Table Salt Shrinks the Water

You don’t need to be very careful when you pour salt into a glass full of water. For the first granules of salt you pour in, the salt can shrink the water. That is because the effect of electrostatic force between the ions and molecules. The salt separates to form Na⁺ and Cl^-when dissolved in water. There is an attraction force between Na⁺ and the partial negative end of water molecule and between the Cl^- and the partial positive end of water molecule. Therefore, the total volume of solution decreases when salt is dissolved in water. Though, as more salts are put into the water, total volume will increase eventually, before the solution reaches the saturation point, the volume of solution will still be less than the additional value of the volume of salt and water because the ions of salt will fill in the empty space between the water molecules, like sands filling the space between rocks.

        I find it interesting because usually compressions are applied from outside of the object, but in a molecular scale, a substance can be compressed from inner side of itself.

http://www.answers.com/Q/Why_if_you_slowly_pour_a_handful_of_salt_into_a_totally_full_glass_of_water_it_will_not_overflow

Submitted by Wae Nakayama