Boxi Learn › Chemistry › Stage 4 · Systems and Argument
Why salt water carries a current and sugar water doesn't
Salt dissolves as NaCl molecules, and a solid salt crystal conducts because it is made of ions.
Salt is built of charged ions that come apart and move freely when it dissolves or melts; sugar dissolves as whole neutral molecules, so nothing carries the charge.
A friend says salt dissolves into tiny NaCl molecules, and that a dry salt crystal should conduct because it is made of ions. Use what the bulb did with dry salt, salt water and sugar water to explain what is wrong with both ideas.
Sprinkle a few grains of salt and of sugar on a dark plate and look with a magnifier: salt grains are little cubes. Stir a spoon of each into warm water in two saucers and leave them somewhere warm for a few days. What shape comes back from the salt water?