Potato Cube

IS BIGGER BETTER?

By: Hendrich/ 11Dp2

Aim: To investigate the relationship between surface area and volume in the uptake of water in potato cubes.

Research question: п‚ÑŸ Is bigger better?

п‚ÑŸ What is the relationship between surface area and volume in the uptake of water in potato cubes?

Basic Theory: Fermentation is an important process in the production of a number of substances used by humans. It involves the enzyme conversion (in the absence of oxygen) of sugar into alcohol and carbon dioxide Beer-making and wine-making are two examples of process that make use of yeast as the microbial fermenting agent. Research continues to be undertaken to improve the efficiency of the processes. Until recently, the yeast suspension was mixed with �sugar’ solution and when fermentation was complete, the yeast had to be separated by a complex filtration process. Biotechnologist discovered they could �trap’ yeast cells in jelly balls made of sodium alginate. This slows down the fermentation process but eliminates the need for complex filtration because the yeast cells are immobilized in the jelly and are not able to disperse in the fermenting solution. This has the potential to increase cost-efficiency. In further experiment, the experimenters set out to find the optimum jelly ball size. To do this, they started with equal amounts of yeast and equals amount of sodium alginate, and varied the size of the jelly balls they made. Which jelly size is more efficient in the fermentation process? It has been found that the answer to this question depends not on the surface area of the balls, but on the ration of surface area to the volume enclosed. In organism the surface area over which diffusion takes place must he sufficient to complete the needs of the respiring tissues. It is a simple mathematical rule that as an object increases in volume, the ratio of its total surface area to its volume decrease. In other words, the larger the object, the smaller is its surface-volume ration

Hypothesis: The 8 пÑ"Ñš 1x1 cm of potatoes will absorb more water than the 2x2cm potato, because the smaller potato can have more rooms (8 вЂ?rooms’) to contain more waters.

Variable: Independent в†' The starting size of both potatoes (1пÑ"Ñš 2x2 cm and 8пÑ"Ñš 1x1 cm)

Dependent в†' The mass of both potatoes every 15 minutes (for 75 minutes)

Control в†' п‚ÑŸ Time (I measure the potatoes every 15 minutes)

п‚ÑŸ The surface (volume ratio) of the potato, 1x1cm (8 cubes) and 2x2cm (1 cube)

Material:

• Potato

• Ruler

• Knife

• Running water

• Tissue papers

• Electronic Scale

• 2 пÑ"Ñš Beaker Glass

• 2 пÑ"Ñš Spatula

• Distilled water

• Stopwatch

Procedure:

1. As accurately as possible, cut a potato cube with 2 cm sides, make sure there is no skin on it

2. Cut another cube with 2cm sides, but this time subdivide it further as shown in figure 1

3. a. Wet the 2 cm cubes under running water and dry it with a paper tissue, then weigh it on the electronic balance. Record the mass in table 1, column A. Put this cube in a 100 ml beaker labeled �column A’.

b. Wet The eight 1 cm cubes under running water and dry them with a paper tissue, then weigh them together and record their combined mass in table 1, column D. Put these cubes together in another 100 ML beaker glass labeled �column D’.

Time

(min) A

Mass

(g) B

Cumulative mass change

(g) C

%

Increase mass D

Mass

(g) E

Cumulative

Mass

Change

(g) F

%

Increase in mass

0

15

30

45

60

75

4. Cover the cubes in both beakers with distilled water. Make this time = 0 in table 1. During the next 15 min, occasionally turn the cubes with the glass stirring rod or spatula

5. After 15 min, drain the water from both beakers and put the cubes on several thicknesses of paper towel. Let them dry with a paper tissue (try to be consistent in the way you dry them).

a. Weigh the 2 cm cube as before and record its mass in table 1, column A, time = 15 min

b. Weigh the eight 1 cm cubes as before and record their total mass in table 1, column D, time = 15 min. Place the cubes back in their respective beaker and cover with distilled water again.

6. While waiting to take the next measurements, start your calculations, see the calculations box below.

7. After another 15 min, repeat step 6. Repeat again at the times indicated in table 1. If time is running out, omit the 75 min reading

8. Dispose the cubes in the bin labeled �organic’

9. Complete the calculations for table 1

Table 2

Beaker A Beaker