Pure Substances & Mixtures

• Pure Substance

  • kind of matter with definite or fixed composition
  • regardless of the amount of pure substance, it will always have the same properties because it is made up of one type of particle
• Pure Substance Classification:

  1. Elements - simplest substances (made up of only one kind of atom) - can't be decomposed into simpler substances - building blocks of matter - has a place in an arrangement called periodic table of elements
  2. Compounds - made up of different elements - atoms of the elements are joined together by chemical bonds (strong attractive forces)
• Periodic Table of Elements


  A list of all known elements in a tabulated form - arranged with similar properties are close together - columns (groups) & rows (periods)
• Main Groups

  • Metals
  • Nonmetals
  • Metalloids
• Metals

  • Solid at room temperature except mercury (quicsilver)
  • Tensile strength
  • Iron + carbon = steel (alloy)
  • Lustrous (shiny)
  • Ductile (drawn into wires)
  • Malleable (hammered into thin sheets)
  • Good conductors, high melting point & high boiling point
• Nonmetals

  • Either solid or gas at room temp except bromine
  • Brittle, dull, no luster
  • Poor conductors, low melting point, high boiling point
• Metalloids

  • Exhibit properties of both metals & nonmetals
  • Conduct electricity but not as good as metals
  • Semiconductor (material that conduct electricity better than insulator)
  • Some metalloids are shiny like metal but brittle like nonmetal
• Chemical Reactions: (the processes that create compounds, results in (product/new substance) from the elements or compounds (reactants)

  1. Exothermic Reaction - gives off heat when they react - any combustion reaction - iron oxide (rust) - heat content of reactants is greater than the product
  2. Endothermic Reaction - absorbs heat, allowing it to produce new substance - photosynthesis

  (*electrolysis - electric current to water - hydrogen & oxygen - reversible chemical reactions)
• Categorization of Compounds:

  1. Organic Compounds - one or more carbon atoms bounded to other elements (hydrogen,oxygen,nitrogen) -all living things are carbon-hydrogen
  2. Inorganic Compounds - lack carbon-hydrogen bonds - comprises most of earth's crust e.g. carbon monoxide, carbon dioxide, water, salts
• Main Types of Organic Compounds

  • Carbohydrates
  • Lipids
  • Proteins
  • Nucleic Acids
• Carbohydrates


  Source of energy
• Carbohydrates

  • Sugars - simple carbohydrates - monosaccharides(glucose) and disaccharides
  • Polymers - complex carbohydrates
• Lipids

  Used for energy storage, build cellular structures, signal molecules (communication)
• Lipids

  • Cholesterol, paraffin, oils
• Proteins


  More complex organic compounds composed of carbon & lipids - build cellular structures, speed up biochemical reactions, package and transport materials, help replicate genetic material
• Peptides


  Chains of amino acids that proteins are made of
• Nucleic Acids


  Coding of the genetic info of an organism
• Nucleotide

  • Nitrogenous base
  • Sugar molecule
  • Phosphate group
• Types of Nucleic Acids

  • DNA (deoxyribonucleic acid)
  • RNA (ribonucleic acid)
• Mixtures consist of two or more substances that are combined physically, no chemical reaction
• Classification of Mixtures:

  1. Homogeneous Mixtures - consists of particles that are so small to be seen by the naked eye - also known as solutions - composed of a solute and a solvent
  2. Heterogeneous Mixtures - consists of particles that are not evenly distributed throughout - can be distinguished from each other
• miscible - liquids that are soluble in each other at all proportions - alcohol and water
• immiscible - oil and water
• aqueous solutions - solutions in which the solvent is water - wine, alcohol, soft drink (dissolved carbon dioxide)
• alloys - solid solutions, mixtures of metals with other metals or nonmentals - steel (iron+carbon) , brass (carbon+zinc)
• gaseous solution - unpolluted air - Nitrogen (78%) Oxygen (21%) Other gases (1%)
• Classifications of Heterogeneous Mixtures:

  1. Colloids - particles that are bigger than solution but smaller than suspension - particles do not settle - e.g. mayonnaise, hair gel, blood (*Tyndall effect - a phenomenon where light is scattered)
  2. Suspensions - suspended particles, large enough to be seen by naked eye - settle at bottom