Variables


Ø  Variables
                               
-       Dependent variable: These are the ones which depend of the independent variable, that is, the changes produced by the independent variable represent the dependent variable. They are the following ones:

o   The changes and effects on the development of the life of bacteria produced by different substances used. It also affects to the time these bacteria will be alive. 

o   The solubility of the substances will be higher or lower depending on the quantity used. 

o   Depending on the type of bacteria used, the substances will produce different effects. 


These variables are measured:

ü  For measuring the solubility we use the next formula: S = (mass of the solute / mass of the solvent) x 100. By doing this calculations we found how much solubility this solution will have. We divide the quantity of the solute (in this case bacteria found in a cigarette) into the quantity of the solvent (water). Then we multiply the result by 100. 

ü  We measure the changes and effects on the development of the life of bacteria by observation.

-       Independent variable: These are the ones that we determine, which are the following ones:

o   The substances chosen (ammonia, hexamine, carbon monoxide, toluene and aniline) as a solute. 

o   The solvent (water) chosen to dissolve the solute and create a solution. 

o   The quantity of these substances used.  

These variables are measured with weighing scales, pipettes... 



-       Controlled variable: Pressure, ambient temperature (20ºC-25ºC), humidity...

-       Qualitative variable: They refer to characteristics or qualities that can not be measured with numbers.

Solutions
Color
Smell
Segmentation
Flask 1 (0,0033g/ml)
Yellowish
It doesn’t smell.
It doesn’t have any segment because is a total liquid solution.

Flask 2 (0,0067g/ml)
Very light brown
It doesn’t smell.
Flask 3 (0,0100g/ml)
Light brown
It smells a bit tobacco.
Flask 4 (0,0144g/ml)
Brown
It smells tobacco.
Flask 5 (0,0256g/ml)
Dark brown
It smells tobacco.
Flask 6 (0,0333g/ml)
Totally dark brown
It smells strongly of tobacco.
First flask (not totally diluted) solution)
It is totally dark brown, but at the top there is a big amount of tobacco’s pieces, which are more like light brown with different contrasts.
The two solutions look equal because they contain the same measures and type of tobacco.
They both have a strongly and disagreeable tobacco smell, specially due for the amount of tobacco’s pieces concentrated at the top of the solution.
There are a lot of small pieces of tobacco around the solution, which is clearly not totally dissolved. These pieces are small because we mashed up them before, that is, they probably will be bigger than now.
Second flask (not totally diluted solution)

The numbers show the quantity of tobacco or water in each solution (the right one is water and the left one is tobacco).



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