Chemical Weathering (Alicia Reyes)

Title: Chemical Weathering: Carbon Dioxide and Acid Rain (6th grade)

Principle(s) Investigated:

• Chemical weathering: carbon dioxide
• Limestone cave formation
• Chemical weathering: acid rain
• pH of various acids

Standards :

S6.2.Topography is reshaped by the weathering of rock and soil and by the transporta­tion and deposition of sediment. As a basis for understanding this concept:

a.Students know water running downhill is the dominant process in shaping the landscape, including California’s landscape.

S6.5.Organisms in ecosystems exchange energy and nutrients among themselves and with the environment. As a basis for understanding this concept:

b.Students know matter is transferred over time from one organism to others in the food web and between organisms and the physical environment.

Materials:

1. vinegar
2. carbonated water
3. soda
4. lemon juice
5. tap water
6. limestone
7. quartz ( you can use a different rock)
8. basalt ( you can use a different rock)
9. 10 pH paper ( each group)
10. 10 sauce cups (each group) ( smart and final)

Procedure: Give a detailed explanation of the procedure and include diagrams if possible.

Big Idea: How does the pH of acid rain and carbonic acids effect and aquatic environment.

Test the pH of different liquids.

1. collect 5 cups
2. place vinegar, soda,lemon juice,club soda and tap water in each cup.
3. Place a strip of pH paper in each solution.
4. Document the pH level of each solution and compare it to the pH reference chart on this website.

extension idea 1: place leaves and rocks in each solution for a 1-3 weeks and document effects.

extension idea 2: pour soil in each solution and plant a seed for a 1-3 weeks. Document the results.

Big Idea: Effects of acid rain and carbon dioxide on rocks.

Test the effects of various pH levels on rocks.

1. collect 10 cups
2. place vinegar, soda,lemon juice,club soda and tap water in each pair of cups.
3. place a piece of limestone in each liquid (5).
4. place a piece of quartz or basalt in in liquid (5) cup.
5. Observe what happens.
6. document your observations.

Student prior knowledge: What prior concepts do students need to understand this activity?

What are some causes of chemical weathering?

Chemical weathering is the process that breaks down rocks through chemical changes. The causes of chemical weathering include the action of water, oxygen, carbon dioxide, living organism, and acid rain.

A closer look at carbon dioxide

Carbon dioxide is a gas found in our atmosphere. It causes chemical weathering. Carbon dioxide dissolves in rainwater and in water that sinks through air pockets in the soil. The result is a weak acid called carbonic acid. Carbonic acid easily weather rocks such as limestone and marble.

CO₂ + H₂O ------> H₂CO₃

Carbon dioxide gas + rain water ------> carbonic acid

How CO2 chemically weathers rocks within the ocean

A SAMPLE OF CHEMICAL WEATHERING OF LIMESTONE

Limestone is mostly made up of the mineral calcite (calcium carbonate). Most limestone was formed on ancient ocean floors, the calcite coming from the shells of marine organisms. Limestone is very soluble, meaning it is easily dissolved. Rain water picks up carbon dioxide in the air and a weak solution of carbonic acid is formed. This water can dissolve limestone over time, creating a cave.

Images of Carlsbad Cavern

Images of Riviera Maya, Mexico Caves (XPLOR)

California locations of limestone caves:California Caverns,Mercer Caverns,Mitchell Caverns, Moaning Cavern, Shasta Caverns

Acid Rain

People have been burning larger amounts of coal, oil, and gas for energy. Burning these fuels can pollute the air with sulfur, carbon, and nitrogen compounds.

Two elements, sulfur and nitrogen, are primarily responsible for the harmful effects of acid rain.

Sulfur is found as a trace element in coal and oil. When these are burned in power plants and industrial boilers, the sulfur combines with oxygen to form sulfur dioxide (SO2). Because SO2 does not react with most chemicals found in the atmosphere, it can travel long distances. Eventually, if it comes in contact with ozone or hydrogen peroxide, it can be converted to sulfur trioxide. Sulfur trioxide can dissolve in water, forming a dilute solution of sulfuric acid.

Nitrogen makes up about 78% of the atmosphere. When heated to the temperatures found in steam boilers and internal combustion engines, it can combine with oxygen from the atmosphere to form nitrogen oxide and nitrogen dioxide (NOx). NOx is the sum of nitrogen oxide and nitrogen dioxide in a given parcel of air. These can dissolve in water, forming weak solutions of nitric and nitrous acids.

• — Compounds from burning coal, oil and gas react chemically with rain water forming acids.
• — Acid rain causes very rapid chemical weathering

The pH scale of reference

Explanation: Give a thorough explanation of the experiment or demonstration. Your explanation should be written to give your fellow teachers a solid understanding and include greater detail than what you might provide for your secondary students. Make certain to include equations whenever pertinent.

How does the pH of acid rain and carbonic acids effect our environments?

Testing the pH of different liquids.

This experiment is to gain a hands on knowledge for pH levels of common liquids we encounter in our lives and compare in what ways the various pH levels have on our biosphere and lithosphere.

extension idea 1: place leaves and rocks in each solution for a 1-3 weeks and document effects.

This extension will help students discover how acid rain can change organic and inorganic matter.

extension idea 2: pour soil in each solution and plant a seed for a 1-3 weeks. Document the results.

The extension will prompt more questions of the effects acid rain can have on plant growth.

Effects of acid rain carbon dioxide on rocks.

Test the pH of different liquids.

During this experiment your students will observe the effects of an acidic liquid on rocks. These chemical reactions weaken the rocks of limestone more frequently than quartz or basalt. You will observe bubbles coming from the limestone rocks. These bubbles are carbon dioxide being released back into the atmosphere, as well as, calcium carbonate, which will settle to the ground.

CaCO3 + 2CH3COOH = Ca(CH3COO)2 + H2O + CO2. Limestone (CaCO3) combined with vinegar (2CH3COOH ) yields calcium acetate Ca(CH3COO)2, water (H20) and carbon dioxide (CO2). This equation shows how each compound is broken and bonded, and the products of the reaction.

Questions & Answers: Give three thought-provoking questions and provide detailed answers.

1. How will acid rain effect forest?

Acid deposition can influence the growth of forest vegetation and soils. Acid rain can weaken trees’ natural defenses. This can effect how they protect themselves from to disease and pests. Acid rain has contributed to the decline of the spruce-fir forests throughout the Eastern United States. Acid rain may remove soil nutrients such as calcium and magnesium from soils in high elevation forests and cause damage to needles of Red Spruce.

2. What effect does carbon dioxide deposition have on the pH of lakes and oceans?

Ocean acidification is effected by chemical compounds such as carbon dioxide, sulfur or nitrogen when they mix with seawater. An increase in these chemical compounds in lakes and oceans can lower the pH and reduces the storage of carbon.

3. How will the pH of an ocean and lake effect living organisms?

The decrease in pH levels can effect how marine organisms--such as sea urchins, corals and certain types of plankton-- use calcium carbonate for making hard outer shells or exoskeletons. These organisms provide essential food and habitat to other species, so their demise could affect an entire ocean ecosystems. Also, if the pH levels in the water decrease to much it could effect the reproduction rate of marine organisms.

Another effect of acid rain can be the loss of fish in acid sensitive lakes and streams. Many species of fish are not able to survive in acidic water. Acid rain affects lakes and streams in two ways: chronic and episodic. Chronic, or long-term acidification results form years of acidic rainfall. It reduces the alkalinity (buffering capacity) and increases the acidity of the water. Chronic acidification may reduce the levels of nutrients such as calcium, which, over time, may weaken the fish and other plants and animals in an aquatic ecosystem. Episodic acidification is a sudden jump in the acidity of the water. This can result from a heavy rainstorm. It also happens in the spring, because the sulfates and nitrates will concentrate in the lowest layers of a snowpack. In the spring, when that snow melts, it will be more acidic than normal. Episodic acidification can cause sudden shifts in water chemistry. This may lead to high concentrations of substances such as aluminum, which may be toxic to fish.

Donald Rice, director of the National Science Foundation (NSF)'s Chemical Oceanography Program, co-funder of the NASA and NOAA states there is strong evidence that carbon dioxide is the culprit globally, even though locally, contamination by strong acids may be primarily responsible for increasing seawater acidity.

Applications to Everyday Life: Explain (don't just list) three instances where this principle can be used to explain other phenomenon.

1. You can use this principle to discover that decaying plants and animals matter are also rich in carbon dioxide CO2. Rain water will collect this carbon dioxide and forms carbonic acids that weather rocks, such a marble. Oven time this will weaken the rocks.
1. The carbonic acid can collect in the ocean from this process, as well as, the increased use of fossil fuels. As a result, students will begin to make connections interrelationships of living organism and their environment.
2. You can use this principle to extend your investigations on the more CO2 that collects in the oceans, the more carbonic acid. Thus pH levels will increase and begin to effect how organism reproduce or whether they live or die. These results, can effect the food web and completely alter the ecosystem.
   1. You can use this principle to make the connection that calcium carbonate is also found in sea shells, as well as, egg shells. This is another extension of how elements are rearranged to form new substances both organic and inorganic. This furthers their understanding that matter is transferred over time from one organism to others in the food web and between organisms and the physical environment.

Photographs: Include a photograph of you or students performing the experiment/demonstration, and a close-up, easy to interpret photograph of the activity --these can be included later.

Videos: Include links to videos posted on the web that relate to your activity. These can be videos you have made or ones others have made.

Videos of acid rain:

http://youtu.be/qmUDpt6Q4eg

Chemical weathering video:

http://youtu.be/6VnVRHIV6j4

Carlsbad cave Video:

http://youtu.be/NDHGCSN5ZRM

Websites of interest:

http://www.adventure-caves-usa.com/cave-formations.html

http://www.nsf.gov/news/news_summ.jsp?cntn_id=109997

For Teachers: A better understanding of how CO2 breaks down calcite ( limestone) as well as the better understanding of pH.

http://www.uh.edu/~jbutler/kunming/carbonates.html

Carlsbad Cavern website

http://www.nps.gov/cave/forteachers/ms_geology.htm

Riviera Maya Cave Environment

http://cenotesoftherivieramaya.com/4caveenvironment.htm

Middle school Lesson Unit: Carlsbad Caverns Geology

http://www.nps.gov/cave/forteachers/upload/geology_ms_surf_carlsbad.pdf