Download Chemistry - Falcon Science

** DO NOT Write on this Sheet! **
Classifying Rocks Using A Key
Introduction:
(Write 5 notes in your own words that will help you answer the questions in this lab)
Rocks are naturally occurring solids that are made of minerals. Rocks can be identified by texture and
composition. Geologists classify rocks into three major groups based on how the rocks form. Igneous rocks
form when lava or magma cools. Extrusive rock forms when lava cools quickly at or near Earth’s surface.
Extrusive rocks have either a fine-grained texture or a glassy texture. Intrusive rocks form as magma cools
slowly farther beneath Earth’s surface, giving the rock a coarse-grained texture.
Sedimentary rocks form when pieces of rock become sediment through weathering and then are compacted and
cemented. Clastic rocks are sedimentary rocks that are made of fragments of weathered Earth materials.
These fragments can be large like pebbles or fine like grains of sand. Chemical rocks are sedimentary rocks
that form when minerals settle out of a solution. Biochemical rocks are sedimentary rocks that form as the
result of a biological process.
Metamorphic rocks form when existing sedimentary rocks are put under intense pressure and heat. They can
either be foliated, meaning the components are arranged in parallel bands, or nonfoliated, meaning the rocks
components are not arranged in bands. Recall that texture is how a rock feels due to its shape, size, and
composition (what it’s made of). Different types of rocks have different textures due to variation in their crystal
size and arrangement (how they are “put together!”)
Purpose: (Rewrite the purpose in your own words)
In this lab, you will use what you have learned about rocks as well as the information on minerals from Chapter
2 to identify some common rocks.
Problem: How can you use composition and texture to identify common rocks?
Pre-Lab: (Answer ALL questions in COMPLETE SENTENCES)
1. In your own words, describe what is meant by a rock’s “texture.”
2. What are two types of Igneous Rocks? What distinguishes these two types of Igneous Rocks?
(How are they different?)
3. What are the three types of Sedimentary rocks? Which type of sedimentary rock would be
formed if we evaporated water that had reactive minerals mixed in it?
4. Chalk is made of tiny fragments of marine animals. To which group of rocks does chalk belong?
5. Suppose you observe a rock with very clear bands (stripes). What type of rock might this be?
What other group might it belong to? Explain.
Materials:
Rock samples
 Hand lens

Dilute HCl
 Paper towels


Classification Tab
***DO NOT WRITE ON THIS LAB***
Procedure:
1. Observe one rock sample. Examine its 1.)texture, 2.)color, 3.)crystal size, and 4.)composition
with and without the hand lens.
2. Use Data Table 1 (“Key to Rock Classification”) to classify the sample. Start by reading the
first question, answer YES or NO based on your observations.
3. After the words “YES” or “NO” you will find directions to proceed to another question, or
you will discover which group your rock belongs to.
4. Copy Data Table 2, and record the “route” you take through the key, using the numbers of
the questions. For example, your route might be “1-4-5-Extrusive Igneous Rock.”
5. Write the name of each rock group in the last column of Table 2 for each sample.
6. Continue working through the table until you have classified all of your rock samples.
7. Compare your classifications with those provided by your teacher, when everyone is done.
Correct any mistakes.
Observations: (Follow the directions after you complete your box)
DATA TABLE 1:
(USE this table, do NOT copy it!!)
Data Table 2:
***DO NOT WRITE ON THIS LAB***
COPY & Fill-out this Table!
Letter of Sample
Route Taken
Group to Which Rock
Belongs
Analysis and Conclusion: (Answer ALL questions in COMPLETE SENTENCES)
1. Using Tables & Graphs: How difficult was it to us the key to classify your rock samples?
What problems did you have? ____________________________________________
__________________________________________________________________
2. Generalizations: How useful was the rock’s color in classifying the samples? Explain your
answer.___________________________________________________
__________________________________________________________________
3. Generalizations: Describe the overall texture of each of the MAJOR GROUPS of rocks.
Copy & Complete the following table…
Rock Type
Igneous
Major Rock Group
Description of Texture
Intrusive
Extrusive
Clastic
Sedimentary
Chemical
Biochemical
Metamorphic
-- -- -- n/a -- -- --
Foliated
Nonfoliated
4. Classifying: Which two of the rock samples were the easiest to classify? What
properties made them easy to classify?_____________________________________
__________________________________________________________________