Compounds Made of elements in a specific ratio that is always the same Has a chemical formula Can only be separated by chemical means, not physically
Pure Substances Element composed of identical atoms EX: copper wire, aluminum foil
Pure Substances Compound composed of 2 or more elements in a fixed ratio properties differ from those of individual elements EX: table salt (NaCl)
Pure Substances For example: compounds Two different compounds, each has a definite composition.
Mixtures Variable combination of 2 or more pure substances. Heterogeneous (Mechanical Mixture) Homogeneous (solution)
Mixtures: Homogenous Solution homogeneous very small particles no Tyndall effect Tyndall Effect –particles dont settle –EX: rubbing alcohol
Mixtures Mechanical Mixture Not of a uniform composition throughout Heterogenous
Mixtures: Heterogenous Suspension Heterogeneous When mixed, a suspension can look uniform particles settle = more than one distinct layer EX:fresh-squeezed lemonade
Mixtures vs. Compounds http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/elements_com_mix_6.shtml
Can you identify the following? You will be shown a series of photos. Tell if each photo represents an item composed of an element, compound, or mixture. Review: An element contains just one type of atom. A compound contains two or more different atoms joined together. A mixture contains two or more different substances that are only physically joined together, not chemically. A mixture can contain both elements and compounds.