As NaCl is added to distilled water, the ionic bond between the sodium ion (Na+) and chloride ion (Cl-) gets broken apart. Water molecules are considered polar, so the H side is more positively charged, whereas O is more negatively charged. As Na+ is brought close to O- and Cl- is brought to H+, the NaCl salt dissolves in the solvent. Adding salt to the water merely changes the density of the solvent, as the mass of the liquid increases with a fixed volume. Due to this, the density of the beads ends up being less than the density of the water. This causes the blue beads to float up. However, the beads is also more dense than the alcohol, causing the white beads to float downwards, causing both of the beads to meet in the middle. It is also important to note that the volumes of the two liquids must be equal in volume, with the top half being the alcohol and the bottom half being salt water.