REMEMBER: An element is made of only ONE kind of atom Most atoms found in nature ARE NOT found as elements, but instead found as COMPOUNDS Compound - a substance composed of two or more elements that are chemically combined to form a new substance with new properties. Table salt is a compound
Your body is made of many compounds: Water - 60% of your body Proteins - make up skin, bones, tendons, ligaments Membranes - surround cells DNA - determines the traits you inherit
What’s the difference between a particle & an element? Each particle of a compound is made of EXACTLY the same ratio of elements. EXAMPLES : Every particle of table salt contains ONE atom of Sodium combined with ONE atom of Chloride. Every particle of water is made with TWO atoms of Hydrogen combined with ONE atom of Oxygen. Properties differ as well. – Sodium Chloride (table salt) has different properties than Sodium & Chlorine. Chlorine - greenish yellow, poisonous gas Sodium - silvery white metal Sodium Chloride - white grains that add flavor to your foods
Chemical Formulas Scientists not only use symbols for elements, they also use them for compounds. Every compound has ITS OWN chemical formula <ul><li>Consists of 2 parts: </li></ul><ul><li>Symbols for the elements </li></ul><ul><li>Subscripts (numbers)- number of atoms for each element in the compound </li></ul>Examples: H 2 O = Water NaCl = Sodium Chloride C 6 H 12 O 6 = glucose (type of sugar) A subscript of 1 is NEVER written in a formula. If there is no number, there is only ONE atom of that element.
Let’s look at some more compounds! FeO 3 - Iron Oxide(rust)- 2 elements (1 Iron, 3 Oxygen) Total- 4 atoms CuSO 4 - Copper sulfate- 3 elements (1Copper, 1 Sulfur, 4 Oxygen) Total- 6 atoms H 2 SO 4 - Sulfuric Acid(battery acid)- 3 elements (2Hydrogen, 1 Sulfur, 4 Oxygen) Total 7 atoms CaCO 3 - Limestone(Chalk)- 3 elements (1 Calcium, 1 Carbon, 3 Oxygen) Total- 5 atoms
Mixtures Elements & compounds are only 2 ways matter can be classified. Another way is MIXTURES Mixture - combination of substances in which the atoms ARE NOT chemically combined. - can be a combination of elements, compounds or both - retain their properties -can be easily separated using the physical properties it contains