Summary of Lessons So Far
Water has many properties that are critical to maintaining life. Generally, it is a polar molecule, allowing for the formation of hydrogen bonds. Hydrogen bonds allow ions and other polar molecules to dissolve in water. Therefore, water is an excellent solvent.
The hydrogen bonds between water molecules cause the water to have a high heat capacity. This means it takes a lot of added heat to raise its temperature. As the temperature rises, the hydrogen bonds between water continually break and form anew. Thus, this allows for the overall temperature to remain stable, although the system gets additional energy.
Water also exhibits a high heat of vaporization. As a matter of fact, this is key to how organisms cool themselves by the evaporation of sweat. Water’s cohesive forces allow for the property of surface tension, whereas its adhesive properties are seen as water rises inside capillary tubes.
The pH value is a measure of hydrogen ion concentration in a solution. It is one of many chemical characteristics that is highly regulated in living organisms through homeostasis. Acids and bases can change pH values, but buffers tend to moderate the changes they cause. These properties of water are intimately connected to the biochemical and physical processes performed by living organisms, and life would be very different if these properties were altered, if it could exist at all.
Glossary of Words
molecule that donates hydrogen ions and increases the concentration of hydrogen ions in a solution
attraction between water molecules and other molecules
molecule that donates hydroxide ions or otherwise binds excess hydrogen ions and decreases the concentration of hydrogen ions in a solution
substance that prevents a change in pH by absorbing or releasing hydrogen or hydroxide ions
amount of heat required to change the temperature of one gram of water by one degree Celsius
occurs because water molecules are attracted to charges on the inner surfaces of narrow tubular structures such as glass tubes, drawing the water molecules to the sides of the tubes
intermolecular forces between water molecules caused by the polar nature of water; responsible for surface tension
release of an ion from a molecule such that the original molecule now consists of an ion and the charged remains of the original, such as when water dissociates into H+ and OH–
Heat of vaporization of water
describes ions or polar molecules that interact well with other polar molecules such as water
describes uncharged non-polar molecules that do not interact well with polar molecules such as water
(also, pH paper) filter paper that has been treated with a natural water-soluble dye that changes its color as the pH of the environment changes so it can be used as a pH indicator
see litmus paper
scale ranging from zero to 14 that is inversely proportional to the concentration of hydrogen ions in a solution
substance capable of dissolving another substance
Specific heat capacity
the amount of heat one gram of a substance must absorb or lose to change its temperature by one degree Celsius
Sphere of hydration
when a polar water molecule surrounds charged or polar molecules thus keeping them dissolved and in solution
tension at the surface of a body of liquid that prevents the molecules from separating; created by the attractive cohesive forces between the molecules of the liquid