There are two types of hardness; temporary hardness and permanent hardness. Temporary hardness is caused by Calcium Hydrogencarbonate and Magnesium Hydrogencarbonate, while Permanent hardness is caused by Calcium Sulphate and Magnesium Sulphate.
Some hardness can be removed:
- Temporary hardness is removed by boiling.
Ca(HCO3)2 (aq) CaCo3 (s) +H2O (l) + Co2 (g)
- Both hardness are removed by adding Sodium Carbonate.
Ca 2+ (aq) + Co3 2- (aq) CaCo3 (s)
- Both hardness are removed by ‘ion exchange columns’. These are compounds with lots of sodium ions and ‘exchange’ them for Calcium or Magnesium ions.
Prediction:
Upon the light of the scientific knowledge I predict the following as elaborated by the graphs.
Lather:
As approved by the scientific knowledge I assume that the softer water will produce more lather and the harder water will produce less lather.
Scum:
I predict that the harder water will produce more scum whereas the softer water will produce no or very little scum.
I predict that the softer water will be more neutral and therefore closer to PH 7, it is also true vice-versa.
All the tests involving Silver Nitrate, Hydrochloric Acid, and Barium Chloride will identify the hardest as the one with the most precipitate.
Variables:
To produce a fair and efficient experiment I shall keep some variables constantly the same throughout the experiment and to all the test tubes containing the different types of water. The variables that have to be decided by me as which will be constant and which will vary from test tube to test tube are:
- Hardness of solution
- Surface area
- Solution volume
- Number of shakes
- Temperature
- Mass of Soap
I will have different hardness’s of solution because the purpose of the experiment is to test the reaction of various hardness’s to the chemicals used to test them.
I will keep the surface area of the solution the same as to minimise the probability that one test tube will have more space for soap to react with the solution, thus preventing the destruction of the purpose of the experiment. For the same reason I shall keep the solution volume the same.
I will keep the number of shakes given to the test tube the same for all the test tubes so as to prevent one solution having more space to react with the soap.
I will keep the temperature constant because soap could dissolve faster in certain temperatures, due to the fact that liquids dissolve better than solids thus unbalancing my experiment.
I will keep the mass of soap used constant to prevent one solution from having more soap to react with and produce more lather, thus destroying the purpose of the experiment.
Below is the finished table of the variables and non-variables:
Plan of Investigation:
I will use the five different types of solutions A, B, C, D and E. I will use a constant surface area by using the same type of test tube for all the solutions.
I will use 5 cmg 3 gof solution as the volume, and I will shake all test tubes five times. I will use room temperature to conduct my experiment in, and I will use 10 g of soap in each solution.
Apparatus:
Method:
-
I filled a measuring cylinder with 5 cm 3 gof solution A then transferred it to a test tube.
- I repeated step one with the rest of the solutions.
- I measured 10 g of solid soap 5 times and transferred them to the test tubes.
- I put on the stopper and shook the solution 5 times.
- I measured the amount of lather and scum, and noted all the differences.
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I repeated steps 1 – 5 but using 5 mm 3 gof liquid soap.
-
I repeated steps 1 – 5 but using 5 mm 3 gof detergent.
- I Repeated steps 1 and 2 then I put in litmus paper and compared it with a diagram to find the exact PH of the solutions.
- I repeated steps 1 and 2 then I added Sliver Nitrate and noted the amount of residue.
- I repeated step 8 with Hydrochloric Acid
- I repeated step 8 with Barium Chloride
Observation:
During the experiment I observed that the harder solutions made a lot of scum with the soap while the softer solutions created a lot of lather.
Upon inspecting the solutions during and after the experiment I came up with the following observations:
In Liquid Soap:
In Solid Soap:
In Detergent:
Tests:
PH:
Chloride:
Carbonate:
Sulphate:
Residue:
Conclusion:
I therefore conclude upon the light of the observations from my experiment that my predictions and hypothesis were correct and that the softer solution produces more lather while the harder solution produces more scum, and that the softer solutions are closer to PH 7.
Evaluation:
Upon finishing and observing my experiment I saw flaws that could be patched in future experiments to improve the results and outcomes:
- I could do more than two experiments for each test and take an average of the results to increase the accuracy of the results obtained.
- I could do experiments with a wider range of solutions so that I get a clearer view of the hardness of natural solutions.
