1. In a glass beaker, take small amount of solid sodium chloride.
2. Dip two graphite rods (electrodes) in the solution. 3. Connect these rods to a battery through a bulb and a switch.
4. Switch on the battery. The bulb will not glow. This show that no current has passed through the solid sodium chloride.
5. Now, add some water to the salt so that it may dissolve.
6. Repeat the operation. The bulb will immediately glow showing that current has passed through the salt solution.
Explanation. Sodium chloride (NaCl) is a crystalline solid and the current is carried by the mobility (movement) of ions. Since the ions do not move in the solid state, the salt is not conducting. In aqueous solution, both `Na^(+)` and `Cl^(-)` ions can move and the salt will be conducting in the solution. That is why the bulb glows.
