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Science lesson plan · 6th grade (Year 7 in England) · 45 minutes

Physical, chemical and biological weathering

Earth and rocks

CCSS NGSS.MS-ESS2-1CCSS NGSS.MS-ESS2-2England: KS3 Chemistry: Earth and atmosphere (the rock cycle)

Objective and success criteria

Students will: Physical, chemical and biological weathering.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Weathering and erosion

Leads to: the next skill in this area.

Materials: Rock samples, Hand lenses, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 5 min

  • Quick retrieval from earlier learning (Weathering and erosion). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Which type of weathering is this: tree roots growing into cracks? (physical weathering / chemical weathering / biological weathering) → biological weatheringPrompt: Is it caused by temperature and ice, by a chemical reaction, or by living things?
  2. Which happens quickly rather than over a long time? (a mountain wearing down / a canyon forming / a river valley widening / a landslide) → a landslidePrompt: Some changes to Earth take seconds; others take millions of years.
  3. Which type of weathering is this: iron in rock rusting? (physical weathering / chemical weathering / biological weathering) → chemical weatheringPrompt: Is it caused by temperature and ice, by a chemical reaction, or by living things?

Hook · 5 min

  • Pass round different rocks and ask how each one might have formed.
  • Share the objective: Physical, chemical and biological weathering. Read the success criteria together.

I do: model it · 10 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: Which type of weathering is this: water freezes in a crack, expands and splits the rock?
  • Step 1: Physical weathering breaks rock into pieces without changing its chemicals.
  • Step 2: So the answer is: physical (freeze–thaw, heating and cooling)
  • Answer: physical (freeze–thaw, heating and cooling)
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 10 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. Which type of weathering is this: lichens release acids onto bare rock? (physical (freeze–thaw, heating and cooling) / chemical / biological) → biologicalPrompt: Is a living thing involved? Are new substances formed, or does the rock just break into pieces?
  2. Old gravestones made of marble are often harder to read than those made of granite. Why? (Marble is attacked by tree roots / Marble (calcium carbonate) is chemically weathered by acidic rain / Granite dissolves in rain / Granite is softer) → Marble (calcium carbonate) is chemically weathered by acidic rainPrompt: Which rock reacts with acids?

You do: independent practice · 10 min

  • Students work on the student sheet. Circulate and check the first two answers of every student early.
  • Students who finish: write a question of their own for a partner, with the answer.

The 8 questions are on the student sheet below, with answers in the key.

Exit ticket · 5 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. Weathering and erosion: which statement is NOT true? (Rivers erode their banks and carry sediment. / Weathering only happens over a few days. / Weathering helps turn rock into soil. / Limestone caves form by chemical weathering.) → Weathering only happens over a few days.Prompt: What does water do when it freezes?
  2. What is the difference between weathering and erosion? (They are exactly the same / Weathering breaks rock down where it is; erosion carries the pieces away / Erosion only happens in deserts / Weathering moves rocks to the sea) → Weathering breaks rock down where it is; erosion carries the pieces awayPrompt: One process breaks; the other transports.

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: Weathering and erosion.
  • Use concrete materials: rock samples.
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-6.

Free lesson plan from eurekami.com/lesson-plan-builder

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Physical, chemical and biological weathering

Name

Date

Score/ 8

  1. Question 1

    Which type of weathering is this: iron minerals in rock rust and crumble?

    • A. physical (freeze–thaw, heating and cooling)
    • B. chemical
    • C. biological

  2. Question 2

    In which climate is freeze–thaw weathering most common?

    • A. under the sea
    • B. where temperatures often go above and below 0 °C
    • C. in a tropical rainforest
    • D. in a hot desert that never freezes

  3. Question 3

    Weathering and erosion: which statement is NOT true?

    • A. Weathering helps turn rock into soil.
    • B. Limestone caves form by chemical weathering.
    • C. Weathering only happens over a few days.
    • D. Plant roots can split rocks.

  4. Question 4

    Which type of weathering is this: desert rock heats by day and cools at night until its surface flakes off?

    • A. physical (freeze–thaw, heating and cooling)
    • B. chemical
    • C. biological

  5. Question 5

    Which type of weathering is this: water freezes in a crack, expands and splits the rock?

    • A. physical (freeze–thaw, heating and cooling)
    • B. chemical
    • C. biological

  6. Question 6

    Which agent carries the largest rocks and boulders long distances?

    • A. glaciers (moving ice)
    • B. sunlight
    • C. gentle wind
    • D. rain drops

  7. Question 7

    What is the difference between weathering and erosion?

    • A. Weathering breaks rock down where it is; erosion carries the pieces away
    • B. Weathering moves rocks to the sea
    • C. They are exactly the same
    • D. Erosion only happens in deserts

  8. Question 8

    Old gravestones made of marble are often harder to read than those made of granite. Why?

    • A. Marble is attacked by tree roots
    • B. Granite dissolves in rain
    • C. Marble (calcium carbonate) is chemically weathered by acidic rain
    • D. Granite is softer

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Answer key: Physical, chemical and biological weathering

  1. 1. B. chemical

  2. 2. B. where temperatures often go above and below 0 °C

  3. 3. C. Weathering only happens over a few days.

  4. 4. A. physical (freeze–thaw, heating and cooling)

  5. 5. A. physical (freeze–thaw, heating and cooling)

  6. 6. A. glaciers (moving ice)

  7. 7. A. Weathering breaks rock down where it is; erosion carries the pieces away

  8. 8. C. Marble (calcium carbonate) is chemically weathered by acidic rain