Water Quality B/C

[goodgra1]

Thanks

[Fastsailor]

Looking for confirmation on the mass/volume % usage in the Water Quality rules (and Density Lab). Do I assume correctly that this 1-10% value is (mass of solute in grams / volume of solution in mL ) x 100 ?

Quote from rules:

"Teams must build, calibrate, bring and demonstrate a salinometer/hydrometer capable of measuring saltwater (most likely NaCl) concentrations between 1-10% (mass/volume)."

Here is an interesting comment from wikipedia on the "incorrect" use of mass/volume percentage:

In biology, the "%" symbol is sometimes incorrectly used to denote mass concentration, also called "mass/volume percentage." A solution with 1 g of solute dissolved in a final volume of 100 mL of solution would be labeled as "1%" or "1% m/v" (mass/volume). The notation is mathematically flawed because the unit "%" can only be used for dimensionless quantities. "Percent solution" or "percentage solution" are thus terms best reserved for "mass percent solutions" (m/m = m% = mass solute/mass total solution after mixing), or "volume percent solutions" (v/v = v% = volume solute per volume of total solution after mixing). The very ambiguous terms "percent solution" and "percentage solutions" with no other qualifiers, continue to occasionally be encountered.

https://en.wikipedia.org/wiki/Mass_conc ... chemistry)

[MattChina]

That is a very interesting point. I think it would be mass in grams over volume in mL, but again, I dont run water quality, so maybe email like soinc or an event proctor for clarification.

[NadiaT]

Do we need to know about estuaries? If so, how much? I was initially under the impression that we didn't, as estuaries are either marine or brackish water, not fresh, but it came up on a practice test we took. Is this a fluke or will it come up more often? Thanks.

[MattChina]

Do we need to know about estuaries? If so, how much? I was initially under the impression that we didn't, as estuaries are either marine or brackish water, not fresh, but it came up on a practice test we took. Is this a fluke or will it come up more often? Thanks.

No, estuaries are part of water quality this year, maybe the practice test you took was from previous years when this event was run.

[kate!]

Do we need to know about estuaries? If so, how much? I was initially under the impression that we didn't, as estuaries are either marine or brackish water, not fresh, but it came up on a practice test we took. Is this a fluke or will it come up more often? Thanks.

You should know what an estuary is, but not really any more information, since the topic is exclusively freshwater.

[NadiaT]

Do we need to know about estuaries? If so, how much? I was initially under the impression that we didn't, as estuaries are either marine or brackish water, not fresh, but it came up on a practice test we took. Is this a fluke or will it come up more often? Thanks.

No, estuaries are part of water quality this year, maybe the practice test you took was from previous years when this event was run.

Thank you!

[NadiaT]

Do we need to know about estuaries? If so, how much? I was initially under the impression that we didn't, as estuaries are either marine or brackish water, not fresh, but it came up on a practice test we took. Is this a fluke or will it come up more often? Thanks.

You should know what an estuary is, but not really any more information, since the topic is exclusively freshwater.

Thank you!

[jimmy-bond]

Does anyone have an efficient way to distinguish horse fly larvae from deer fly larvae? It has been costing me a few points on tests.

[sourpatchkids]

Having salinometer issues again lol. Is it just my salinometer that has its marks for 1-10% in an extremely small section of an approx 13cm straw? I used the directions from soinc to make the simplest salinometer possible. How can I make my salinometer in a way that allows these marks to be more spread out?