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9.2: Lesson 9.1: Weathering

Difficulty Level: At Grade Created by: CK-12

Key Concepts

  • Definition of weathering
  • Mechanical weathering
  • Chemical weathering
  • Rates of weathering

Lesson Objectives

  • Define mechanical and chemical weathering.
  • Discuss agents of weathering.
  • Give examples of each type of weathering.

Lesson Vocabulary

  • abrasion: form of mechanical weathering that occurs when rocks and rock particles scrape against other rocks
  • chemical weathering: type of weathering that changes the mineral composition of rocks
  • erosion: transport of weathered material by water, wind, ice, or gravity
  • ice wedging: form of mechanical weather that occurs when water enters a crack in rock, expands as it freezes, and wedges the rock apart
  • mechanical weathering: type of weathering that breaks rocks into smaller pieces without changing their mineral composition

Teaching Strategies

Introducing the Lesson

Use the PowerPoint slide presentation at the URL below to introduce students to weathering. The slides alternately present and answer basic questions about the topic. In addition to introducing lesson content, the questions will allow you to assess what students already know before they start studying the chapter. You can revisit the slides at the end of the lesson as a quick review of lesson content.



Have students play the weathering and erosion game at the following URL. In the game, they will explore how different agents of erosion change the landscape and the time spans they take to bring about observable changes.


Building Science Skills

Set up one or more of the stations described in the PDF documents below. At each station, students will investigate a different aspect of weathering, including weathering by wind (station 1), dissolving rock (station 3), mechanical weathering (station 4), and/or chemical weathering (station 5). The last URL below is a student handout that contains background information and answer sheets for all of the stations.

Differentiated Instruction

Ask a pair or small group of students to add the word weathering to the word wall. On a large index card, they should write the term and its definition. They should also include separate definitions of mechanical weathering and chemical weathering, with examples of each type.


Ask a small group of students to use the following Web site to organize a class game of weathering-and-erosion jeopardy. One of the students should act as the MC. The Web site includes questions and answers weighted by difficulty with different amounts of money awarded for correct answers. Suggest that the students use play money to reward players who answer questions correctly.


Science Inquiry

In the inquiry activity at the URL below, students hypothesize the effects of water and dilute hydrochloric acid on limestone. Then they devise an experiment to test their hypotheses. Relate the results of their experiments to the acceleration of chemical weathering by acid rain.


Common Misconceptions

Students often confuse the terms weathering and erosion and may consider them to mean essentially the same thing. As a result, they often use the words interchangeably. Make sure your students know the difference between these two related processes. Stress that weathering breaks down rock but does not involve transport of the sediments. The latter is the work of erosion, which moves but does not break down rock. You can demonstrate the difference between weathering and erosion with the excellent 5-minute activity “Erosion and Weathering in My Mouth” (activity # 20) at the following URL.


Reinforce and Review

Lesson Worksheets

Copy and distribute the lesson worksheets in the CK-12 Earth Science for Middle School Workbook. Ask students to complete the worksheets alone or in pairs to reinforce lesson content.

Lesson Review Questions

Have students answer the Review Questions listed at the end of the lesson in the FlexBook® student edition.

Points to Consider

What types of surfaces other than rock are affected by weathering?

What might the surface of Earth look like if weathering did not occur?

Do you think that you would be alive today if water did not dissolve elements?

Would the same composition of rock weather the same way in three very different climates?

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