Solution Solvent acting to dissolve a SOLUTE

The extracellular (eks-trah-SELL-you-lar) fluid lying ''outside'' (extra-) of our body's ''little cells'' (cellul), is one type of inorganic saline solution. The major solvent dissolver is the water molecule, H2O. The chief solute in the extracellular fluid is sodium chloride, NaCl.

Molecule 2

Molecule 2

Sodium chloride (NaCl), or common table salt, occurs as a solid cube. Figure 4.2 shows how the + charges of Na+ solute are attracted to the negative (—) charges on the O2— of many H2O molecules. Likewise, the negative (—) charges of Cl— are attracted to the positive (+) charges of the H+ poles or ends of the surrounding water molecules. Therefore, sodium and chloride split apart from each other and become individual Na+ and Cl— ions (EYE-ahns). An ion is simply an atom that has either an excess or deficiency of outermost electrons, so that it is electrically charged.

Electrolyte functions of ions

NaCl is a well-known electrolyte (ee-LEK-troh-light). An electrolyte is a substance that ''breaks down'' (lyt) into ions when placed into water solvent,

Atom 3

Atom 3

NaCl cube "breaks down"

Fig. 4.2 A saline solution results from the action of H2O upon NaCl.

NaCl cube "breaks down"

Fig. 4.2 A saline solution results from the action of H2O upon NaCl.

such that the resulting solution can conduct an "electrical current'' (electro-). The saline solution surrounding our body cells, then, is full of electrolytes and H2O molecules with positively-charged H+ poles. It is the body's inner sea. And, like the sea, it conducts an electrical current. This is because the negatively-charged electrons flowing in an electrical current are attracted to the many positively-charged areas within the extracellular fluid. Because of this seawater-like structural arrangement, you now know why your mother told you to get out of the water during a thunderstorm!

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