Science Buddies: "Ask an Expert"

I am going to use the question, "How does salt affect the conductivity of water? I know that salt will affect it but how can I make my experiment more interesting/ what other variables could I use?

Hi,

Conductiviity of salt water is an interesting idea:. Here is a Science Buddies Project write up of a related project idea:

https://www.sciencebuddies.org/science- ... p011.shtml

If you are REALLY interested in a more challenging project, look into trying to determine how fast ions travel through solutions. Some resources:

http://en.wikipedia.org/wiki/Molar_conductivity

http://www.currentseparations.com/issue ... s18-3c.pdf

http://wwwchem.uwimona.edu.jm/lab_manua ... xpt19.html

http://ulb.upol.cz/tutorial/conductometry.pdf

http://74.125.155.132/search?q=cache:K_ ... clnk&gl=us

http://74.125.155.132/search?q=cache:hY ... clnk&gl=us


Thiese books could be helpful in investigating these ideas:

http://books.google.com/books?id=Zs9BVp ... ity&f=true

http://books.google.com/books?id=8lANaR ... ty&f=false

http://books.google.com/books?id=dK-HJC ... ty&f=false

http://books.google.com/books?id=sarHIb ... ity&f=true

If you really look into this topic you will find it really fascinating, even worthy of studying as an advanced college student. It is truly an amazing thing to study. So have fun and do a great science fair project!!!

Best regards,

Barrett L. Tomlinson

I have made an alteration to my original experiment. I was going to test the conductivity of water w/ different amounts of salt and the conductivity of a salt solution at different temperatures, Not anymore. Now I am going to test the conductivity 2 different salts dissolved in water at 3 different temperatures and do three trials for each salt. What I need to know is, what salts can I use. I research ones such as, Ammonium nitrate, Magnesium chloride, Potassium chloride, but I am not sure which ones would be safe to use or good to use.

*Is Ammonium Nitrate even a salt?

Thanks

Hello,

What is the easiest or cheapest way to find the conductivity of a liquid. One teacher told me they had probes at my school but they were old and complicated. Another teacher said I could go out and buy a multi-meter but It costs 70 bucks. Are there any other ways?

You should be able to come up with a multi-meter for under $25.

You need to do some research on conductivity. If you do, you will find that the surface area of the electrodes and the distance between them must be used to convert your reading to a conductivity answer with the correct units.

As far as what salts to try, I would use NaCl (table salt) for one of them.

Aluminum nitrate is usually found in a hydrate form (aluminum nitrate noahydrate and others).

You might want to consider the valance of the ions involved in your salt choices. By having mostly Cl- the valance is one for most of your negative ion choices. Sulfates would provide a valance 2 negative ion.

For safety concerns, always look up a MSDS material safety data sheet for the chemicals you are considering and get your advisor's approval. The Wikipedia ususally has MSDS links for common chemicals.

Hey,

When I test the conductivity of the solution with a sulfate wouldn't that create dangerous sulfur gas? I asked my teacher and she agreed so, I'm using NaCl and CaCl2 as my salts.

When I test the conductivity of the solution with a sulfate wouldn't that create dangerous sulfur gas? I asked my teacher and she agreed so, I'm using NaCl and CaCl2 as my salts.

I hate to argue with a teacher, but...
I'd rather risk creating a minor irritating rotten egg sulfer gas than a green poisonous chlorine gas.

Whether there is any possibilty of any gas being produced will depend a lot on the metal electrode material you use, the amount of current involved, and the temperature of the solution.

At room temperature as long as long as you don't choose electrodes that will chemically react on their own with the salt solution, using a nine volt battery to measure conductivity for a few seconds is not likely to produce any free gas with sulfates or chlorides. I would recommend copper wire electrodes as something safe to use with chlorides and sulfates.