There are a wealth of good weathering labs that teachers have already created and posted online. I don’t believe in re-inventing the wheel; I’d rather spend my time and energy on things that will measurable benefit my students. For this series of weathering experiments, I start out using a fairly standard, non-inquiry lab that I found on the internet. It models physical and chemical weathering using sugar cubes and Alka Seltzer tablets. However, I take it further by having students go on to design and carry out their own experiments about weathering. In my experience, the most challenging thing about having students design weathering experiments is ensuring that there are sufficient supplies available – all too often, a good idea is stymied because we don’t have the necessary items on hand. For this lab, I have found it is most critical to have a decent selection of smallish rock samples, with particular emphasis on soft, easy to weather, specimens. Vinegar and baking soda (to manipulate pH) are also indispensable.
One important teaching note: for me, this lesson comes towards the end of the year. At that point in the year, my students have a reasonable amount of experience designing experiments and going through the peer review process. If these lessons were at the beginning of the year, I would scaffold the process much more carefully.
Weathering of Rocks, Day 1:
• Do Now: Look at the photograph worn stone steps. What do you think caused the steps to develop the dip at the center?
• Check homework: Randomly call on students to read the reflections they wrote on their classmates presentations from the previous class.
• Discuss the Do Now. How permanent are rocks? What wears them down? What would make a rock wear more quickly or slowly?
• Randomly divide the class into lab groups.
• What is the difference between chemical and physical weathering? Discuss likely distinctions and try to find examples of each in students’ prior knowledge.
• Give students time to read through the guided experiment worksheet. http://www.northwestern.k12.oh.us/userfiles/231/Classes/5543/Weathering%20Lab.pdf Show where the supplies are and give time for questions.
• Allow students time to do guided experiments, draw graphs, and answer questions.
• Discuss the results of the experiments. What were some of the experimental strengths and weaknesses? What can we learn about real weathering from these experiments? What are some questions you still have about weathering?
• Design an experimental procedure to investigate some aspect of weathering further. This procedure should be practical to carry out in class. Remember to include an experimental question, hypothesis, materials list, control, procedure, and blank data chart.
Weathering of Rocks, Day 2:
• Do Now: Write an explanation of the difference between weathering and erosion. Look in a dictionary or textbook if necessary.
• Check homework: Circulate during the Do Now to visually check that students have completed homework.
• Discuss the Do Now: Call on several students randomly to explain the difference between erosion and weathering.
• Randomly divide the class into lab groups.
• Share the experiment you designed for homework with your lab partner(s). Within your group, decide which experiment you would like to carry out. Refine the procedure. Be prepared to share your procedure with the class.
• Review what constructive criticism looks like.
• Have each lab group present their experimental question, hypothesis, control, and procedure. As a class, give feedback and constructive criticism.
• When all lab groups have presented, give students time to revise their procedures (if necessary) and carry out their experiments.
• Share experimental results with the class. What do these experiments suggest about weathering in the outside world? What further experiments could we (theoretically) do to learn more?
• Read Ch. 5 “Weathering, Soil, and Mass Movements” of textbook. Questions #1-10 p.153
Sugar cubes, bottles with caps, hot water, cold water, alka seltzer, scales, thermometers, beakers, stop watches, “Weathering Lab” handout, assorted materials for inquiry experiments (vinegar, baking soda, various rock samples, sand, gravel, pH paper, fine iron wool, etc.)
Anderson, Andy. Steps of St. Hripsime Armenian Apostolic Church in Etchmiadbin, Armenia. Digital image. N.p., n.d. Web. 18 Aug. 2015. <http://theorthodoxchurch.info/blog/news/2012/04/22/remembering-genocide-and-faith-at-geghard-monastery-in-the-mountains-of-armenia/>.
Tarbuck, Edward J., Frederick K. Lutgens, and Dennis Tasa. Prentice Hall Earth Science. Needham, MA: Pearson/Prentice Hall, 2006. Print.
“Weathering Lab.” SpringerReference (2011): n. pag. Web. 18 Aug. 2015. <http://www.northwestern.k12.oh.us/userfiles/231/Classes/5543/Weathering%20Lab.pdf>.