Rocks and Minerals — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
Sedimentary rocks form when melted rock cools and hardens underground or on the surface.
Corrected: Igneous rocks form when melted rock cools and hardens. Sedimentary rocks form when layers of sediment are pressed and cemented together.
The corrected sentence is: "Igneous rocks form when melted rock cools and hardens. Sedimentary rocks form when layers of sediment are pressed and cemented together.". The original sentence "Sedimentary rocks form when melted rock cools and hardens underground or on the surface." contained an error that needed to be fixed.
2. Fix the sentence:
Metamorphic rocks are formed by layers of sand and mud piling up at the bottom of a lake.
Corrected: Metamorphic rocks are formed when existing rocks are changed by extreme heat and pressure deep inside the Earth.
The corrected sentence is: "Metamorphic rocks are formed when existing rocks are changed by extreme heat and pressure deep inside the Earth.". The original sentence "Metamorphic rocks are formed by layers of sand and mud piling up at the bottom of a lake." contained an error that needed to be fixed.
3. Fix the sentence:
Granite is a sedimentary rock made from layers of compressed sand.
Corrected: Granite is an igneous rock that forms when magma cools slowly underground, allowing large mineral crystals to grow.
The corrected sentence is: "Granite is an igneous rock that forms when magma cools slowly underground, allowing large mineral crystals to grow.". The original sentence "Granite is a sedimentary rock made from layers of compressed sand." contained an error that needed to be fixed.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. Rocks that form from cooled magma or lava are called igneous rocks.
Igneous rocks form when magma (underground) or lava (surface) cools and solidifies. Examples: granite, basalt, obsidian.
2. Rocks made from layers of sediment pressed together are called sedimentary rocks.
Sedimentary rocks form when sediment (sand, silt, shells) accumulates in layers and is compacted over time. Examples: sandstone, limestone, shale.
3. Rocks changed by heat and pressure are called metamorphic rocks.
Metamorphic rocks form when existing rocks are transformed by intense heat and pressure deep in Earth. Examples: marble, slate, quartzite.
4. The continuous process of rocks changing from one type to another is the rock cycle.
The rock cycle describes how rocks continuously change between igneous, sedimentary, and metamorphic forms over time.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. How does an igneous rock form? Give one example.
Sample answer: Igneous rocks form when hot melted rock called magma or lava cools and hardens. Granite is an example that forms when magma cools slowly underground.
Key concepts: magma/lava + cooling + hardening = igneous rock. Intrusive (slow, large crystals): granite; extrusive (fast, small crystals): basalt.
2. What is the difference between a rock and a mineral?
Sample answer: A mineral is a single natural substance with a specific chemical makeup, like quartz. A rock is made of two or more minerals combined together, like granite which contains quartz, feldspar, and mica.
Minerals are pure crystalline substances; rocks are aggregates of one or more minerals.