Download How can you tell rocks apart?

How can you tell rocks apart?
Grade Range: 4 - 7
Time Budget: 1 – 1.5 hours
G.L.E Focus: 1.1.5
WASL Vocabulary:
Overview: Different rocks have different characteristics because of their minerals, the
ways in which the rocks were formed, and the processes that acted on the rocks since
they were formed. In this activity, students will explore how to use the physical
characteristics of rocks to group and identify rocks. They will then use their observations
of the rocks to identify a particular rock from a collection.
Learning Objectives:
• Collect and organize data about rocks
• Distinguish rocks from each other using physical characteristics and then be able
to identify rocks out of a particular collection
• Gain knowledge about what a rock is composed of and how different types of
rocks are formed
Sources: American Geological Institute (AGI)
(c) 2004, 2008 Andrew Alden, geology.about.com, reproduced under educational fair use
Materials
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Rock collection (2 sedimentary, metamorphic and igneous rocks; rocks have stick on
numbers 1-6 on them)
6-9 Magnifying lenses/ or hand lenses
Rock Data Table (below)
Rock Identification Sheet (below)
Colored pencils/ or crayons
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Flipchart or large pieces of paper to record the student’s observations on
Markers
Preparation
1. Photocopy Rock Data Table and Rock Identification handouts.
2. Assemble a set of various types of rocks to use while leading the initial discussion
about rocks in the introduction activity.
Lesson Plan
Introduction Activity: What do your students already know about rocks?
Preparation: You will need the collection of rocks you have gathered, large pieces of
paper and writing markers for recording the student’s answers.
Picking up, examining and collecting rocks can be the first steps in moving children
toward an appreciation of geology and the “bones” of the Earth. Even very young
children enjoy picking up rocks, lining them up, choosing “favorite” ones, pouring water
over them to make them shiny. By letting children handle and observe rocks you give
them an entry point to learning about their planet and the processes that shape the planet.
Most children have seen and touched rocks, even if they have only picked up gravel from
a driveway. They typically describe rocks as “hard” and “heavy.” They will know that
rocks are different colors, shapes and sizes, but they may know little about the types of
rocks and how these are formed.
1. Assemble the class in front of the group of rocks you have gathered. Pass the rocks
around or divide them among the groups if you prefer breaking into smaller groups.
2. Discuss the questions below as a class or in smaller groups, and then have the groups
share their answers with the class.
• What is a rock?
• What kinds of rocks are there?
• Where do rocks come from?
• How can you tell different kinds of rocks apart?
• How do humans use rocks?
3. As the students are sharing their ideas, record their answers on the large pieces of
paper.
4. You can extend this activity further by asking the students “ What they would like to
learn about rocks?” Record their questions. From this question you can help students
realize that scientists try to find out about the world by asking questions, predicting
likely answers and conducting tests to see if their ideas are correct or not.
Activity 1: How can you tell rocks apart?
1. After concluding the introduction activity where you assess what the students already
know about rocks, introduce them to the investigation question “How can you tell
rocks apart?” They will be working on this question for the remaining time and will
find out concrete answers. Additional questions you can ask to get students to think
more deeply about the main investigation question are:
• What characteristics can you observe in rock samples?
• Different types of rocks form in different ways. How do the differences in the
rock formation processes influence the way a rock looks?
• How do the characteristics of rocks indicate how the rocks were formed?
2. Divide your class into groups of about four students with each group sitting around its
table or work area.
3. Before your students begin, tell them how much time they will have to complete their
investigation. (Group learning strategies often call for appointing a group time-keeper
who keeps the group on track.)
4. Provide your students with the following tools for investigation:
• Hand lenses (1-2 per group)
• Rock sample set (contains rocks #1-6, which are sedimentary, metamorphic
and igneous samples)
• Rock Data Table (below)
• Colored pencils to share
5. Tell your students that their job is to really study their rocks using their senses and
their hand lenses to make observations. They need to write down and draw their rock
observations on the Rock Table handout provided.
6. After the have examined the rocks for several minutes. Ask the students which
characteristics are they using to describe their rock samples. Make a list on the board
for all students to view. If these characteristics are not mentioned, consider
describing them and adding them onto the list. (color, texture, size of grains or
crystals, layering of crystals, different types of minerals present, angularity of the
grains)
7. When they finish, ask students to use the data in their tables to make three groups of
rocks. The rocks in each group should have similar characteristics. When they have
done this, ask groups to volunteer to share their groupings and their reasons for them.
8. Give students copies of the Rock Identification Sheet. Ask them to use the sheets and
their Rock Data Tables to identify the groups in which their rocks belong. If they feel
confident about this, they can try to identify the specific names of the rock samples.
Make sure to emphasize that a certain rock type may look slightly different than the
pictured samples. (For example, types of granite come in many shapes and
compositions. They can range from salt and pepper in appearance to having pink
minerals also. Also the crystals can be small (2-5 mm) or very large (1-2 cm))
9. When students are finished, hold a whole class discussion about how it is possible to
use the characteristics of rocks to group them. Make a list of their ideas on a large
piece of paper for later. Please discuss what are the three main types of rocks
(sedimentary, metamorphic, igneous) and how each rock type is created (see
background information).
Activity 1 Extension A: Go over the questions students had about rocks before this
activity. As a class, try to answer them. If they cannot be answered, discuss what
information you would need to answer the question. How would you go about getting
that information or answering your question?
Student Assessment
Complete this investigation by asking your students to reflect on the “how can you tell
rocks apart?” question and how their answers may have changed as a result of this
investigation. For example, most rocks are pretty hard and are solid, but they are different
in color, texture, size, shape and shininess. Also, ask students what they now know about
rocks that they didn’t know before. Ask them what questions they now have about rocks
that they hadn’t thought of before the investigation. Write these down for later.
Assessment 1: Give each group a new set of rocks (you can switch rocks from group to
group) and ask the students to group the rocks based upon their characteristics. Ask them
to give a reason for why they placed each rock in its group.
Activity Background Information
There are three main categories of rocks, which are defined by how the rocks are formed.
Sedimentary Rocks
Sedimentary rocks are formed from sediment, which is solid, loose pieces of rocks (in the
form of sand, silt, clay, and gravel), or the remains of living things found at the surface of
the Earth. Sediment is material that has been eroded and deposited by wind, running
water, waves, and ice. Sediment can also form from material left behind by the
evaporation of seawater, or the settling of the remains of animals and plants in oceans,
lakes, and swamps. In certain conditions, and over a very long period of time, sediment
can become compacted and cemented into sedimentary rock. Sedimentary rock is often
found in layers. One way to tell if a rock sample is sedimentary is to see if it is made
from grains.
Igneous Rocks
Rocks are mixtures of one or more minerals. Just like the apples, butter, flour, and sugar
are the ingredients of apple pie, minerals like quartz, mica, and feldspar are the
ingredients of an igneous (from the Latin word for fire) rock called granite. Igneous rocks
come from melted rock material, or magma, that lies under Earth’s surface. Igneous rocks
form when magma from inside the Earth moves toward the surface, or is forced above the
Earth’s surface as lava and ash by a volcano. Here it cools and crystallizes into rock.
Metamorphic Rocks
Metamorphic rocks are rocks that have become changed by intense heat or pressure while
forming. In the very hot and pressured conditions deep inside the Earth’s crust, both
sedimentary and igneous rocks can be changed into metamorphic rock. In certain
conditions these rocks cool and crystallize, usually into bands of crystals. Later they can
become exposed on Earth’s surface. One way to tell if a rock sample is metamorphic is to
see if the crystals within it are arranged in bands.
Web Resources
http://www.k5geosource.org/activities/invest/rock/q2/pg1.html
http://geology.about.com/library/bl/images/blrockindex.htm
Activity Handouts
Note: The Rock Identification handout is a separate pdf file.
Activity 1: ROCK DATA TABLE
Name:________________________________________________________
Sample
Number
Observations
Type of Rock (sedimentary,
metamorphic, igneous)