Melting Points and Boiling Points of Covalent Compounds
The melting and boiling points of covalent compounds vary widely, and because of this, there are examples of covalent compounds that are solids, liquids, and or gases at room temperature.
Some solids found in food and cooking, including ice and some fats, can be readily melted at room temperature. Other solids require higher temperatures to melt, for example, many of the solid compounds in cheese melt when heated to temperatures above room temperature. Many solids found in food have high melting points and may partially or completely decompose before they reach their melting point. Sugar turns brown as it melts because a chemical change is occurring along with the physical change of melting (changing from a solid to a liquid).
Common liquids have varying boiling points as well. The boiling point of water is 100 °C, so water can be evaporated on the stove. Oils have higher boiling points than water, due to the relatively large size of oil molecules as compared to water. Thus, the process of frying can achieve temperatures higher than the boiling point of water 100 °C.
Some molecules found in food and cooking are gases at room temperature. The gas used to heat a gas stove has a boiling point far below room temperature. Aroma molecules wafting from your food that you can smell are also gases. Hot food tends to have a stronger smell because the increases temperature allows more of these molecules to evaporate and may evaporate additional molecules that were not released at room temperature.
Water Solubility of Covalent Compounds
The water solubility of molecular compounds is variable and depends primarily on the polarity of the molecules involved. Substances that are composed of polar molecules are generally water soluble, whereas substances composed of nonpolar molecules are generally insoluble in water.
This page is based on “Chemistry 2e” by Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson, PhD, Openstax which is licensed under CC BY 4.0. Access for free at https://openstax.org/books/chemistry-2e/pages/1-introduction
This page is based on “The Basics of General, Organic, and Biological Chemistry” by David W Ball, John W Hill, Rhonda J Scott, Saylor which is licensed under CC BY-NC-SA 4.0. Access for free at http://saylordotorg.github.io/text_the-basics-of-general-organic-and-biological-chemistry/index.html