Mixtures and pure substances - Pure substances are matter made up of only one type of atom or molecule - Mixtures are a collection of 2 or more pure substances physically mixed together that cannot be represented by a chemical formula. - A mixtures properties may vary, because the proportions of the substances in them may vary. Gold for example is too soft to maintain it's shape in jewelry so copper silver, or nickel is usually added to create more hardness in the god this solid mixture is known as an alloy. - Pure substances have specific chemical and physical properties. Pure substances are often hard to find so if a substance is mixed with small amounts of impurities the substance is still considered to be pure.- Mixtures may be classified as either homogeneous or heterogeneous. Homogeneous mixtures are ones where substances are uniformly distributed throughout. Gas, syrup, and saltwater are homogeneous mixtures. Heterogeneous mixtures contain substances which are not evenly distributed throughout. A salad, cereal, and Snickers bars are heterogeneous mixtures. - Mixtures contain phases in which part of a system has uniform composition and properties. Elements- Elements are the simplest pure substances, since they contain only one kind of atom. - Every element has a set of chemical and physical properties, purified gold discovered today cannot be distinguished from gold found years ago because pure gold from any source is the same substance, an unreactive soft metal which melts at 1064C.- There are over 109 elements but only about 12 make up things we see everyday. Hydrogen is the most common of all it makes up more than 90% of the atoms of the known universe. Oxygen and silicon make up over 70% of the Earth's crust. - Living things a mainly made up of four elements, those being carbon, oxygen, hydrogen, and nitrogen, these combine to create the molecules needed for life. - Allotropes are different molecular forms of a...
