2.  Balanced Chemical Equation – a representation of a chemical reaction using symbols that show the same number of atoms of each element on both sides of the reaction arrow  Coefficients – whole numbers written in front of a chemical symbol to represent the number of moles of that substance  Reactants – the chemical substances that are present before a chemical reaction starts; typically written on the left side of the arrow  Products - the chemical substances that are present after a chemical reaction occurs; typically written on the right side of the arrow  Subscripts – the whole numbers written to right and below the symbol for that element indicating how many atoms of that substance are present in the substance

3.  Release of a gas  Evidence - Bubbles  Change in temperature  Evidence – Temperature goes up (exothermic)  Evidence – Temperature goes down (endothermic)  Change in color  Evidence - solution changes color  Formation of a precipitate  Evidence - forms and settles to the bottom  Energy is released  Evidence - light or sound

4. SymbolMeaning of Symbol (s)A reactant or product in the solid state; also used to indicate a precipitate (l)(l)A reactant or product in the liquid state (g)(g)A reactant or product in the gaseous state (aq)A reactant or product in an aqueous solution (dissolved in water) → Used to indicate the direction of a reaction. Translated as “yields” of “produces”.

5.  Synthesis  Decomposition  Single Replacement  Double Replacement  Combustion

6. Generic Form:A + B → AB Reactants: A and B are either elements or simple compounds Products: AB is a complex compound formed from A and B All Synthesis Reactions involving uncombined elements are REDOX Reactions Reaction Mechanism: The atoms of A and B are bonded together to form a single new compound

7. 2 Na + Cl 2 → 2 NaCl › Sodium atoms and chlorine gas molecules combine to form a single new product › Sodium chloride is the product of the reaction 2 Mg + O 2 → 2 MgO › Magnesium atoms and oxygen gas molecules combine to form a single new product › Magnesium oxide is the product of the reaction › In a moment, we will also see that this reaction can also be classified as a combustion reaction

8. Generic Form:AB → A + B Reactants: AB is a complex compound formed from A and B Products: A and B are either elements or simple compounds All Decomposition Reactions involving uncombined elements are REDOX Reactions Reaction Mechanism: The compound AB breaks down into its elements or into simple compounds

9. 2 H 2 O 2 → 2 H 2 O + O 2 › Hydrogen peroxide molecules break down to form new products that are simple molecules › Water and oxygen gas are the products of the reaction 2 KClO 3 → 2 KCl + 3 O 2 › Potassium chlorate molecules break down when heated to form new products that are simple molecules › Potassium chloride and oxygen gas are the products of the reaction

10. Generic Form: A + O 2 → H 2 O + CO 2 Reactants: A is a hydrocarbon (a compound of hydrogen and carbon) O 2 is oxygen gas (we will assume more than enough oxygen is present) Products: When combusting a hydrocarbon, the products will always be water and carbon dioxide All Combustion Reactions are REDOX Reactions Reaction Mechanism: The hydrocarbon is oxidized and produces energy With a hydrocarbon the reaction is generally rapid

11. C 2 H 4 + 3 O 2 → 2 CO 2 + 2 H 2 O › Ethene (also known as acetylene) is a hydrocarbon › When O 2 is a reactant, the reaction must be combustion › The products must be water and carbon dioxide

12. Generic Form:A + BY → AY + B Reactants: A is a metal element BY is an ionic compound Products: AY is an ionic compound B is a metal element or a diatomic molecule All Single Replacement reactions are REDOX & Precipitation Reactions Reaction Mechanism: A and B are elements of the same type If A is more reactive than B, the reaction occurs with A replacing B If A is less reactive than B, no reaction can occur

13. 2 Al (s) + 3 CuCl 2(aq) → 2 AlCl 3(aq) + 3 Cu (s) Aluminum is a metal and copper is the metal in the ionic compound Aluminum is more reactive than copper, therefore the reaction occurs The aluminum replaces the copper ion in the ionic compound and the element copper forms as a precipitate What happens if the reaction is reversed? Cu (s) + AlCl 3(aq) → No reaction occurs The copper is not more reactive than the aluminum, so no reaction occurs

14. Generic Form:AX + BY → AY + BX Reactants: AX is an ionic compound BY is an ionic compound Products: AY is an ionic compound BX is a an ionic compound All Double Replacement reactions are Precipitation Reactions, but none are REDOX Reactions Reaction Mechanism: A and B are elements of the same type (both are metals ) as are X and Y (both are non-metals) A replaces B and X replaces Y (the ions trade partners) If an insoluble product (precipitate or insoluble gas) is produced, the reaction occurs

15. Na 2 SO 4(aq) + Ba(NO 3 ) 2(aq) → 2 NaNO 3 (aq) + BaSO 4(s) The ions in the two ionic compounds change partners and form two new ionic compounds BaSO 4 is not soluble in water BaSO 4 is the product of the reaction What happens if there is no precipitate? Na 2 SO 4(aq) + KNO 3 (aq) → No Reaction The ions of sodium, potassium, sulfate, and nitrate cannot produce an insoluble product Therefore, there is no product of the reaction and that means there is no reaction between the sodium sulfate and the potassium nitrate

16.  Reduction-Oxidation (REDOX) Reactions › Electrons migrate resulting in a change in oxidation numbers  Precipitation › A solid product is produced as a result of the reaction  Strong Acid-Base Neutralization › Reactions produce water & a salt

17. TYPEREDOX (migration of electrons) PRECIPITATION (solid product formed) ACID-BASE NEUTRALIZATION Synthesis When an uncombined element is present Only when two gases combine to form a solid Never DecompositionWhen an uncombined element is present Never CombustionAlwaysNever Single Replacement AlwaysWhen metal replaces metal Never Double Replacement NeverAlways (Special Case: gas is produced) When reactants are acids & bases

18. Mass cannot be created or destroyed in chemical reactions Matter can be and is changed by the rearrangement of atoms, but the mass cannot change Therefore, the same atoms of matter still exist after a chemical reaction as were present before the reaction

19. Equations describe chemical reactions showing the reactants and products Since mass must be conserved, the same number of atoms of each element must be present in the products as were in the reactants Individual atoms do not react alone – many atoms react at the same time Atoms are counted using moles The number of moles of each reactant and product must be adjusted to have the same number of atoms on both sides of the reaction That process is known as balancing the reaction

20. It is a process of counting atoms The chemical formula of the compounds or elements cannot be changed – you may not change anything about the reactants or the products themselves Only the coefficients (the number of moles) can be changed Changing the number of moles (coefficients), changes the number of atoms of every element in the compound Coefficients (moles) are changed until the same number of each atom are on both sides of the reaction

21. List the elements involved in the reaction Count the number of moles of each element on both sides of the reaction Adjust the number of moles using coefficients so that the first element is balanced Recount the number of moles of each element Repeat the process until the same number of moles is present for every element in the reaction Check the result to make sure that the balanced reaction is the lowest whole number ratio of the reactants and products