02_A_Agar+experiment


 * Agar-Agar!**

**Aim** The aim of this experiment is to explore the relationship between surface area to volume ratio and rate of exchanging materials.

The smaller the cube, the higher the rate of conductivity since the volume of the cube would be smaller.
 * Hypothesis**


 * Apparatus/ Materials**
 * Razor blade/ Scapel
 * White tile
 * Ruler
 * Stirrer
 * Stop Watch
 * 3 Beakers
 * 3 pieces of 2 x 2 x 2 solid agar
 * Data logger with conductivity probe
 * Methodology **
 * 1) Cut one of the agar pieces into 8 cubes such that each side is 1cm in length.
 * 2) Cut another agar piece into 64 cubes with a length of 0.5cm each.
 * 3) Leave the last agar piece as it is.
 * 4) Fill a beaker with 200ml of tap water and place the conductivity probe in the water.
 * 5) Put the 2 x 2 x 2 agar block, which is also the largest block into the beaker.
 * 6) Click the run icon in the data logger.
 * 7) Stir the water continuously and gently while the data logger takes the reading every 10 seconds.
 * 8) Use the stopwatch to time for 2 minutes.
 * 9) Stop the data logger after 2 minutes and record the data.
 * 10) Repeat steps 6-9 for the 8 cubes of 1 x 1 x 1cm and 64 cubes of 0.5 x 0.5 x 0.5c

**Results** 2 x 2 x 2 Agar block
 * No of Pieces of Agar cubes || Length (cm) || Surface Area (cm2) || Volume (cm3) || Surface area to volume ratio || Rate of conductivity change ||
 * 1 || 2 || 24 || 8 || 3:1 || 1.2 ||
 * 8 || 1 || 6 || 1 || 6:1 || 0.53 ||
 * 32 || 0.5 || 0.15 || 0.125 || 6:5 || 1.94 ||

1 x 1 x 1 Agar blocks

0.5 x 0.5 x 0.5 Agar blocks

**Results Analysis** __2 x 2 x 2cm agar cube__ 1. The ratio of surface area to volume is 3:1. 2. The rate of conductivity change is 1.2

__1 x 1 x 1cm agar cubes__ 1. The ratio of surface area to volume is 6:1. 2. The rate of conductivity change is 0.53

__0.5 x 0.5 x 0.5 agar cubes__ 1. The ratio of surface area to volume is 6:5. 2. The rate of conductivity change is 1.94

__What precautions did you take in this experiment?__ We did not hit the conductivity probe against the glass beaker we felt that it might affect the results.
 * Discussion **

__What can you infer from the results above?__ I can infer that the higher the ratio of surface area is to volume ratio, the higher the rate of conductivity.

__Compare this experiment with the one that you did in Lower Secondary where coloured agars were soaked in acid. Which do you think is more accurate?__ I think that this experiment is more accurate since we have a machine to help us get the values.

__How do you relate this to the shape of simple (e.g. earthworm) to complex (e.g. tiger) living organisms?__ Complex living things require efficient diffusion of nutrients to their bloodstream unlike simple organisms. Therefore complex living organisms have a greater surface area, which are the organs in the organism.

__Once a cell grows to a certain size it becomes too large for the complete diffusion of needed substances throughout its cytoplasm. As a cell grows, is the surface area of the cell membrane as efficient relative to the volume of the cell?__ When the cell grows, the surface area of the cell membrane is not as efficient relative to the volume of the cell since the ratio does not increase proportionately (the volume increases faster than the surface area).


 * Errors made**
 * 1) We did not stir the agar pieces with equal strength throughout. This may affect the experiment results.
 * 2) We might not have cut the agar blocks accurately.