Many things in nature have chemistry behind them. For some of these things, one would have never thought chemistry was involved. One of these natural events that occur because of chemistry is sinkholes! The biggest question is, how do sinkholes form? Sinkholes form when groundwater starts to erode the limestone in the ground, therefore dissolving the limestone. Under the presence of an acid, limestone is very soluble. Once the limestone is dissolved, the surface does not have any stability and collapses, making a sinkhole. What makes this process part of chemistry is how the limestone dissolves. It dissolves because of solubility. The definition of solubility is,"The quantity of a particular substance that can dissolve in a particular solvent." In this case, the solvent is the rain water. Since limestone is very soluble under the presence of an acid, it will eventually disappear in an area with lots of rain. Rain is naturally acidic because CO2 mixes with the rain to make Carbonic Acid, which has a pH of 5-6. This is low, but whenever it comes in contact with limestone, the slightly acidic property dissolves it. Limestone, known as CaCO3, dissolves into Ca+2 + CO3-2. When the limestone turns into these two aqueous solutions, they dissolve very easily into water, washing the limestone components away. Whenever the limestone is all gone, there is a hole with no stable ground, which then collapses in and creates a sinkhole. Limestone will dissolve even faster if it comes in contact with Acid rain. Acid rain forms when rain mixes with sulfur or nitrogen, which comes from the burning of fossil fuels. Rain mixes with sulfur to create sulfur dioxide, and then sulfur trioxide. It also can create a nitrogen oxide with nitrogen. The pH of this is 4-5, making it more acidic than typical rain water, thus dissolving limestone faster.
"Solubility Basics - What Is Solubility?" What Is Solubility? Why Do Some Things Dissolve and Some Not? N.p., n.d. Web. 03 Jan. 2013.