Polar Molecules:
* Ionic compounds: These are held together by electrostatic forces between positively and negatively charged ions. Water's polarity allows it to surround and separate these ions, breaking them apart. Examples include table salt (NaCl), sugar (sucrose), and many salts.
* Polar covalent compounds: These share electrons unequally, creating a partial positive and partial negative charge within the molecule. Water's polarity interacts with these charges, forming hydrogen bonds and allowing them to dissolve. Examples include ethanol, glucose, and many organic acids.
Nonpolar Molecules:
* While water is primarily good at dissolving polar molecules, it can dissolve some nonpolar molecules to a limited extent. This is due to the weak interactions called London dispersion forces, which are temporary fluctuations in electron distribution that can lead to weak attractions. Examples include oxygen gas (O2), nitrogen gas (N2), and some small hydrocarbons.
Factors Influencing Solubility:
* Polarity: As mentioned above, the more polar a molecule is, the more soluble it will be in water.
* Temperature: Increasing temperature generally increases solubility, as molecules have more energy to overcome attractive forces and dissolve.
* Pressure: Pressure has a greater effect on the solubility of gases in liquids than on the solubility of solids.
* Intermolecular forces: The strength of the forces between water molecules and the solute molecules influences solubility.
Examples of Molecules Water Dissolves:
* Sugars: Like sucrose, glucose, and fructose, are polar molecules and readily dissolve in water.
* Salts: Many salts, such as sodium chloride, dissolve in water, forming ions.
* Acids and Bases: Many acids and bases are polar molecules and readily dissolve in water.
* Alcohols: Ethanol and other alcohols are polar molecules that dissolve well in water.
It's important to remember that some molecules are not soluble in water, even if they are polar. For example, oil and water do not mix because the nonpolar oil molecules are not attracted to the polar water molecules.
