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Substances

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Substances, Elements, and Compounds
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Substances

License: CC BY-NC 3.0

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Substance is matter that has a uniform and definite composition.

Substances exist as either elements or compounds, and can exist in solid, liquid, or gas forms.

Beware! Homogenous mixtures are NOT substances. You can identify what is a substance and what isn't based on whether or not it is separable by physical means. Substances cannot be physically separated.

Why is it important to use chemical substances in experimentation? 

Look around you. Substances are everywhere. Name some examples that you notice.

Elements

Aristotle believed that there existed four elements: earth, water, wind, and fire; however, we know today that that is not the case. Scientists today have identified myriad elements which have been compiled into a table we call the periodic table.

Elements are pure substances, or matter that cannot be chemically broken down into simpler forms.

Elements are made up of particles called atoms. Atoms of elements may combine to form new substances.

Not all substances exist in their pure elemental forms. What are some substances that do?

There are three types of particles that make up atoms. What are these called and what are their respective properties? Answer these questions by filling out the table below.

Name of particle Charge Size

Which subatomic particle determines the identity of an element?


Compounds

While there are a lot of elements, most of the matter that we interact with on a daily basis are not pure elements but actually compounds, or substances formed by two or more elements which are combined in a fixed ratio.

Note: The identity of a compound can be changed only through chemical changes, and not physical ones.

There are many different types of compounds. Research some common properties of ionic and molecular compounds.

For guidance in answering the questions in this guide, look here.


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  1. [1]^ License: CC BY-NC 3.0

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