1. Polarity:
* Water is a polar molecule: This means one end of the molecule has a slightly positive charge and the other end has a slightly negative charge. This creates a "pull" or attraction between water molecules.
* "Like dissolves like": Substances that are also polar, like sugar or salt, can interact with the positive and negative ends of water molecules. This allows the substance to break apart and be surrounded by water molecules, effectively dissolving.
2. Hydrogen Bonding:
* Water molecules form hydrogen bonds: This is a strong type of attraction between the hydrogen atom of one water molecule and the oxygen atom of another.
* Polar substances can form hydrogen bonds with water: This further enhances the ability of these substances to dissolve.
3. Other Factors:
* Temperature: Higher temperatures increase the kinetic energy of molecules, making them move faster and facilitating the breaking of bonds within the substance and allowing for better mixing.
* Pressure: Increased pressure can force more molecules into solution.
Substances that don't mix well with water:
* Non-polar substances: These substances have no separation of charges and are not attracted to water molecules. Examples include oil, grease, and wax. These substances tend to clump together or form separate layers in water.
Key takeaway: The ability of a substance to dissolve in water depends primarily on its polarity and its ability to form hydrogen bonds with water molecules.
