Water forms a dome-shaped bubble above the penny because the water molecules are sticking to one another, also called cohesion.
When you add soap to the penny, the soap effects the cohesion of the water. The amount of drops on a regular penny are significantly higher than the penny with soap. The water on the penny takes the shape due to surface tension. Trial 1 for the regular penny there was 30 drops of water. The penny with the soap only had 12 drops.
Salt is a polar substance, while cooking oil is a non-polar substance. Salt is dissolves in water, but cooking oil just sits at the top.
These properties of water are very significant to life. Due to high surface tensions, animals can use water as their habitat, it also allows insects to travel on water without sinking. Cohesion is important because it hold hydrogen bonds together, which creates surface tension, while adhesion pulls water towards other molecules.
Credits:
Created with images by bella67 - "drip drop of water wave" • the3cats - "oil in water oil eye liquid"