Electric current in liquids
In an ionic bond one atom gives away an electron and becomes a positive ion, another takes it and becomes a negative ion, and they are held by electric attraction; for example, table salt NaCl has Na⁺ and Cl⁻. In water, the water molecules weaken the attraction between the ions and the crystal breaks up into positive and negative ions — this is electrolytic dissociation. Aqueous solutions or melts of salts, acids and bases are called electrolytes, and the current in them is carried by ions. Pure (distilled) water hardly conducts, while ordinary water does because of dissolved salts. The conductors placed in an electrolyte are electrodes: the one connected to the “+” of the source is the anode, the one connected to the “–” is the cathode. Positive ions go to the cathode and negative ions to the anode. Only the teacher performs experiments with solutions; never taste a solution and never connect mains current to water.
Draw a diagram of a solution in a beaker in your notebook: two electrodes, a “+” and “–” source, the anode, the cathode and the ions’ directions with arrows. Do not do a real experiment.