Science

Common mistakes in rocks and the rock cycle

3 mistakes learners make with rocks and the rock cycle, each one named and explained.

All common mistakes

How a rock formed is what names it, not what it looks like.

A property offered as a rock type

What it looks like

Magnetic or soluble is chosen as one of the three rock types.

Why it happens

It is a real word about rocks, and the three real types are not securely known.

A worked example

Question. The three rock types

A common answer. magnetic

The answer. igneous, sedimentary, metamorphic

Why. Magnetic describes what a rock does, not how it formed.

Put the two side by side

There are exactly three types, all named by formation.
Any other adjective is describing a property.

Learn the three as a closed list. Anything outside it is not an option.

A rock type matched to the wrong formation

What it looks like

Igneous or metamorphic is given for rock formed from layers of sediment.

Why it happens

Three names, three processes, and nothing about the names says which is which.

A worked example

Question. Rock formed from layers of sediment squashed over time

A common answer. igneous

The answer. sedimentary

Why. Sedimentary is named directly after sediment.

Put the two side by side

Igneous: cooled from molten rock, and ignis means fire.
Sedimentary: settled sediment. Metamorphic: changed by heat and pressure.

Each name describes its own process once you hear the root inside it.

The rock cycle run backwards

What it looks like

Sedimentary rock is said to form before the sediment it is made of.

Why it happens

Rock is the more substantial thing, so it feels like the starting point.

A worked example

Question. Which forms first, sediment or sedimentary rock

A common answer. sedimentary rock

The answer. sediment, which is then compacted and cemented into rock

Why. You cannot compact something that does not exist yet.

Put the two side by side

Weathering makes sediment.
Burial and pressure turn sediment into rock.

Every step of the rock cycle has an input. Name the input and the order fixes itself.

WAJD spots these patterns in your child's answers and names the one behind their wrong answers, instead of just marking them wrong.

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