How Big Can a Cell Get? Practical

Today we did an experiment on the rate of diffusion of cells and the pH of some common liquids.
We used red cabbage juice agar because it changes to a variety of colours when mixed with different bases and acids. My group's liquids were white vinegar, baking powder solution and 100 plus.

PART 1

The agar block was cut into 3 pieces of each size: 5 x 5 x 5mm, 5 x 5 x 20mm and 10 x 10 x 10mm.
They were then placed into 3 petri dishes containing the 3 different liquids. We took down the amount of time taken for the agar blocks to change colour completely (to the core).

Table 1

Paper towel/ Agar block	5 x 5 x 5mm	5 x 5 x 20mm	10 x 10 x 10mm
Surface area (S)	150mm^2	450mm^2	600mm^2
Volume (V)	125mm^3	500mm^3	1000mm^3
S:V ratio	6:5	9:10	3:5
Time for agar block to change colour (vinegar)	3:38 min	4:15 min	7:59 min
Time for agar block to change colour (baking powder)	11:23 min	16:30 min	27:00 min
Time for agar block to change colour (100+)	2:35 min	3:23 min	5:38 min

PART 2

We also soaked 30 x 20mm paper towel strips in the cabbage juice, left them to dry, and then introduced a few drops of each liquid onto each paper strip. Finally we poured an equal amount of each liquid into 3 test tubes and added equal volumes of cabbage juice to each of them The colour changes of the agar blocks in part 1, the paper strips and the cabbage juice were recorded.

Table 2

Materials	Colour Change	Vinegar	Baking Powder	100+
Agar	Initial Colour	Dark purple
	Final Colour	Red	Green	Light purple
Paper towel	Initial Colour	Light purple-blue
	Final Colour	Darker purple	Green	Light purple
Cabbage juice	Initial Colour	Dark purple
	Final Colour	Red	Green	Pink-purple