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Date: __________
Elements, Compounds, and Mixtures
Science Literacy Article
You are surrounded by elements, compounds, and mixtures everywhere you go.
These substances can be solids, liquids, or gases.
Elements are pure substances that are not able to be broken down chemically.
There are well over 100 elements that exist on Earth. All of the elements that
have been discovered are listed on the Periodic Table of Elements. Examples
of elements include solids such as iron (Fe), liquids such as mercury (Hg), and
gases such as oxygen (O).
Compounds are pure substances that are composed of two or more different
elements that are chemically combined (bonded). Compounds are able to be
broken down chemically and contain different properties than the elements that
make them up. Examples of compounds include solids such as salt (NaCl),
liquids such as water (H2O), and gases such as carbon dioxide (CO2).
Organic compounds contain the element carbon and at least one atom of
hydrogen, oxygen, phosphorus, sulfur, or nitrogen. Carbon is the central
element to all living organisms. Organic compounds that are vital to living
organisms include carbohydrates, lipids, proteins, and nucleic acids.
Mixtures are composed of two or more different elements or compounds that
are not chemically combined. The substances in a mixture do not change
chemically and keep their properties. These substances are able to be separated
by different processes (i.e. filtration, evaporation, etc.). Examples of mixtures
include solids such as sand, liquids such as milk, and gases such as air. There
are two main types of mixtures:
1.Homogeneous mixtures have a uniform (constant) composition and the
same properties throughout (i.e. a cup of coffee).
2.Heterogeneous mixtures are not uniform in their composition and are
made of different substances that remain physically separate (i.e. trail
mix).
To recap, here is the important vocabulary:
• Elements are pure substances that cannot be broken down.
• Compounds are pure substances that can be broken down into elements
through chemical reactions.
• Organic compounds contain carbon and one or more of these:
hydrogen, oxygen, phosphorus, sulfur, or nitrogen.
• Mixtures are not chemically combined and can be taken apart without a
chemical reaction.
• Homogeneous mixtures look the same throughout and have the
same properties.
• Heterogeneous mixtures have parts with different properties.
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