What is Weathering and How Does It Affect Rocks?
The set of physical, chemical, and biological processes that change soil or rocks’ physical and chemical states are called
weathering
. When rocks are decomposed, dissolved, or become loose by way of chemical processes and turned into residual materials, this is known as
chemical weathering
. The best way to describe how weathering works is that the bonds holding the rock together are broken down by chemical reactions. These chemical reactions cause the rock to break down and turn into smaller piece, which repeats itself and the rock gets even smaller. When the rock is much smaller,
erosion
happens. Erosion is when these smaller pieces of the rock are taken away and end up in another area.
In areas with quite a bit of water, chemical weathering is seen a lot more. That’s because water is needed for a lot of chemical reactions to be completed. In this experiment, you’ll be learning about how carbonic acid is formed by carbonation weathering. When this process happens, carbon dioxide in rainwater or in other water forms carbonic acid. Carbonic acid makes some rocks soft which makes the erosion process much quicker.
Question
What effect does carbonation, a type of chemical weathering, have of different rock samples?
Materials
- Masking tape
- A package of plastic 8 oz cups
- 3 pieces of these rock types: limestone, marble, granite, and sandstone
- 1-liter bottle of seltzer water or club water (either one works)
- A source of tap water
- Permanent marker
Procedure
- Take four of the plastic cups and fill them ¾ of the way full of your club soda or seltzer water.
- Take the other four cups and fill them ¾ of the way full with tap water.
- Take your masking tape and marker, then label the cups: “limestone and tap water”; “limestone and carbonated water”; “marble and carbonated water”; “marble and tap water”; “granite and carbonated water”; “granite and tap water”; “sandstone and carbonated water”; and “sandstone and tape water”.
- Once you have your cups labeled, place the appropriate piece of stone into the cup. You should have one piece left over from each type of rock. This will be your Control example.
- Let your cups sit for about 4 days.
