Unit 1: Nature of Chemistry

Content Outline: Classification of Matter (1.6)

  1. Classification of Matter
  1. There are two main categories of matter: pure substances and mixtures
  1. Pure substance – this term refers to substances that have uniform composition throughout all samples and uniform properties.
  1. Pure substance can either be elements, such as everything contained on the Periodic Table, or compounds, such as water.
  1. The Periodic table shows the three categories of known elements on Earth: metals, metalloids (like-metals), and Non-metals.
  2. The horizontal rows on the table are called periods.
  3. The vertical rows on the table are called groups or families. This term is used because the elements in a family all have similar properties.
  4. Metals – have the ability to conduct electricity.
  5. Metalloids – possesses some characteristics of metals but also non-metals. (“oid” means “like”… It is like a metal.)
  6. Non-metals – these are poor conductors of electricity. Most are gases.
  1. Mixtures – this term is used for samples of matter that do NOT possess uniform composition throughout all samples with a combination of properties.
  1. Mixtures can even be classified into two groups: homogeneous and heterogeneous.
  1. Homogeneous mixtures – these are mixtures that appear as uniform in composition. (“ homo” means “same”) For example, Kool-aid.

α. Homogeneous liquid mixtures can also be called solutions.

b. Colloid – these are substances that appear uniform, but if left undisturbed will separate based upon density. For example, milk.

ii. Heterogeneous mixtures these are mixtures thatappearun-uniform in

composition. (“hetero” means “different”) For example, a plate of salt and

pepper mixed or a chunk of granite.

  1. Pure substance compounds can only be decomposed by chemical means.

For example, providing electricity to water to convert it to Hydrogen gas and Oxygen gas. This process is called electrolysis.

  1. Mixtures can be separated based upon the unique properties of the composing substances.
  1. Some various ways of separating mixtures include:
  1. Filtration – pouring the sample through filter paper.
  2. Chromatography – separating solutions by differing densities.
  3. Centrifuge – separating particles, in a liquid, by differing densities.
  4. Vaporization – heating off the liquid of solution