Basic Concepts (All About Matter)

Chemistry is the study of matter and energy and the interaction between them ¹. What is matter? the word "matter" is used to cover all substances and materials from which the physical universe is composed ². So basically matter is anything that has mass and occupies space. Any material object, no matter how large and small, is composed of matter. Matter can exist as a solid, a liquid or a gas. These three forms of matter are called the state of matter. But then if I raise a question regarding this concept such as " are light, heat and sound included as matter?". The answer is NO. They are forms of Energy. Energy is the ability to produce change ¹. So we can conclude that whenever the matter changes from one state to another, energy is involved.

Every substance has certain characteristics that distinguish it from other substance. Those characteristics that serve to distinguish and identify a specimen of matter are called the properties of a substance. Physical properties are the properties related to the appearance of the substance. The example of these physical properties are density, color, melting point, boiling point, freezing point, hardness and state at room temperature. Chemical properties are the properties related to the chemical reaction (how it reacts). The example of these chemical properties are flammability, rust resistance, reactivity, etc ¹.

The theory used to explain the states of matter is the kinetic theory of particles. In order to use this theory properly you should imagine that all substances are made up of tiny particles.  To help you to do it, let me give you a simple picture of it.

The main points of this theory are:

1. All matter is made up of tiny particles, that cannot be seen through naked eye. Different substances have different size of particles
2. The particles move all the time. The higher the energy, the faster they move on average
3. The heavier the particles, the slower they move on average ².

By using this theory we can explain the states of matter (its behaviors and properties). The summary can be seen in a table below.

	Solid	Liquid	Gas
Arrangement of Particles	They are close together	They are close together	They are far apart
	They are in a regular pattern called a crystal lattice*	They are in a random pattern	They are in a random pattern
	Strong attractive forces	Strong attractive forces (aren't as strong as they are in a solid)	Weak attractive forces
Movement of Particles	They vibrate in their fix position	They move around each other	They move quickly in all directions
Properties	A Solid has a definite shape and volume	A Liquid has a fixed volume and take up space of its container	It takes up space of its container
	Slightly increase in size when heated	Expand when heated and contract when cooled.**	The volume of gas are affected quite markedly by changes in temperature.
	Slightly decrease in size when cooled	They can't be compressed***	They can flow
	They cannot be compressed or squashed	They can flow
	They cannot flow

*      Organized structure of repeating patterns ³.

**    Water will contract when heated from zero degree to four degree Celsius but expands above four degree Celsius. It will expand when frozen due to the strange shape of water (the presence of hydrogen bonds)⁴.

 ***  For advance physical chemistry liquid still can be compressed. Its compressibility constant (k) is very small. The liquid has a very low compressibility simply because there is very little empty space⁵.

Reference:

1 Goldberg, D E., 2005, Beginning Chemistry 3rd Edition, United States of America, McGraw-Hill Companies, Inc. p.1.

2 Earl, B and Wilford, L D R., IGCSE Chemistry, Dubai, Hodder Murray. p.1.
3 Moore, J T., 2010, Chemistry Essentials for Dummies, Canada, Wiley Publishing, Inc. p.7.
4 Why does water expand when it freezes?, (2009, October 11), Retrieved from http://www.thenakedscientists.com/HTML/questions/question/2435/
5 Castellan, G W., 1983, Physical Chemistry 3rd Edition, United States of America, Addison-Wesley Publishing Company, Inc. p. 87.