RockLicker · Grade 7 · Lesson 2 of 5

Weathering: Evidence and Variables

Compare model data, identify control conditions and distinguish model breakup from mineral chemistry.

  • Grade 7
  • 55 minutes
  • Worksheet + teacher guidance
Back to Grade 7

What you will learn

Mechanical weathering breaks material without changing mineral composition; chemical weathering changes it. A classroom stand-in can model one action without reproducing all rock behavior.

Words to use

  • control: comparison condition
  • mechanical: physical change
  • chemical: composition change

Evidence for this lesson

Illustrative model: equal starting pieces of non-rock modeling material, same 10 min duration. Still group fragments: 1, 0, 2. Gently tumbled group: 5, 7, 6. Count rule is fragments larger than 2 mm.

Use the supplied record as written; do not invent missing results.

Work through the activity

  1. 10 min · Read the modelThe study uses equal pieces of a soft modeling material, not real rock. One group stays still; the other is gently tumbled under the stated conditions.
  2. 15 min · Summarize trialsFind the range and mean number of detached fragments in each group. Keep the original three values visible.
  3. 20 min · ReasonConnect more detached fragments to modeled physical breakup. Explain why this does not measure chemical weathering or predict a natural rock’s weathering rate.
  4. 10 min · Improve the designSpecify a repeatable fragment-counting rule and a way to keep starting piece size and handling consistent.
RockLicker
GRADE 7 · LESSON 2

Weathering: Evidence and Variables

Draw on the printed sheet or write, type or dictate your response.
Draw on the printed sheet or write, type or dictate your response.
Draw on the printed sheet or write, type or dictate your response.
Draw on the printed sheet or write, type or dictate your response.

Responses stay in this open page only. Print before closing or changing pages; no student record is stored online.

Check your understanding

Counting detached fragments establishes …

Teacher & family guide · answers and assessment

Grade 7 · Weathering: Evidence and Variables

Learning goal: Compare model data, identify control conditions and distinguish model breakup from mineral chemistry.

Expected responses

  1. Handling changed; material, starting dimensions and duration stayed comparable.
  2. Still mean 1; tumbled mean 6.
  3. Physical breakup resembles a mechanical-weathering action; the stand-in is not rock.
  4. A claim about all minerals, chemical reaction or a real geological rate would be unsupported.

Understanding check: physical breakup in the model. The data describe breakup; no mineral chemical measurements were made.

Watch for this misconception

A soft stand-in model cannot establish the weathering rate of a real rock.

Assess the evidence

Look for the observations, calculation or explanation named in the learning goal. Accept accurate drawings and dictated responses. Use the expected responses to discuss reasoning; a correct guess without explanation is a starting point for another conversation.

Adapt and extend

Read prompts aloud, enlarge print or let a partner record the learner’s explanation. Design a consistent minimum fragment size and explain how changing it changes counts.