 110 ||  5.13 || 120 ||  5.26 || **No. of pieces of agar cubes** || **Length (cm)** || **Surface Area (cm2)** || **Volume (cm3)** || **Surface Area to volume Ratio** || **Rate of Conductivity change** || 1 || 2 ||  4 ||  8 ||  1:2 ||  1.31 || 8 ||  1 ||  1 ||  8 ||  1:8 ||  2.56 || 64 ||  0.5 ||  0.25 ||  8 ||  1:32 ||  4.40 || __Discussion__ From the data collated, we can tell that the gradient of conductivity of the different sized cubes are relatively constant and gentle. However, the numerical data of the conductivity are different, with the 0.25cm2 agar cubes having the largest rate of conductivity. In fact, the rate of conductivity change increases as the number of agar cubes increases and the surface area of each cube decreases. __Discussion Questions:__ //What precautions did you take in this experiment?// I had to make sure that the cubes that were cut were of the same size and volume, least the same type of agar (supposedly same size, volume and surface area) had different dimensions and this would affect the results as the constant is not kept. Most importantly, the constants had to be kept, for example, the amount of liquid used, the time placed in water and et cetera. The constant has to be kept to prevent the results from becoming different and inaccurate.

//What can you infer from the results above?// I can infer that the 64 pieces of agar cubes had the highest conductivity change, as their rate of conductivity change is 4.4, which is the highest compared to the other 2 results. This shows that the smaller the object, the faster and easier the rate of diffusion and the higher the rate of conductivity, as of contrary to the common misconception that the bigger the agar is, the faster it diffuses.

__Conclusion__ The more the number of agar cubes and less surface area of each cube, the more the conductivity rate, where it is faster and easier to diffuse.