IB Chemistry SL

Data and Observations

To fulfill the purpose we did the following experiments below:

Measuring pH of saltwater using several indicators in all three intertidals
Temperature (°C) in all three intertidals
Hardness of Water - presence of Ca⁺² and Mg⁺² in all three intertidals
Density of Saltwater
Distillation of Saltwater

Density of Saltwater

D= m / v |D= Density | M= Mass | V = Volume |
Mass of distilling flask = 201.60 g
Mass of distilling flask + 200 ml of H₂O = 403.00 g
Mass of saltwater = 201.40 g
Volume of saltwater = 200 ml
D = 201.40 g / 200 ml = 1.007 g / ml
Density of Saltwater = 1.007 grams per milliliter

Distillation of Water

Reference Table

Salt Water - Water found in oceans and seas. Contains at least 3%(30 parts of salt to 1000 parts of water) salt.

Hard Water - Water that contains minerals especially Calcium and Magnesium. Causes soap to precipitate, producing a scum, curd or scale in boilers.

Polluted Water - Water that contains a combination of impurities consequently being unusable for a desired use.

Purified Water - Water that had pollutants removed or rendered harmless.

Mass of Distilling Flask + Salt = 211.88 g
Mass of Salt = 10.28 g
Mass of Saltwater = 201.40 g
To find percentage of salt in saltwater we divided the mass of salt by the mass of the saltwater.
% of Salt = 10.28 g / 210.40g = 5 % of the Saltwater is Salt

IB Chemistry SL Conclusions

The water loses its basic characteristics from the high intertidal to the low intertidal. When testing the hardness of water, we found out that Calcium and Magnesium were more abundant in the more basic area, the high intertidal. The low intertidal area was softer, therefore it contained less Ca(OH)₂ and Mg(OH)₂ and was more acidic.
The pH of ocean water is relatively constant, generally falling within the range of 7.8 - 8.3 with an average value of 8.1. This constancy of pH is a attributed principally to the buffer system of dissolved carbon dioxide, carbonate and bicarbonate ions. Some pH variations are due to temperature shifts and biological activity. Diurnal changes as large as 1.5 pH units have been reported for shallow waters and heavy rainfall may cause a considerable change in pH. When testing the water for its pH we found out that the results were different. Therefore, it may be concluded that in shallow waters the pH is higher.
When testing the same water samples at the sampling site, the results of the tests were different. This was due to the time lapse between the tests done when the water was collected and the two days after, in school. The results completed at the sampling site are more reliable because of the shorter time between the sampling and analysis.
There were slight temperature differences among the three zones studied. Cool water can hold more oxygen than warm water, because gases are more easily dissolved in cool water. Therefore the shallow water contains less oxygen.

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