Weathering

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Objective

SWBAT define weathering and identify types of both physical and chemical weathering

Big Idea

This lesson focuses on the comprehensive idea of weathering, including the distinction between physical and chemical weathering

Lesson Introduction

This lesson exposes students to the types of weathering through some brief videos, explanations, and plenty of examples. We start the lesson with a discussion and overview of what weathering actually consists of, and then watch two videos that present information on both physical and chemical weathering (including information on how they're different). We then finish up with some (as usual!) Regents-based practice problems pulled from some recent state-led Regents examinations  before I have the students take an exit ticket before closing out the lesson. 

Materials Needed:

  • Open-top beaker or glass container
  • Access to Freezer (for freezing water)
  • Limestone or Chalk
  • Citric Acid (you can find this in most supermarkets as a  powder you can mix with water, but acetic acid/vinegar can also do the trick if you can't find it)

[Note: For embedded comments, checks for understanding (CFUs), and key additional information on transitions and key parts of the lesson not necessarily included in the below narrative, please go to the comments in the following document: 7.4 - Weathering (Entire Lesson w/comments). Additionally, if you would like all of the resources together in a PDF document, that can be accessed as a complete resource here: 7.4 - Weathering (Entire Lesson)[PDF]. Finally, students may need their Earth Science Reference Tables [ESRT] for parts of the lesson (a document used widely in the New York State Earth Science Regents course) as well.]

Do Now

10 minutes

Students come in silently and complete the (attached) Do Now. In this case, the Do Now is a review of material and some "hot standards" from Unit 5 (Meteorology) in addition to some needed review on material from the former earlier in the year on density. After time expires (anywhere from 2-4 minutes depending on the type of Do Now and number of questions), we collectively go over the responses (usually involving a series of cold calls and/or volunteers), before I call on a student and ask them to read the objective out loud to start the lesson. 

As a general note, the Do Now serves a few purposes:

  1. It serves as a general review of the previous day's material;
  2. It is a re-activation of student knowledge to get them back into "student mode" and get them thinking about science after transitioning from another content area or alternate class;
  3. as a strategy for reviewing material students have struggled with (for example, using this as a focused review for material that they have struggled with on unit assessments or recent quizzes); and,
  4. It is an efficient and established routine for entering the classroom that is repeated each day with fidelity (I never let students enter the classroom talking. While it may seem potentially severe to have students enter silently each day, this is both a school wide expectation and a key component of my classroom. In many respects, I find that students readily enjoy the focus that starting with a quiet classrooms brings each day).

Video & Notes

20 minutes

The Video & Notes section begins with the first video (link here) from Study Jams. I find the video is helpful in both expounding on the differences between weathering and erosion while also giving students appropriate definitions to differentiate between physical and chemical weathering. While students are watching this first video, I have four questions for them to fill in, which involve defining weathering, erosion, and then providing meanings and examples for both physical and chemical weathering. After the video is complete, I usually give students a minute or two to compare their answers with their seat mates before we jump into the second video in the resource.

The second video (link here) is a Youtube clip that is also posted below:

Ostensibly, the video doesn't seem to have a lot to do with the lesson, and I often pose that same questions to students ("why did we watch this?"). After taking a few responses, I then show them a glass beaker that I've previously filled with water. The night before the lesson, I make a mark with tape where the original water level is on the side of the beaker and then place it in the freezer overnight. When I take it out the next morning, the newly formed ice has expanded from its original water level, which I then present to the classroom. By asking "what's happened here?" - students are able to see that ice actually has a greater volume than liquid water, meaning that frozen ice expands, which is what caused the soda can to explode in the video. When that same liquid water gets into crevices in rocks, it can often do the same thing.

We then discuss how this is an example of physical weathering, and I follow that by showing them the picture on the next page of the Video & Notes resource. They take a few minutes to answer the question, which follows that water, animals, plants, and a variety of substances are capable of causing weathering in rocks. Many students have the belief that rocks are "hard" substances (which they often are!) and aren't capable of readily breaking down, but these processes, sometimes over thousands or millions of years, are capable of wearing away rocks into smaller and smaller pieces.

To demonstrate as a final example, I take out some limestone chips (chalk can also work here!) and some diluted citric acid (you can also use vinegar) and dump the chips into the acid bath. Students can see that there is an immediate chemical reaction that takes place as the limestone begins to bubble and slowly dissolve in the acid bath. This is an example of chemical weathering, which students expound upon by answering the question on the second page of the Video & Notes resource (below the example of the tree root breaking the rock). 

As a final note before starting the practice section, we go through the reference page (located at the end of the Video & Notes section) together. This has a few examples that they've seen in the videos at the start of class, but it also presents information related to the rates of weathering. We particularly hone in on the fact about the relationship between climate and weathering rates. 

Practice

25 minutes

The Practice section in this lesson is, like the vast majority of questions found in all of my classwork and homework, is 100% Regents-based. All of the questions come from prior Regents examinations. Likewise, as I try to generally do with all of my lessons, the questions are mostly organized to get increasingly more difficult and increase in complexity, which is why the harder questions tend to come toward the end. For whatever reason, the Regents loves to ask questions about source regions and air masses, so I truly think the practice is worthwhile, considering this is something they'll see over and over and over again in the future. 

In terms of student work habits, I tend to sometimes make this decision in the moment, and as a response of what I know about the students and how they're processing the material on, but I'll either ask them to work independently, in partners, or (sometimes) give them the option. Usually, before starting practice, we tend to go over some steps for self-help ("What should you do if you're stuck?"), and I might reference a previously used multiple-choice or free response strategy in order to build their skills while simultaneously learning content (as an example - one popular one we always use - "If you aren't sure what the right answer is, see if you can eliminate some wrong answer choices"). I tend to circulate for compliance and then hone in on specific students while they're doing this. 

After about 10 minutes, we go over their responses. Students who finish early are encouraged to work on the exit ticket (resource below) and double-check their responses. We use a combination of strategies (active voting, cold calling, popsicle sticks, volunteers) to go over the responses, where students correct their work and ask any clarifying questions. 

Exit Ticket & Closing

7 minutes

In the last few minutes of class, I have students complete the daily Exit Ticket. For the sake of time, I have students grade them communally, with a key emphasis on particular questions and items that hit on the key ideas of the lesson (Note: This usually manifests as students self-grading, or having students do a "trade and grade" with their table partners). After students grade their exit tickets, they usually pass them in (so that I can analyze them) and track their exit ticket scores on a unit Exit Ticket Tracker. 

After students take a few seconds to track their scores, we usually wrap up in a similar way. I give students time to pack up their belongings, and I end the class at the objective, which is posted on the whiteboard, and ask students two questions:

  • Do you feel that you mastered the objective for the day?
  • Can you reiterate one thing you learned about (in this case, information on weathering and differentiating between physical/chemical weathering, etc.)?

Once I take 2-3 individual responses (sometimes I'll ask for a binary "thumbs up/thumbs down" or something similar), I have students leave once the bell rings.