Investigating Chemical Reactions! Science 10 Investigating Chemical Reactions!

Chemical Reactions Magnesium (Mg) and Oxygen (O2) Before Burning: Mg: silver colour, lightweight, metal. O2: invisible gas in air. After burning: white powder.

Chemical Reactions A chemical reaction is the process that leads to a chemical change in which new substances with new properties are formed. They can be summarized 2 ways…

Chemical Reactions 1. As a word equation i.e.: magnesium plus oxygen react to produce magnesium oxide. Or a generic equation: reactant(s) yield(s) product(s) 2. As an equation using formulas: i.e.: Mg + O2 → MgO

Antoine Lavoisier Who?: When?: Where?: French Nobleman (aristocracy) Wealthy family Tax collector before the French Revolution Beheaded during the Revolution (1794) during the Reign of Terror. When?: Late 1700’s, during the French Revolution Where?: France

Antoine Lavoisier Discoveries he made: 1. Named oxygen and hydrogen as elements. 2. Helped develop the metric system. 3. Developed the “Law of Conservation of Mass”.

The Law of Conservation of Mass In any chemical reaction the total mass of the reactants will always equal the total mass of the products. (As long as the reaction is closed) What goes in, must come out! Mass is neither lost nor gained in a chemical reaction!!!

The Law of Conservation of Atoms In any chemical reaction, atoms are neither created nor destroyed. So…Mg + O2 → MgO is not a balanced reaction.

Assignment C.Y.U. 9.1 p. 234. # 1,2,5,6,8,9 in point form. # 4 & 7 in complete sentences.

Balancing Chemical Equations Let’s combine sodium and chlorine in a chemical equation: Na + Cl2 → NaCl Reactants yield products This is a skeleton equation; correct formula, but it is not balanced. Note: chlorine is a diatomic element. What are the other diatomic elements? -Cl2, H2, N2, O2, F2, Br2, I2

Balancing Chemical Equations All chemical equations must obey 2 laws of basic chemistry: The law of conservation of atoms In any chemical reactions, atoms are neither created nor destroyed. The law of conservation of mass In any chemical reaction, the mass of the reactants always equals the mass of the products,

Balancing Chemical Equations Let’s balance the equation: Na + Cl2 → NaCl The balanced equation must have the same number of Na and Cl on each side: 2Na + Cl2 → 2NaCl Let’s see how this is done…

Balancing Chemical Equations 1. Cu2S + O2 → Cu2O + SO2 How many Cu atoms are in the reactants? ___ in the products?___ What coefficient(s) will make the number of Cu atoms in the reactants and products equal?___ How many S atoms are in the reactants?___ What coefficient(s) will make the number of S atoms in the reactants and products equal?___

Balancing Chemical Equations Cu2S + O2 → Cu2O + SO2 How many O atoms are in the reactants? in the products?___ What coefficient(s) will make the number of O atoms in the reactants and products equal?___ Do any coefficients need to be changed? ___ Rewrite the equation and balance: 2Cu2S + 3O2 → 2Cu2O + 2SO2

Balancing Chemical Equations So when balancing a chemical equation ask yourself: How many atoms of each element are in the reactants? How many atoms of each element are in the products? What coefficients do I need to make the equal? You might need to use lowest common multiples to figure it out. You might need to add coefficients to elements that started out equal.

Balancing Chemical Equations

Balancing Chemical Equations

Balancing Chemical Equations