In this experiment I am investigating the relationship between surface area and the volume of a model cactus and to determine whether this relationship affects the loss of water. We used oasis blocks, an absorbant material used by florists as a substitute for a cactus, that would soak up the water, and thus ideally show the percentage water loss by weighing the before and after evaporation weights.
The independent variable is the total surface area for each size of the blocks and I think this will affect the dependent variable as larger blocks, I hypothesize, will have less water loss by evaporation as there is less surface area for it, as opposed to the smaller (2cm x 2cm x 2cm) blocks, that have a larger total surface area for water to evaporate. Dependent Variable
The dependent variable is the percentage loss of water, and I think this will be affected by the independent variable, the total surface area of the blocks, because I hypothesize that the larger the total surface area, the more water loss will occur, as the oasis will have more places for the evaporation to take place. Control Variables
The control variables are the size and shape of the oasis blocks within each category, the size of the tray, and the conditions that the blocks are left in to saturate and evaporate, and these are important to keep controlled as the shape and size can alter the surface area, which will in turn distort the results. this is the same of the size of the tray, which could potentially alter water distribution, and the conditions that the trays are left in could drastically change the rate of evaporation.
I will change the independent variable in the way that I will test three different sizes of blocks: - 1 x (8cm x 8cm x 4cm)
- 4 x (4cm x 4cm x 4cm)
32 x (2cm x 2cm x 2cm)
I will use a metal ruler with as much accuracy as possible to ensure that the test is fair. I will control the controlled variables by:
Ensuring that the shape and size is constant within the different variant groups of the independent variable, by measuring all sides with a ruler. Re-using the same tray (after cleaning it each time).
Leaving the tray for two days in the same place each time to control the environment to the fullest of my ability.
Controlling of Variables
Unfortunately, in the time frame we had to complete and document this experiment there was not enough time to repeat the experiment in order to carry out an error analysis by use of standard deviation. The apparatus I will use to control the pre-mentioned variables are as follows: Metal ruler
Electronic balance set to 0.00g
Large blocks of oasis material
The method I used in order to generate the most useful results possible is as follows: Cut the oasis block with the metal ruler into pieces with measurements of 8cm x 8cm x 4cm. Cut the remaining oasis block into 4 cubes with measurements of 4cm x 4cm x 4cm. Cut the remaining oasis block into 32 cubes with measurements of 2cm x 2cm x 2cm. Record the mass (in g, ±0.01g) of the three groups of different sized oasis blocks. Place the sets in a large tray and saturate them by filling the tray with water. Leave them for 1-3 days until they are fully saturated and record their saturated masses within the sets, taking mistakes or uncertainties into consideration.. Empty the tray of water and replace the blocks, leaving the trays near a window to allow evaporation over 1-3 days. Record the evaporated mass of each set, keeping uncertainties in mind.
Size of oasis blocks (cm)
±1mmVolume (cm3)Surface Area (cm2)SA:V Ratio
8 x 8 x 42562561:1
4 x (4 x 4 x 4)2563841.5:1
32 x (2 x 2 x 2)2567683:1
Size of oasis blocks (cm)
8 x 8 x 44.49226.58222.65
4 x (4 x 4 x 4)4.90241.31238.03
32 x (2 x 2 x 2)4.78225.91210.93