In this activity, students explore the effect of chemical erosion on statues and monuments. They use chalk to see what happens when limestone is placed in liquids with different pH values. They also learn several things that engineers are doing to reduce the effects of acid rain.
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- Colorado: Science
- Common Core State Standards for Mathematics: Math
- 3. Draw a scaled picture graph and a scaled bar graph to represent a data set with several categories. Solve one- and two-step "how many more" and "how many less" problems using information presented in scaled bar graphs. For example, draw a bar graph in which each square in the bar graph might represent 5 pets. (Grade 3)  ...show
- 1. Use a pair of perpendicular number lines, called axes, to define a coordinate system, with the intersection of the lines (the origin) arranged to coincide with the 0 on each line and a given point in the plane located by using an ordered pair of numbers, called its coordinates. Understand that the first number indicates how far to travel from the origin in the direction of one axis, and the second number indicates how far to travel in the direction of the second axis, with the convention that the names of the two axes and the coordinates correspond (e.g., x-axis and x-coordinate, y-axis and y-coordinate). (Grade 5)  ...show
- International Technology and Engineering Educators Association: Technology
- C. The use of technology affects the environment in good and bad ways. (Grades 3 - 5)  ...show
- Next Generation Science Standards: Science
- Make observations and/or measurements to provide evidence of the effects of weathering or the rate of erosion by water, ice, wind, or vegetation. (Grade 4)  ...show
- Give examples of common acids and bases.
- Describe acid rain and chemical erosion and how they affect the environment.
- List several things that engineers are doing to reduce acid rain and its effects.
For each group:
- ½ cup tap water
- ½ cup lemon juice
- ½ cup white vinegar
- 3 pieces white chalk (larger chalk pieces with a flat surface, if possible, these are easier for the students to decorate)
- 3 small cups labeled with group names (clear plastic cups work best)
- 3 nails (or other sharp objects that could scratch chalk)
- 3 strips litmus paper
- 3 copies of the Attack Worksheet and Acid KWL Chart
For the teacher/instructor:
- Waterproof marker
- Watch/clock, stopwatch or timer
Before the lesson
- Gather supplies.
- Prepare three cups for each group, one containing tap water, one with lemon juice and one with vinegar. Clearly label each cup using a waterproof maker with the group name and the liquid each cup contains.
- Make copies of the Attack Worksheet.
With the students
- Pass out Attack Worksheet and Acid KWL chart. Have students fill in "Know" section of KWL chart (optional).
- Discuss how and why acid rain occurs and how acid rain can chemically erode many limestone statues and monuments. Explain that engineers work to stop acid rain by finding cleaner ways to create energy as well as modifying existing technologies (cars, industrial plants, etc.) so that they create less air pollution and acid rain.
- Show pictures of chemical weathering. Explain to students that rain is normally a little acidic to begin with, but sometimes it can become even more acidic because of pollution. The amount of damage that acid rain causes depends on how acidic it is. Also explain that damage can occur with just a little bit of acidity over long periods of time. Have students complete the "Want to Know" section of their KWL charts (optional).
- Pass out the prepared cups of liquid, three nails and three pieces of chalk to each group.
- Have each student use a nail to carve a picture in one piece of chalk. Then, have students draw a picture of their chalk on their worksheets. Tell them the picture does not have to be exact; it can just be a quick sketch.
- When finished, each group member should put their piece of chalk in a container of liquid (as shown on Figure 3: one piece of chalk in each of the cups of water, lemon juice or vinegar) and wait 10 minutes. (Note: it is suggested that the teacher set a timer or stopwatch to monitor the time.)
- While students are waiting, have them measure the pH of each of the three liquids with litmus paper.
- After ten minutes, have students remove the chalk from the liquid and draw a new picture of the changed chalk on their worksheets.
- Finally, students should compare their chalk with the other members in their group and fill out the remainder of the worksheet. Have students complete the "Learned" section of the Acid KWL chart (optional).
- Try leaving the chalk in each liquid longer (or the specific liquid that did not dissolve the chalk).
- Try using more concentrated vinegar or lemon juice.
- What do you know about acids? (Possible answers: it is a substance that has a high pH, often tastes sour, turns litmus paper blue and can break things apart.)
- Can you name any acids? (Possible answers: lemons, vinegar, cola, car battery acid, and hydrochloric acid.)
Activity Embedded Assessment
- What causes acid rain? (Answer: Acid rain happens when air pollution — from fossil fuel-burning plants or cars — chemicals react to form acids in the air. The acids in the air then attach to water molecules and fall as rain or snow.)
- What effects does acid rain have on statues and monuments? (Answer: Acid rain can dissolve away statues, monuments and buildings over time.)
- How do engineers try to clean up acid rain? (Answer: Engineers work to find ways other than burning fossil fuels to get energy, such as electric cars. Engineers also design filters for smoke stacks so less air pollution is released into the atmosphere from industrial factories.)
McGee, Elaine. U.S. Department of the Interior, U.S. Geological Survey, "Acid Rain and Our Nation's Capitol," July 21, 1997, accessed August 5, 2006. http://pubs.usgs.gov/gip/acidrain/
Jessica Todd, Melissa Straten, Malinda Schaefer Zarske, Janet Yowell
© 2006 by Regents of the University of Colorado.
Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
Last modified: February 5, 2016