Junior Science: Rock Cycle and Earth Resources Tutor Prep Guide | Three Clues, Five Steps, Four Common Errors

2026-11-14

Tutor lesson-prep guides · Junior Science

Show a student a rock and the answer is hard and grey; ask where it came from and the answer is silence. The chapter rests on two ideas: rocks fall into three groups by how they formed, and any rock can be moved, buried and heated into another group. Once a student asks which step of the cycle a rock is on, the names stop being memory work.

Objectives — Students can: (1) classify a rock as igneous, sedimentary or metamorphic from grain size, layering and fossils; (2) describe a complete path from magma to sedimentary rock and name the process at each step; (3) give two rocks found in Hong Kong and explain how weathering and erosion shape the landscape, linking this to how resources form.

01 Prerequisites (3-minute check)

If any of these fails, fix it before the lesson starts.

Skill	Quick check	Pass mark
States of matter	Is magma cooling to solid a change of state or a chemical change?	A change of state, no new substance
Particle model	Does faster cooling give larger or smaller crystals?	Faster cooling gives smaller crystals
Landscape observation	Where does the loose debris on a hillside come from?	Rock broken down by weathering

02 Lesson flow (60 minutes)

Time	Stage	Tutor does	Student does
0-6 min	Two rocks on the bench	One granite, one sandstone	Write which one you think formed in water
6-20 min	Three clues	Grain size, layering, fossils	Give one reason for each rock
20-34 min	Five steps	Magma, cooling, weathering and transport, burial, melting	Draw the path from magma to sedimentary rock
34-46 min	Weathering and erosion	Two physical and two chemical examples, then sort them	Decide which word fits each event
46-56 min	Local examples and resources	Hong Kong rocks and building materials	Name one resource and one limit on it
56-60 min	Exit check	Collect two questions and mark at once	Complete independently

03 Teaching script (read it out)

Scene 1: Three clues: grains, layers, fossils

Do not start with geological periods. Hand over three rocks and ask three questions only: are the grains large and interlocking, or rounded and layered? Is there layering? Are there fossils? Large interlocking grains with no layering mean slow cooling, so it is an intrusive igneous rock. Fine uniform grains mean fast cooling, an extrusive igneous rock. Layering, rounded grains and possible fossils are evidence of material pressed down layer by layer, so it is sedimentary. Minerals in bands, hard and able to split, are the trace of heat and pressure, so it is metamorphic. Write the three clues in a fixed order on the board and use that order for every rock afterwards, so the answer never depends on a feeling.

Students do: for each of three rocks, write one sentence of the form because of this clue, it is this type.

Scene 2: Five steps: change the position, change the name

Draw the cycle as five positions rather than five nouns: magma, igneous rock after cooling, fragments after weathering and erosion, sedimentary rock after transport, burial and compaction, metamorphic rock after heat and pressure, then melting back to magma. For each step, ask what does the work: cooling by heat loss, breakdown by water and temperature change, transport by water and gravity, compaction by the weight of overlying sediment, metamorphism by heat and pressure. Walk limestone through the whole cycle: limestone is sedimentary and contains calcium carbonate, which breaks down on heating. One kilogram of limestone holds nine hundred grams of calcium carbonate and can release 396 grams of carbon dioxide, which links the chemistry to the geology. Then ask the counterexample: can a sedimentary rock turn directly into another sedimentary rock? No, it must be weathered and transported or metamorphosed first, otherwise the name does not change. Stress that the cycle has no starting point; starting from magma is only a convenience.

Students do: draw the five steps and write one process and one visible feature beside each.

Scene 3: Weathering and erosion: break first, then move

These two words are mixed up constantly. Weathering is breakdown in place, so the pieces have not moved. Erosion is removal, so the pieces have moved. One test: if the material is still there but cracked, it is weathering; if it has gone or moved downstream, it is erosion. Two physical examples: daily heating and cooling makes surface layers flake off; water freezing in a crack expands and splits the rock. Two chemical examples: slightly acidic rain dissolves limestone; iron-bearing minerals oxidise to a reddish brown. Use a local case: weathered granite in Hong Kong forms a loose surface layer that fails during heavy rain, which is exactly why slope works matter here. Finally link to resources: building sand and gravel come from sediment, limestone makes cement, metals come from ores, and all of them need the cycle to concentrate them first, so resources are not unlimited.

Students do: label four events as weathering or erosion and write one reason each.

04 Question types and worked steps

Type	Example	Steps	Answer
Identification	Classify a rock from its grain and layering description	Grains, then layers, then fossils, in order	The reason must cite a clue, looks like it does not score
Cycle path	Write the path from magma to sedimentary rock	Five positions with a process at each	Missing transport or compaction loses marks
Explanation	Why do Hong Kong slopes fail after heavy rain?	Loose weathered layer, water uptake, loss of strength, gravity	Separate weathering from erosion in the answer
Resource question	Which rock type supplies cement?	Limestone is sedimentary, heated to give lime	Move from rock type to use

Sanity check (teach this): Sanity check: the whole chapter uses only three clues, so students do not memorise fifteen rock names; the cycle is taught as five positions rather than five nouns, because a position implies its process; weathering and erosion are separated by one test about movement, which is the most common confusion in this topic; the local example is restricted to weathered granite and slope safety because students can see it; and the resources section is deliberately last so the lesson does not turn into an economics talk.

05 Independent practice (3 questions)

Question	Answer	What to watch
Identify	Write one classification reason for each of three rocks	Check that a clue is cited
Cycle	Draw five steps from magma to sedimentary rock with processes	Check that transport and compaction appear
Distinguish	Label four events as weathering or erosion	Check the movement test is used

06 Common mistakes and what to say

Mistake	Student writes	Say this
Weathering called erosion	Saying the wind blew the rock away	Is the rock still there? If it is, that is weathering. If it has gone, that is erosion. Answer the position question first.
Cooling reversed	Saying faster cooling gives larger crystals	How much time do the particles have to line up? Less time means a less ordered pattern and smaller crystals. You have it backwards.
Cycle as a line	Saying rocks only go from magma to sedimentary rock	Where does metamorphic rock go next? Melting returns it to magma. This is a loop, not a line.
Resources as unlimited	Saying rocks are everywhere so it does not matter	It must be pure enough, extractable and transportable. Miss one and it is not a resource. Say it again.

07 Homework (paper, section and question numbers)

Junior Science chapter index — All chapters for this subject
Full prep guide index — Matching chapters in other subjects
Redo this chapter — Practice section, questions 1, 3 and 5: identification, cycle path, weathering versus erosion

08 Exit check (last 5 minutes)

Question	Answer	Decision
Three clues	Grains, layers, fossils	Colour only means returning to scene one
Five steps	Magma, igneous, weathering and transport, sedimentary, metamorphic	A straight line means repeating scene two
Weathering and erosion	Breakdown in place versus material moved	Mixing them means returning to scene three

09 Tutor FAQ

How many rock names must be memorised?

The syllabus asks for two or three examples per group; the clues and the cycle position matter far more than the names.

Should Hong Kong geology be taught?

Five minutes on weathered granite and landslides is worth it, because students can see the evidence themselves.

Is plate tectonics needed?

At junior level it is enough to know that metamorphism and magma involve the earth internal heat; the plate mechanism belongs to senior Geography and Physics.

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A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.