Download Purpose - Net Start Class

Science 8
Laboratory Activity
Under Pressure
EQ: Why are constructive forces so
destructive?
Targeted Skills
 Information Literacy
 Evaluate information
 draw conclusions, make inferences, and connections
based on information
 Thinking and Reasoning
 Creative thinking
 patterns
 classify
Purpose
Enduring Understanding
Earth is a dynamic system.
Changes result from the interaction between matter and
energy.
Concepts Important to Know and Understand
properties of matter, changes in Earth systems,
internal/external forces, physical and chemical actions
Broad Brush Knowledge
rock cycle, formation of rocks, chemical formulas, periodic
table
Core Objectives
15. Identify chemical and physical properties used to classify
matter and determine everyday applications.
16. Demonstrate that substances may react chemically to
form new substances, which can be represented in a
chemical equation.
Compare and analyze the composition of metamorphic rocks to the parent sedimentary,
igneous, or earlier metamorphic rock formations.
Expert Information: Metamorphic rocks started out as other types of rock, but have been
substantially changed from their original igneous, sedimentary, or earlier metamorphic form.
Metamorphic rocks form when rocks are subjected to hot, mineral-rich fluids, high heat, high
pressure, or more commonly, some combination of these factors. Conditions like these are
found deep within the earth or where tectonic plates meet. Stresses caused by tectonic plates
colliding during the process of mountain building or during times when plates slide past each
other, change rocks.
All rocks are composed of minerals.
These minerals have definite chemical
arrangements and are normally stable only under certain conditions. When conditions change in
the surrounding areas, the crystal arrangement of the minerals will change. Heat and pressure
applied to rocks during the metamorphic process cause the minerals composing them to bend,
break, stretch, or reform. Exposure to heat and pressure can reshuffle existing elements to
change mineral composition. This process can occur without rocks actually melting, but can
cause recrystallization of the minerals that are present. The word metamorphic literally means
(meta-) change and (morph) form. This definition very accurately describes this type of rock
formation. In metamorphic rocks, some or all of the minerals in the original rock are replaced,
atom by atom, forming new minerals.
Identifying chemical properties of a rock or mineral is difficult and can be a very
involved process.
Scientists can more easily identify physical characteristics.
When
identifying metamorphic rocks, the first characteristic used to aid in identification is banding.
If bands or layers form during the metamorphic process, the rocks are classified as foliated.
If bands or layers do not occur, the rocks are classified as nonfoliated. These two
characteristics are the basis for dividing metamorphic rocks into two subgroups.
© 2006 Plano ISD, Plano, TX
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Materials
One sample each
Gneiss
Quartzite
Marbel
1M HCl acid
dropper bottles
safety goggles
Procedure
Part 1
1. Observe all three samples of rocks. Carefully describe the characteristics of each sample.
In our chart below.
2. Test each rock with one or two drops of hydrochloric acid.
3. Record results.
Data Analysis
1. Fill in the chart below identifying the igneous or sedimentary rock each metamorphic rock
originated from and explain the reasoning for the choices.
Metamorphic Rock Origins
Metamorphic
Rock
Gneiss
(Pg. 403)
Parent Igneous or
Sedimentary Rock
Reasons to validate choice
Quartzite
Marblel
2. Which parent rocks were the easiest to identify?
Explain.
3. Explain how two samples of the same metamorphic rock might not look identical.
4. List some difficulties you could encounter when trying to identify certain rock types.
5. Which physical or chemical properties are most useful in classifying rocks? Explain your
answers.
6. Both gneiss and marble are used for building materials such as cabinet tops. Explain why
gneiss would be a better choice than marble for kitchen cabinet tops where they would be
exposed to vinegar, lemon juice, and other acids.
© 2006 Plano ISD, Plano, TX
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