EVIDENCES OF A CHEMICAL REACTION 1 Color change

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EVIDENCES OF A CHEMICAL REACTION: 1) Color change. 2) Formation of a solid (precipitate).

EVIDENCES OF A CHEMICAL REACTION: 1) Color change. 2) Formation of a solid (precipitate). 3) Evolution of a gas (bubbles). 4) Temperature changes (exothermic or endothermic).

During a chemical reaction the reactants collide breaking the chemical bonds between their particles

During a chemical reaction the reactants collide breaking the chemical bonds between their particles & the atoms are rearranged forming new bonds (new substances): HH H 2 HH O H HH O + H HH HH O 2 (Chemical Equation) HH O 2 H 2 O H HH HH O

In a chemical reaction, one or more reactants change into one or more products.

In a chemical reaction, one or more reactants change into one or more products. Reactants yield Products 2 Na. OH (aq) + Cu. SO 4 (aq) → Na 2 SO 4 (aq) +Cu(OH)2 (s) A chemical equation is a representation of a chemical reaction (model). (aq) aqueous (dissolved in water). (g) gas. (s) solid (precipitate). (l) liquid.

Law of Conservation of Mass vs Chemical equations: H 2(g) + Br 2(g) →

Law of Conservation of Mass vs Chemical equations: H 2(g) + Br 2(g) → 2 (1 g) + 2 (79. 9 g) → 161. 8 g ≠ 161. 8 g = 2 HBr (g) (1 g + 79. 9 g) 2(80. 9 g ) 161. 8 g The mass is conserved. Always !

Law of Conservation of Mass The mass is neither created nor destroyed. The total

Law of Conservation of Mass The mass is neither created nor destroyed. The total mass of all substances before a chemical change (reactants) equals the total mass of all substances remaining after the change (products).

Law of Conservation of Mass Example 1: 2 Mg (s) + O 2 (g)

Law of Conservation of Mass Example 1: 2 Mg (s) + O 2 (g) → 2 Mg. O (s) 24 g + 16 = ?

Law of Conservation of Mass Example 1 : 2 Mg (s) + O 2

Law of Conservation of Mass Example 1 : 2 Mg (s) + O 2 (g) → 2 Mg. O (s) 24 g + 16 = 40 g

Law of Conservation of Mass Example 2: 2 Mg (s) + O 2 (g)

Law of Conservation of Mass Example 2: 2 Mg (s) + O 2 (g) → 2 Mg. O (s) 12 g + ? = 20 g

Law of Conservation of Mass Example 2: 2 Mg (s) + O 2 (g)

Law of Conservation of Mass Example 2: 2 Mg (s) + O 2 (g) → 2 Mg. O (s) 12 g + 8 g = 20 g

Law of Conservation of Mass Example 2: 2 Mg (s) + O 2 (g)

Law of Conservation of Mass Example 2: 2 Mg (s) + O 2 (g) → 2 Mg. O (s) 12 g + 8 g = 20 g x = 20 g – 12 g x=8 g

Law of Conservation of Mass Example 3: Na. OH (aq) + HCl (aq) →

Law of Conservation of Mass Example 3: Na. OH (aq) + HCl (aq) → Na. Cl (aq) + H 2 O 40 g + 36. 5 g = 58. 5 g + ?

Law of Conservation of Mass Example 3: Na. OH (aq) + HCl (aq) →

Law of Conservation of Mass Example 3: Na. OH (aq) + HCl (aq) → Na. Cl (aq) + H 2 O 40 g + 36. 5 g = 58. 5 g + 18 g

Law of Conservation of Mass Example 3: Na. OH (aq) + HCl (aq) →

Law of Conservation of Mass Example 3: Na. OH (aq) + HCl (aq) → Na. Cl (aq) + H 2 O 40 g + 36. 5 g = 58. 5 g 76. 5 g = 58. 5 g + x x = 76. 5 g – 58. 5 g x = 18 g + 18 g