Name ____________________________
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Date ___________________
Class____________
Guided Reading and Study
Properties of Magma
This section explains physical and chemical properties, the property of viscosity, and
the factors that determine the viscosity of magma.
Use Target Reading Skills
As you read about the viscosity of magma, fill in the detail boxes that explain
the main idea in the graphic organizer below.
Main Idea
Magma‘s viscosity depends on . . .
Detail
Detail
Detail
Physical and Chemical Properties
1. A substance that cannot be broken down into other substances is called
a(n) ____________________.
undergoing a physical change. ____________________
3. Circle the statements that indicate a chemical property.
a. Water boils at 100˚C under normal conditions.
b. When paper is burned, it forms ashes.
c. An iron chair will develop rust if oxygen combines with the iron.
d. A basketball is larger than a baseball.
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2. Is the following sentence true or false? When frozen water melts, it is
Name ____________________________
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Date ___________________
Class____________
Guided Reading and Study
Properties of Magma
(continued)
What Is Viscosity?
4. Fill in the blanks: The greater the viscosity, the ____________________ a
liquid flows. The ____________________ the viscosity, the more easily a
liquid flows.
5. Circle the liquids that have a relatively low viscosity.
a. milk
b. molasses
c ketchup
d. orange juice
e. milkshake
Viscosity of Magma
6. What factors determine the viscosity of magma? ____________________________
________________________________________________________________________
7. Circle the letter of each sentence that is true about silica.
a. It is formed from oxygen and nitrogen.
b. It makes magma thicker.
c. It is rarely found in the crust.
d. It produces light-colored lava.
8. The rock ____________________ forms from light-colored lava.
9. Low-silica magma forms rocks like ____________________.
10. What happens to viscosity as temperature increases? ________________________
________________________________________________________________________
11. Hot, fast-moving lava is called ____________________.
12. Cool, slow-moving lava is called ____________________.
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Name ____________________________
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Date ___________________
Class____________
Guided Reading and Study
13. Complete the compare/contrast table to organize the physical and
chemical properties of the different types of magma.
Viscosity of Magma
Temperature
Silica Content
High
b.
c.
a.
higher
d.
e. State the relationship between temperature and silica content in
magmas that have high viscosity and magmas that have low
viscosity.
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
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Name ____________________________
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Date ___________________
Class____________
Section Summary
Properties of Magma
Key Concepts
■ Why is it helpful to know the physical and chemical properties
of a substance?
■
What causes some liquids to flow more easily than others?
■
What factors determine the viscosity of magma?
Like all substances, magma and lava are made up of elements and
compounds. An element is a substance that cannot be broken down into
other substances. A compound is a substance made of two or more elements
that have been chemically combined. Each substance has a particular set of
physical and chemical properties. These properties can be used to identify
a substance or to predict how it will behave.
A physical property is any characteristic of a substance that can be
observed or measured without changing the composition of the substance.
Examples of physical properties include density, hardness, melting point,
boiling point, and whether a substance is magnetic. A chemical property is
any property that produces a change in the composition of matter. Examples
of chemical properties include a substance’s ability to burn and its ability to
combine, or react, with other substances.
The physical property of liquids called viscosity is the resistance of a
liquid to flowing. Because liquids differ in viscosity, some liquids flow
more easily than others. In some liquids, there is a greater degree of friction
among the liquid’s particles. These liquids have higher viscosity.
The viscosity of magma depends upon its silica content and
temperature. The major ingredient in magma is silica, a compound made up
of particles of the elements oxygen and silicon. The amount of silica in
magma helps to determine its viscosity. The more silica magma contains, the
higher its viscosity. Magma that is high in silica produces light-colored lava
that is too sticky to flow very far. The less silica magma contains, the lower its
viscosity. Low-silica magma flows readily and produces dark-colored lava.
Viscosity increases as temperature decreases. The hotter magma is, the
lower its viscosity and the more rapidly it flows. Cooler types of magma
have high viscosity and flow very slowly. Temperature differences produce
two different types of lava. Pahoehoe is fast-moving, hot lava that has low
viscosity. Aa is lava that is cooler and slower-moving. It has higher viscosity
than pahoehoe.
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Name ____________________________
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Date ___________________
Class____________
Review and Reinforce
Properties of Magma
Understanding Main Ideas
Classify each of the following properties by writing Physical or Chemical in the
blank beside it.
______________ 1. Density
______________ 4. Ability to react
with other substances
______________ 2. Boiling Point
______________ 5. Hardness
______________ 3. Ability to burn
______________ 6. Magnetic quality
Answer the following questions.
7. Why is it helpful to know the physical and chemical properties of a
substance? ______________________________________________________________
________________________________________________________________________
8. Explain why molasses has a higher viscosity than water. ______________________
________________________________________________________________________
________________________________________________________________________
9. What is the difference in silica content and viscosity between light-colored
and dark-colored magma? __________________________________________________
________________________________________________________________________
________________________________________________________________________
10. How does temperature affect viscosity of magma?
________________________________________________________________________
Building Vocabulary
Fill in the blank to complete each statement.
11. A substance made of two or more elements that have been chemically
combined is called a(n) ____________________.
12. A(n) ____________________ is a substance that cannot be broken down
into other substances.
13. Fast-moving, hot lava that has low viscosity is called
____________________.
14. Lava that is cooler and slower-moving is called ____________________.
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Date ___________________
Class____________
Enrich
Pegmatites
Can you imagine a mineral crystal as big as a truck? Such crystals do exist.
They sometimes are found in pegmatites, which are a type of mineral
deposit. Pegmatites form from low-viscosity, watery magma. As the magma
cools and starts to harden beneath Earth’s surface, the magma that’s left
becomes more and more watery. All of this water lowers the viscosity of the
magma, which makes it more fluid. In some cases, the last magma to cool
and harden can have a lot of water. In the more fluid magma, atoms are able
move long distances. These atoms combine to form the large crystals found
in pegmatites. Pegmatites often contain gems and rare elements. The rare
elements are concentrated in the watery magma that forms pegmatites. The
table below includes the locations of some important pegmatites in the
United States.
Some Important Pegmatites in the United States
Location
Characteristic
Black Hills, South Dakota
Contains crystals more than 10 m long
Petaca, New Mexico
Contains the mineral uraninite, an ore of uranium
Oxford County, Maine
Deposit is mined to obtain lithium, a rare element
Kings Mountain, North Carolina
Includes gem-quality minerals, such as aquamarine
Answer the following questions on a separate sheet of paper.
1. What effect does water have on the viscosity of magma?
3. According to the table, which pegmatite in the United States contains
uranium ore?
4. Which pegmatite has a lot of aquamarine, a valuable gem?
5. Why are pegmatites important to society?
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2. How do the crystals in pegmatites form?