Hydration energy is the amount of heat released as an ionic substance is dissolved and its constituent ions are hydrated, or surrounded by water molecules. The polar water molecules adhere strongly to the ions, with the positive hydrogen ends orienting toward the negative ions and the negative oxygen ends orienting toward the positive ions. In general, the higher the hydration energy is, the more soluble the ionic substance is.Continue Reading
As with other chemical reactions where new compounds are formed or old compounds are broken down, thermodynamic advantage is a large part of whether a reaction takes place spontaneously or not. This means that, in general, any chemical reaction is more likely to occur if it results in a release in energy, as this tends to create a more stable state for the compounds involved. There are cases where this tendency to release energy, the enthalpy of a reaction, is overcome by an increase in entropy, making energetically neutral or even unfavorable reactions occur.
The most familiar example of hydration energy is the dissolution of salt in water. Sodium chloride is the most common salt that people encounter, and it is comprised of ionic crystals of sodium ions and chloride ions. When it is dissolved by water, the water warms up due to the hydration energy released.Learn more about Solutions & Mixtures
Since non-polar substances are held together by weak van der Waals interactions and water molecules use strong hydrogen bonds, the van der Waal interactions of non-polar substances are not strong enough to break the hydrogen bonds of the water molecules. Accordingly, the non-polar substance cannot disperse itself in water.Full Answer >
Oil and water do not mix because the molecules in water are polar, which causes them to be attracted to other water molecules and exclude the oil molecules. When the oil molecules are excluded from the water molecules, they clump together with one another.Full Answer >
Emulsifiers work by acting as a link between water molecules and nonpolar molecules, attracting the water with one end and the emulsified molecules with the other. They are made by bonding fatty acids, which attract hydrophobic substances, to a hydrophilic polar group, which attracts water molecules. Normally, substances like oil and water would separate out, even after thorough mixing, but emulsifiers keep the molecules evenly distributed.Full Answer >
Sodium chloride has a high melting point because of the strong electrostatic attraction between its positive and negative ions; this requires more heat energy to overcome. All ionic compounds have high melting points for this reason.Full Answer >