Regents chemistry textbook page 28 #1-14 1) Two types of pure substances are elements and compounds. 2) Compound – two or more different elements chemically combined. 3) An element is made up of one type of atom whereas a compound is composed of two or more different elements chemically combined. 4) Atoms and molecules are both pure substances. Molecules are made up of atoms chemically combined. Diatomic molecules (Br2 I2 N2 Cl2 H2 O2 F2) are elemental because they are composed of one type of atom. 5) The smallest number of elements needed to make a compound is TWO.  CO  HCl  HF  FeS  H2O 6) Compounds 1) Two or more different elements chemically combined. 2) The ratio of elements in a specific compound are fixed and always occur in this ratio.  FeS ( 1 iron to 1 sulfur)  CuSO4 (1 copper to 1 sulfur to 4 oxygen) 3) Compounds can be broken down chemically, but not physically. 7 a) CH4: compound b) S8: element Mixtures 1) Two or more different atoms and or compounds physically combined. 2) No set ratio. 3) Can be heterogeneous or homogeneous. 4) Mixtures are broken down physically not chemically. c) distilled water: compound d) salt water (NaCl(aq)): homogeneous mixture or solution e) CH2O: compound f) concrete: heterogeneous mixture 8) Homogeneous mixture or solution – physical combination of atoms and or compounds evenly distributed throughout so only one phase is present. NaCl (aq) CO2(aq) ***Remember (aq) means aqueous solution, so the substance is completely dissolved in water Heterogeneous mixture – physical combination of atoms and or compounds not evenly distributed. 2 or more phases will be present. 9) Compounds are not monatomic because they are composed of at least 2 different elements chemically combined. 10) The sucrose composition is the same. Both sucrose molecular compounds have a fixed ratio of elements. 11) The resulting material is a new compound with new chemical and physical properties. Fe(s) + S(s) + heat  FeS(s) 12) Use the water displacement test to calculate the density of each ring. 13) The dissolved spoonful of sugar is a homogeneous mixture or solution because all the sugar particles are distributed evenly throughout the mixture in one phase. There should be no solid sugar particles sitting on the bottom of the glass. C6H12O6(aq) is an aqueous solution. 14) C + O2 is a heterogeneous mixture. CO is a compound. CO2 is a compound. Co is an element.