Week 2 - Lesson 1.2 Elements Flashcards
A pure substance is called an ____. An ____ is a pure substance because it cannot be separated into any other substances. Currently, 92 different ____ are known to exist in nature, although additional elements have been formed in labs.
Elements
Q: Do you know properties of any other elements? For example, what do you know about helium?
A: Helium is a gas that has a lower density than air. That’s why helium balloons have to be weighted down so they
won’t float away.
Q: Living things, like all matter, are made of elements. Do you know which element is most common in living
things?
A: Carbon is the most common element in living things. It has the unique property of being able to combine with
many other elements as well as with itself. This allows carbon to form a huge number of different substances.
For thousands of years, people have wondered about the substances that make up matter. About 2500 years ago,
the Greek philosopher ____ argued that all matter is made up of just four elements, which he identified as earth,
air, water, and fire. He thought that different substances vary in their properties because they contain different
proportions of these four elements.
Aristotle
The smallest particle of an element that still has the properties of that element is the
Atom
Q: Why do you think coal and sugar are so different from one another when carbon is a major component of each
substance?
A: Coal and sugar differ from one another because they contain different proportions of carbon and other elements.
For example, coal is about 85 percent carbon, whereas table sugar is about 42 percent carbon. Both coal and sugar
also contain the elements hydrogen and oxygen but in different proportions. In addition, coal contains the elements
nitrogen and sulfur
This is a pure substance that cannot be separated into any other substances. There are 92 naturally
occurring elements.
Elements
Each element has a unique set of properties that is different from the set of properties of any other element
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For about 2000 years, people accepted Aristotle’s idea that all matter is made up of just four elements: earth,
air, water, and fire. Starting about 500 years ago, scientists began discovering all of the elements that are
known today
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• The smallest particle of an element that still has the properties of that element is the atom. All the atoms of an
element are like one another, and are different from the atoms of all other elements.
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All matter consists of one or more of these elements. Some elements are very common; others are
relatively rare. The most common element in the universe is _____, which is part of Earth’s atmosphere and a
component of water.
hydrogen
The most common element in Earth’s atmosphere is _____, and the most common element
in Earth’s crust is ____
The most common element in Earth’s atmosphere is nitrogen, and the most common element
in Earth’s crust is oxygen.
He had the right idea, but he was wrong about which substances are
elements. Nonetheless, his four elements were accepted until just a few hundred years ago. Then scientists started
discovering many of the elements with which we are familiar today. Eventually they discovered dozens of different
elements.
Aristotle
This actually consist
of smaller particles, including protons and electrons, but these smaller particles are the same for all elements.
Atom
All the atoms of an element are like one another, and are different from the atoms of all other elements. For example,the atoms of each element have a unique number of protons.Consider carbon as an example. Carbon atoms have six protons. They also have six electrons. All carbon atoms are the same whether they are found in a lump of coal or a teaspoon of table sugar (Figure 1.3). On the other hand, carbon atoms are different from the atoms of hydrogen, which are also found in coal and sugar. Each hydrogen atom
has just one proton and one electron.
Atom
