Matter is anything that occupies space and has weight. If you look around you, you will see matter. The table, books, walls, and your body are all composed of matter. Obviously, the matter around you is not all the same.
Physical States of Matter. In general, we can group all matter into three groups called states of matter.
- Solids. Solids have a definite shape and volume. Examples of solids are books, rocks, pieces of steel, and sand.
- Liquids. Liquids have a definite volume but indefinite shape. That is, they take the shape of their container. Water, mercury, alcohol, and oils are liquids.
- Gases. Gases have neither a definite shape nor a definite volume. They assume not only the shape of their container, but also the volume of their container. Gases may be expanded or compressed to fit the container in which they are being placed. Therefore, the air in an automobile tire would, if released, expand to fill a large weather balloon.
Properties of Matter. Matter possesses two types of properties, physical and chemical. Characteristics such as smell, color, shape, freezing point, boiling point, and solubility are said to be physical properties of matter. Energy content, reactions with other substances, and chemical reactions due to light, heat, and electricity are said to be chemical properties of matter. From the physical and chemical properties exhibited by a substance, it is possible to isolate, identify, and classify the particular substance.
Classification of Pure Matter. Matter that cannot be separated into two or more types of matter by physical means is called pure matter. Pure matter consists of two types, elements and compounds.
- Elements. Elements are substances that cannot be separated into two or more types of matter by physical or chemical methods. Another way to say this is that elements consist of only one type of atom. An atom is a chemical building block and can be defined as the smallest part of an element that remains unchanged during any chemical reaction and exhibits or displays the chemical properties of that element. Examples of common elements are oxygen, gold, iron, mercury, hydrogen, and carbon. Table 1-1 lists the elements with their symbols, atomic numbers, and atomic weights.
- Compounds. Compounds are composed of two or more elements chemically combined. Compounds are substances that have been purified by physical means, but not by chemical methods. They can be separated into two or more types of matter by chemical methods because their basic unit, the molecule, is a combination of two or more types of atoms. A molecule is composed of two or more atoms and is the smallest part of a compound that can exist and still retain the chemical properties of that compound. Illustrated in this diagram are the relationships of these building blocks and classifications of matter.
Table 1-1. Elements, symbols, atomic numbers, and atomic Weights
in alphabetical order.
Classification of Mixed Matter. Matter that can be separated by physical means is called mixed matter and may be homogeneous or heterogeneous.
- Homogeneous mixtures. Mixtures that are uniform throughout are called homogeneous. An example of a homogeneous mixture is a solution of sugar in water. Any small part of this solution would exhibit the same properties as any other small part; therefore, it would be uniform throughout the mixture.
- Heterogeneous mixtures. Mixtures that are not uniform are called heterogeneous. An example of a heterogeneous mixture is a mixture of water and oil. If a small sample is taken, it may not be the same as another small sample taken from elsewhere in the mixture. This is because oil and water do not mix well--they give a nonuniform mixture.
There are many things in our surroundings that we know exist, yet are not matter. They are forms of energy. Heat, light, and electricity are examples of energy. Energy may be simply defined as the ability to do work or overcome resistance.