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Presentation on theme: "BALANCING EQUATIONS & CHEMICAL REACTIONS."— Presentation transcript:


2 Evidence of Chemical Change
Changes in Energy (E) Release of E as heat Release of E as light Production of sound Reduction or increase of temperature Absorption or release of electrical Energy Formation of new substances Formation of a gas Formation of a precipitate Change in color Change in odor

3 Law of Conservation of Mass Same number of atoms on both
In any physical or chemical reaction, mass is neither created nor destroyed; it is conserved! Reactants Products Same number of atoms on both sides of the equation!

4 Balancing Equations In every balanced equation
each side of the equation has the same number of atoms of each element

5 Important stuff! Heat Pressure Temperature Catalyst
Four abbreviations are used to indicate physical states of chemicals: shown as subscripts in the chemical equation (s) = solid (l) = liquid (g) = gas (aq)= aqueous solution (dissolved in water) Symbols over the arrow indicate the conditions of the reaction Heat Pressure Temperature Catalyst Reversible reaction

6 Balance this equation…
NaNO3 + CrCl3  NaCl + Cr(NO3)3 How would you “write” it?

7 Combination Reaction or Synthesis Reaction
Two or more simple substances react to form a more complicated one A + B  AB Fe + S  FeS


9 Combination Reactions
We can predict the products of ionic compounds by thinking about the charge! Al (s) + O2 (g)  Cu (s) + S(s)  Are there 2 possible products to this reactions How would we “say” these equations?

10 Decomposition Reaction
A decomposition reaction is the opposite of a composition reaction - a complex molecule breaks down to make simpler ones. AB  A + B 2 H2O  2 H2 + O2


12 Decomposition Reactions
Harder to predict the products…always remember your diatomics. Water is often a product! HgO(s)  NH4NO3

13 Decomposition Reactions
HgO(s)  2HgO(s)  2Hg(l) + O2 (g) NH4NO3  NH4NO3  N2O + 2H2O The only way to really know is to do the reaction!!

14 Single Replacement This is when one element trades places with another element in a compound. A + BC  AC + B Mg + 2H2O  Mg(OH)2 + H2


16 Single Replacement Reactions
Easy to predict the products. Look at the ions… remember that a cation has to bond to an anion!! Don’t forget about diatomics! Zn(s) + H2SO4(aq)  Na(s) + H2O  OOPS! Did we balance them?

17 Single Replacement Reactions
Zn(s) + H2SO4(aq)  Zn(s) + H2SO4(aq)  ZnSO4(aq) + H2(g) Na(s) + H2O  Na(s) + H+OH-(l)  2Na(s)+ 2H+OH-(l)  2NaOH + H2(g)

18 Single Replacement Reactions
Reactivity of a metal makes a difference! If a metal is more reactive than the metal it is displacing a rxn will occur. If the metal is less reactive than the metal it is displacing, a rxn will not occur.

19 Metal Reactivity Increases down a group Decreases across a period

20 Brainiacs-- Metal Reactivity

21 Reactivity in Single Displacement
Cs KMnO4  CsMnO4 Will this occur?? Na KMnO4  NaMnO4 + K Will this occur?

22 Double Replacement Reaction
This is when the anions and cations of two different molecules switch places, forming two entirely different compounds AB + CD  AD + CB Pb(NO3)2 + 2KI  PbI2 + 2KNO3


24 Double Replacement Reactions
Generally take place between two ionic compounds in aqueous solution Pb(NO3)2 + 2KI  PbI2 + 2KNO3

25 Double Replacement Reactions
2NaCl + H2SO4 

26 Double Replacement Reactions
Ca(OH)2(aq) + 2HCl(aq) )

27 Combustion Reactions A combustion reaction is when oxygen combines with another compound or element producing energy. When hydrocarbons (C?H?) combust, water, carbon dioxide and energy are produced. C10H O2  10 CO2 + 4 H2O + Energy Combustion of Naphthalene

28 Combustion Reactions Combustion of propane: C3H8 + O2 
Combustion of methane: CH4 + O2  Combustion of butene (this one is tricky!) C4H O2 

29 Teacher Demo Extraordinaire!

30 What is a flame video- Science Friday

31 Recap: 5 Types of Reactions
Combination Decomposition Single Replacement Double Replacement Combustion

32 Warm Up: Predict the products, balance and classify the following reactions.
Li + MgCl2  C6H O2  Ca(NO3) NaOH 

33 Types of Rxns Lab Take about 10 minutes to do the prelab questions on the lab. Most of the answers should be in your CB notes.

34 Warm Up- Balance the following combustion equations:
C4H O2  CO2 + H2O C3H O2  CO2 + H2O C7H O2  CO2 + H2O

35 Types of Reaction Lab a. Synthesis: Mg + O2 b. Decomposition CuCO3
c. Single Replacement Zn + HCl d. Double Replacement PbNO3 + KI

36 Finish the lab You have 20 minutes to get it done! Be sure that all your questions are answered!

37 Debrief Types of Rxns Lab

38 Types of Reaction Lab Synthesis: Mg + O2 
Did the mass of the system change after the reaction took place? Did you detect the presence of ammonia gas? Endothermic or exothermic? Mass should be greater- MgO Mg + N yields Mg3N2 Mg3N2 + H2O yields Mg(OH)2 + NH3

39 Types of Reaction Lab Decomposition CaCO3 
What evidence indicates a chemical reaction. How do you know that carbon dioxide was formed? Endothermic or exothermic?

40 Types of Reaction Lab Single Replacement Zn + HCl 
What evidence did you see? What was in the little tube– how do you know? Endothermic or exothermic?

41 Types of Reaction Lab Double Replacement PbNO3 + KI 
What evidence did you see? Endothermic or exothermic?

42 Work on classifying the types of reactions on your balancing WS.
When you finish, you can start working on the back side of the Current Mole WS…. The front side should be complete!

43 Warm Up Balance and classify the following reactions:
Zn H2SO4 → H Zn(SO4)2 CaCl NaNO3 → Ca(NO3) NaCl C3H O2 → CO H2O

44 You should have most of these WS done!
Balancing equations WS– classified rxn type 2. Mole Practice WS… Finish both of these… turn them in! Work on the Review! Due the beginning of class on Monday! Test after we go over the review!!

45 Warm Up Balance and classify the following reactions:
Na H2CO3 → H Na2CO3 2. NaF Ca(NO3)2 → NaNO CaF2 3. C5H O2 → CO H2O

46 Warm Up- part 2 Determine the molar mass of MgF2 Convert 5.7 g of magnesium fluoride to moles. Convert 6.3 g of magnesium fluoride to molecules.

47 Warm Up Quiz Determine the molar mass of Na3PO4
How many moles in 10.6g of Na3PO4 How many atoms in 0.50 mol Al? How many atoms in 3.6 g of carbon?

48 Warm Up Balance and classify the following reactions:
K H3PO4 → H K3PO4 3. CH O2 → CO H2O


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