The Four Main Properties of Water
- Surface tension
Surface tension is the tension of the surface film of a liquid caused by the attraction of particles in the surface layer by the bulk of the liquid, which tends to minimize surface area.
Cohesion is the tendency of molecules to stick together and resist spreading. This is of the same substance.
Adhesion is when water sticks to other molecules it is attracted too.
Why does water form a dome on a penny?
Water forms a dome on a penny because of surface tension, the surface tension is produced by a force of attraction between water molecules.
Polarity is having poles or being polar. Water is a polar molecule is because there is a uneven distribution of electron density.
Is salt and cooking oil a polar or non-polar substance?
Salt is a polar substance which is the reason why it dissolves in water, because polar molecules dissolve other polar molecules. Cooking oil is however non-polar, which is the reason it does not dissolve in water and separates from water when in water.
Two real world examples:
An example of cohesion is rain. If cohesion did not exist than the rain would fall as individual water molecules instead of drops of water. During cohesion, water is attracted to itself which is why it turns molecules into raindrops.
Polar and non-polar molecules can be seen when you make Italian dressing. In Italian dressing some of the main ingredients include water, vinegar, and oil. After making the dressing, if it has been sitting unused for a while you can see that the oil has separated from the water and vinegar. This is because water and vinegar are polar while oil is non-polar. Therefore, they can cannot be combined.