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Help-My son has a chemistry question


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And I don't know the answer. We haven't been able to find it either.

 

When table salt (NaCl) dissolves in water, it is caused by the positive and negatively charged water molecules pulling apart the sodium and chloride ions. So if the salt comes apart, and sodium and chloride are poisons on their own, how does salt water not become poison water? It still tastes salty, so it retains the properties of salt, yet the salt molecule has pulled itself apart. Is there something we are misunderstanding about this? Please help if you know the answer!

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Here is what I found....

Salt water is not full of "sodium chloride." Instead it is full of sodium and chlorine. The atoms are not poisonous and reactive like sodium metal and chlorine gas because they are electrically charged atoms called "ions." The sodium atoms are missing their outer electron. Because of this, the remaining electrons behave as a filled electronic shell, so they cannot easily react and form chemical bonds with other atoms except by electrical attraction. The chlorine has one extra electron and its outer electron shell is complete, so like sodium it too cannot bond with other atoms. These oppositely charged atoms can attract each other and form a salt crystal, but when that crystal dissolves in water, the electrified atoms are pulled away from each other as the water molecules surround them, and they float through the water separately.

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Does this help?

 

http://www.newton.dep.anl.gov/askasci/chem00/chem00297.htm

 

I think in a nutshell what it's saying is that the Na+ and Cl- ion become bound to the water molecules. When the water is evaporated off, they join up with each other again.

 

That being said, too much salt water IS poisonous. Our bodies need lots of things in small or trace amounts that would kill us if given in large doses.

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but when that crystal dissolves in water, the electrified atoms are pulled away from each other as the water molecules surround them, and they float through the water separately.

 

Not quite

The sodium and chloride ions are actually attracted to the positively and negatively charged parts of the water molecule and become attached to it. The O end of the water is negatively charged attracting NA+ ions, and the H portion is positively charged attracting Cl- ions.

 

Another thing to keep in mind is that these molecules all have thermal energy and are constantly moving (solids less than liquids less than gases) as are their electrons. Weak bonds can break and reform. The reactions can go back and forth. They look very final on paper but are not in the salt water.

 

Smart son to be asking that question! Keep up the good work!

Edited by Adrianne
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