Chemistry – Matter and the Divisions of Matter
Matter is all the stuff around you. It is the food you eat, the air you breathe and the clothes you wear. Even you are made-up of matter. Therefore, you need to know the different types, forms and properties of matter.
Matter is anything that has mass and volume. Mass is the amount of inertia in matter and the volume is the amount of space occupied by matter. Inertia is the resistance to change and the greater the inertia the greater the mass.
DIVISIONS OF MATTER
Many times matter is divided into two categories: pure substances and mixtures. It is important that you can distinguish one form of matter from another so that you can describe the changes you observe.
Pure substances consist of one material with a definite composition and definite properties. Pure substances are divided into two groups: elements and compounds.
Elements are the simplest forms of chemical substances and cannot be broken down by ordinary chemical means. Examples would be hydrogen (H), sulfur (S) or gold (Au). The simplest form of an element is an atom.
Compounds are chemical combinations of elements that can be described with a chemical formula and can only be separated by chemical means. Examples of compounds are water, sugar and salt. The simplest forms of a compound are molecules or formula units.
Mixtures are all around you. A salad is a mixture of vegetables, a glass of soda is a mixture of water, sugar and flavoring and air is a mixture of gases like nitrogen, oxygen and carbon dioxide.
Mixtures are physical combinations of two or more substances with varying compositions, varying properties and can be separated by ordinary physical processes. Usually, mixtures are divided into two main groups: those that are homogeneous and those that are heterogeneous.
Homogenous mixtures are the same throughout and do not separate into phases when left alone. Many homogeneous mixtures are solutions that consist of a solute and a solvent. The solute is the material that dissolves and the solvent is the material that causes the dissolving. Solutions are completely dissolved and see through.
An alloy is a solution of two or more elements, at least one of which is a metal, where the resulting material has metallic properties. Alloys are usually made to improve on the properties of the elements that make them up. Steel for example, is much stronger than iron, which is its main component.
Heterogeneous mixtures have no definite composition and separate into phases when left alone. Heterogeneous mixtures can be separated by ordinary physical means. Examples of heterogeneous mixtures are blood, Italian salad dressing and soda pop.
Another type of mixture is a colloid. A colloid is a suspension that doesn’t separate because the particles aren’t completely dissolved and remain suspended causing the mixture to appear cloudy. This cloudiness, called the Tyndall effect, is due to the scattering of light by the suspended particles.
A solution does not scatter light because the particles are at the molecular level and way too small to reflect light. However, the colloidal particles are large enough to reflect light and yet small enough not to settle. The scattering of light from automobile head-lights in fog and of a light beam by dust particles are examples of the Tyndall effect.
Colloids are formed from all combinations of solids, liquids or gases (except mixtures of non-reacting gases which are true solutions). Aerosols, foams, emulsions and sols are different types of colloids. Examples of colloids are shaving cream, whipped cream and gelatin.