[pibbman]

Hello,

I am currently doing a lab for our Chemistry I class, and the particular lab that I have a question about pertains to Sodium Polyacrylate, or also known as Super Absorbent Polymer.

Anyways, our lab had us add water to the Sodium Polyacrylate and record the results we witnessed, which is the stuff absorbing up all the water.  We were then instructed to dump the stuff out onto the table and separate them into multiple piles.  We each got a bunch of substances to add to the piles, so we could record the result again.

My particular group picked Sodium Carbonate, Baking Soda (Sodium Bicarbonate), Epsom Salt (Magnesium Sulfate), Lactose and Sucrose.  We noticed that upon adding Lactose and Sucrose to the Sodium Polyacrylate & water combination that nothing happened; however, when we added Sodium Carbonate, Baking Soda and Epsom salt we witnessed what appeared to be the water "leaving" (almost as if melting) the sodium polyacrylate(?)

Now we received the results from the other groups and found that all the following resulted in the water "leaving" action:  Sodium Carbonate, Sodium Bicarbonate, Epsom salt, calcium chloride, sodium chloride and Copper II Sulfate.  The others such as Lactose, sucrose, sand and urea did nothing.

I recognized that the group that resulted in the water leaving were all Ionic compounds, and the rest were just molecular compounds that resulted in nothing.  Now I'm on the last question of my assignment and that is to do a "Claim, Data and warrant" report.  However, I'm not sure if my claim is accurate and is still lacking something.

My Claim

Sodium Polyacrylate is an ionic compound, and when ionic compounds are combined with water, they break down.  In this particular case, they form a gel-like substance with water.  

End Claim.

The claim is obviously not complete because this is where I'm stuck.

My Questions.

1.) My professor told me to look up "How does water affect covalent bonds" to help me solve this, and to much googling I'm still lost.  Could someone explain to me what happens?  I already found that water causes ionic compounds to dissolve.

2.) When Sodium Polyacrylate and Water are combined does it become a molecular compound?  (I'm assuming it does because molecular compounds are apparently commonly associated with being "soft")

My assumption so far is that Sodium Polyacrylate and water results in the Sodium Polyacrylate to break down and form a covalent bond (non-polar I assume), and that when another ionic compound such as Sodium Carbonate is added, the polar property of water instead breaks down the Sodium Carbonate and forms a polar covalent bond with that, and essentially leaves the Sodium Polyacrylate.

Am I lost or just thinking too deeply about this?

Thanks for any help and I apologize for such a long post.

[majorjp]

While Sodium Polyacrylate is does have ionic properties due to the interaction of the O^- and Na⁺ the molecule itself is quite a stable polymer. The polymer group does not break down in water there is merely hydrogen bonding interactions causing the apparent "absorption" of water. The addition of the water solvates the metal salt complex to allow for this interaction to occur. Therefore with the addition of more ionic compound the water will be more attracted to solvate the ionic compound via hydrogen bond interactions rather than with Sodium Polyacrylate. The water nevers forms any colvalent bonds with the sodium polyacrylate.