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Molecules

By Dr. Israr Ul Hassan

Chemistry involves the study of the properties and behavior of matter. Matter is the physical material of the universe. It is anything that has mass and occupies space, e.g. the clothes you are wearing, the air that you are breathing, etc. Can you think of any other examples of matter? Write your answer in the box below.

As you begin to understand the fundamentals of chemistry, you will see that the properties of matter relate not only to the kind of atom present but also to the arrangement of atoms.

As you think about the answer, you will become fully aware that there are many examples. All these examples of matter have something in common. This is the fact that all matter contains elementary substances called elements. There are two definitions for an element.

Definition 1

 

Definition 2

An element is a substance which contains

only one type of atom.

 

An element is a substance which cannot be broken

down into anything simpler by chemical means.

Chemistry also provides a background to understand the properties of matter in terms of the small building blocks known as atoms. Each element is composed of only one kind of atom. As you begin to understand the fundamentals of chemistry, you will see that the properties of matter relate not only to the kind of atom present but also to the arrangement of atoms.

Atoms combine to form molecules in which two or more elements chemically combine together. Each molecule has a specific geometric shape. Some examples of molecules are shown below.

Figure 1. Molecule of methane.

 

Figure 2. Molecule of ethane.

The colors represent different atoms. Green represents carbon, and white represents hydrogen.

Different combinations of atoms have a profound effect on the properties of molecules. Even minor changes to the structure of a molecule ion have an effect on the properties of the molecule. For example, if you compare ethanol and ethylene glycol, there is not much of a difference, but the properties are completely different. Ethanol is a type of alcohol used in beer, and ethylene glycol is a viscous liquid used in cars as antifreeze. It stops the water in the engine from freezing at cold temperatures.

In case you are wondering what the term properties means, it is the characteristic either in appearance (physical property) or the types of atoms the molecule contains (chemical properties) which gives the molecule in question a unique type of behavior. Can you think examples of two physical and chemical properties of matter?

So why do we study chemistry?

Once you have answered the questions, e-mail this page to your teacher.

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