[wig]

We did a lab comparing the density of ocean water from 2 different locations. Are my answers to these questions correct?

5)The average density of ocean water is 1.03 g/mL.  If you were to compare our result with the average density of water, why is it better to compare our three class  average density rather than use your result?

It is better to compare the average density of the three classes because in order for it to be a fair comparison, they need to be standardized. If we pick a random result from our data set, it will not be accurate because each result has a different deviation from our average.

6) Can you think of a reason why our result for the density was lower than the accepted value for the average density of ocean water?

A possibility for our result for the density being lower than the accepted value for the average density of ocean water is that since ice has a lower density than water, the water at Bewicky park might have been at a colder temperature.

For question 6, I was wondering since each glassware that we used to measure volume are not 100% accurate (e.g. the volumetric pipette has a standard error of 0.02 mL), is that the reason why our density is lower than the accepted value?

[Borek]

You should take the measurements always at the same temperature to make the results comparable, so no, temperature at which the sample was collected should not matter.

Think about geography of the place you took your sample from (I guess you mean Bewicke park in Vancouver?). Was it raining previously? How easily does the water in the Harbor mix with the open ocean water? Are there any rivers discharging into the Harbor?

You have mentioned ice - was there ice present? Was it just frozen water from the harbor, or frozen water covered with the precipitation? Does the rain/snow contain any salt? What is the density of water from precipitation?

[Enthalpy]

Dissolved salts are already mentioned. The amount varies a lot with the location, the depth, the currents... Rivers and glaciers use to bring fresh water but evaporation concentrates the salts, for instance in the Mediterranean. Dissolved gases tend to be less important.

The density of seawater in situ depends also on the temperature and on the pressure, hence the depth. Very important to sonars for instance, as everything influences the sound speed hence can guide the propagation. In a lab, I expect a measure at standard temperature and pressure.