oceanography (1 Viewer)

[Timmay]

is there anyone that does (or did) the oceanography option in earth and enviro science that performed a first hand investigation on "the order of precipitation of salts in a cooling solution"

i dont understand how a salt will precipitate whilst cooling? wouldnt it be more logical to be heating a solution and salts would precipitate out which you then seperate and test the salt to discover what it is. (my teacher told me this is beyond the scope of the course though)

so basically i was given the order that a salt will precipitate out and told that this is an idiotic experiment (im inclined to agree) but how would i say that in a 6 or 8 mark question that asks to outline the procedure

 

[midnight]

My class hasn't actually done any of the investigations for oceanography. I haven't looked through the past papers to see what types of questions they ask, as to whether we need to know pracs in detail, I'll have to make it my priority before the exam.
Anyway, I can't see what relevance that has to the course? My teacher told us that we shouldn't stress about the practical parts, and that in general it's something that we've done in junior science, so to try to remember or just make it up.

I checked my textbook and the prac in it involves normal water, salty water, ice cubes and food colouring. Interesting. I'll check it out further and post again if I make any sense of it.

Meanwhile, I really dislike oceanography. It's more difficult than the rest of the topics!

 

[Timmay]

yeah im not a big fan of it... it sounded cool "oceanography" but its mainly a lot of plate tectonics...

we did an experiment with the ice cubes and coloured water that went like

fill a beaker with normal water, add icecubes that have been frozen with food dye and observe (ice cube melts and u can see the colder water with the food dye in it sink to the bottom)

then we filled another beaker of water and added (carefully) a few mls of coloured hot water, the hot water floats on the surface then slowly sunk 2 the bottom

then we filled another beaker and added salty water (with food dye) u can see the salty water sink (because its denser)

anyways thats applicable cos it explains how the deep ocean currents are powered by different densities in the water (cold water being more dense than warm, salty more dense than less salty)

but the precipitation of salts? i dunno...

 

[midnight]

I think I've figured it out - by precipitation they just mean that the salt sinks to the bottom? I don't get the whole 'precipitate out' factor.
And therefore the experiments you did [I'm going to do them tomorrow, I think, I just have to make the ice cubes] do show that.
One thing though: shouldn't the food dye represent the salinity of the water? Otherwise you're doing too many variables, you're meant to test one at a time. And so in my opinion, if you just did the hot and cold unsalty water you're doing te right thing. What it shows is that the warm salty water warms the water around it, and then cools and takes the salts with it to the lower level.

And yeah, I now understand how it's a model of the global conveyor.

 

[Dougie]

it's just a matter of the salt being absorbed more when the water's hotter. everythin else u need to say u can ramble on about, like the whole course. i can't believe the top mark in last yr in the hsc was only 89%. how could u not get over 90% if ur top? esp. in EES!

 

[midnight]

If you say so.

And three people at my school last year got band 6 marks, so I highly doubt that the highest mark in the state was 89%.

 

[Dougie]

top of the state was a friend of a friend of mine. the bands seperate so there r ppl in every band, not just the mark.

 

[midnight]

Oh sorry. I didn't realise you meant that your friend had their raw mark.
I can't speak for everyone, but I find the multiple choice section is where I lose a lot of my marks. Either I'm really stupid or they're quite complicated questions.

If anyone is still around who did that experiment, or if you read this Timmay: I did the first two parts today and the ice cube water slowly turned blue, whereas the hot water one quickly turned blue. That was meant to happen?
I've been doing experiments modelling it over the last week and I always put way too much food dye in, so the water turns completely blue. But other people have given me the impression that that's not meant to be the case?

Argh.
I think there's a good chance that this will be our experiment for the option, since they've asked for the other major ones already.