Download Reading: Elements that Make Up Our Planet

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Reading: Elements that Make Up Our Planet
Read the text below and answer the questions that follow.
Imagine you are walking along a beach near the ocean. That scene represents
four major components that make up our planet. The sand beneath your feet
is part of the solid Earth. The waves on the shore are a part of the ocean. The
cooling breeze is part of the air. And you are part of the fourth component:
living things. All of these components are very different. Yet they are built from
the same basic elements.
The Solid Earth
The solid part of Earth is a part of the lithosphere. It consists of two layers.
The top layer is the crust, consisting of rock that forms Earth’s surface. Below
the crust is the rigid, upper part of the mantle. The rocks of the lithosphere,
like all rocks, are made of minerals. The most common group of minerals is the
silicates. These minerals contain oxygen and silicon—the two most common
elements in Earth’s lithosphere—joined together. Of the 92 naturally occurring
elements, only five of them—oxygen, silicon, aluminum, iron, and calcium—
make up more than 90 percent of the rocks in Earth’s lithosphere.
Atmosphere
Oceans
Water, of course, is made of hydrogen and oxygen, H2O. But ocean water is
a lot more than that. Ocean water is saltwater. It contains dissolved salts, most
of which contain the elements sodium and chlorine. On average, every kilogram
(1000 grams) of ocean water contains 35 grams of salt. Besides salts, the ocean
contains other dissolved solids, as well as dissolved molecules of the same gases
found in the atmosphere. In fact, the ocean contains all 92 elements that occur in
nature, although most are in very tiny amounts.
Living Things
Living things, whether a bee, a whale, or you, are very similar in the elements
they contain. Almost all of the weight of most living things consists of six
elements—oxygen, carbon, nitrogen, hydrogen, phosphorus, and calcium. The
exact chemical composition can vary. The human body, for example, is about 61
percent oxygen and 23 percent carbon dioxide.
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© Houghton Mifflin Harcourt Publishing Company
Oxygen is a major component of Earth’s atmosphere, too. Oxygen gas
makes up about 21 percent of the atmosphere. That’s a large percentage, but a
whopping 78 percent of the atmosphere is nitrogen. The remaining 1 percent
consists of argon, carbon dioxide, and other gases. The atmosphere’s gases
provide materials essential for living things. Nitrogen promotes plant growth and
is an important ingredient in the chemicals that make up living things. Oxygen
is necessary for animals and plants to perform life processes. Plants use carbon
dioxide along with water to make food.
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Answer the following questions in the spaces provided.
1.What are the two most common elements in the lithosphere?
2.What element is part of the solid Earth, the atmosphere, the oceans, and
living things?
© Houghton Mifflin Harcourt Publishing Company
3.What does ocean water contain besides water?
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