Ch. 10.1 – Chemical Reactions Intro to Reactions read: (p. 276 – 280)

A.Signs of a Chemical Reaction Evolution of heat and light Formation of a gas Formation of a precipitate Color change

B.Law of Conservation of Mass mass is neither created nor destroyed in a chemical reaction total mass stays the same atoms can only rearrange 4 H 2 O 4 H 2 O 36 g 4 g 32 g

C. Chemical Equations A+B  C+D REACTANTS PRODUCTS

C. Chemical Equations p. 278

2H2(g) + O2(g)  2H2O(g) D. Writing Equations Identify the substances involved. Use symbols to show: How many? - coefficient Of what? - chemical formula In what state? - physical state Remember the diatomic elements.

Diatomics: N2 O2 F2 Cl2 Br2 I2 H2 Start with element #7 Form a figure 7 There are 7 of them – include Hydrogen       

D. Writing Equations 2 Al (s) + 3 CuCl2 (aq)  3 Cu (s) + 2 AlCl3 (aq) Two atoms of aluminum react with three units of aqueous copper(II) chloride to produce three atoms of copper and two units of aqueous aluminum chloride. How many? Of what? In what state? 2 Al (s) + 3 CuCl2 (aq)  3 Cu (s) + 2 AlCl3 (aq)

E. Describing Equations Describing Coefficients: individual atom = “atom” covalent substance = “molecule” ionic substance = “unit” 3CO2  2Mg  4MgO  3 molecules of carbon dioxide 2 atoms of magnesium 4 units of magnesium oxide

E. Describing Equations Zn(s) + 2HCl(aq)  ZnCl2(aq) + H2(g) How many? Of what? In what state? One atom of solid zinc reacts with two molecules of aqueous hydrochloric acid to produce one unit of aqueous zinc chloride and one molecule of hydrogen gas.

Writing Word Equations 1. When one unit of beryllium chloride reacts with 2 units of silver nitrate dissolved water, the reaction yields one unit of aqueous beryllium nitrate and 2 units of silver chloride powder. 2. When one molecule of fluorine gas is put into contact with one atom of calcium metal at high temperatures, one unit of calcium fluoride powder is created. 3. Two units of sodium nitrate react with one unit of lead (II) oxide to produce one unit of lead (II) nitrate and one unit of sodium oxide.