Posters Signs of a chemical reaction Chemical vs. Physical reaction Symbols used in chemical reactions Synthesis Decomposition Single diplacement Double displacement Combustion

Journal Entry How were these rocks formed?

Signs of a chemical reaction Production of…. Heat Light Gas Precipitate (solid formed from two liquids) Color change

The 5 Types of Reactions We classify reactions into 5 categories so that we may more easily predict the products. NEXT

A + B  AB  + Synthesis Definition Synthesis reaction – 2 substances are combined to form a single product Combination reactions may also be called composition or synthesis reactions. A + B  AB  + MENU

Synthesis Examples 2Mg + O2  2MgO Magnesium and oxygen combine to form magnesium oxide. 2H2 + O2  2H2O Hydrogen and oxygen combine to form dihydrogen monoxide (water) MENU

Synthesis Demonstration Zinc + Sulfur  Zinc Sulfide Zn + S  ZnS Observations:

Decomposition Definition Decomposition reaction – A single compound is broken down into 2 or more products. AB  A + B +  MENU

Decomposition Examples 2NaCl(s)  2Na(s) + Cl2(g) Sodium chloride (table salt) decomposes into sodium and chlorine gas. CaCO3  CaO + CO2 Limestone (CaCO3 ) decomposes into lime (CaO) and carbon dioxide. MENU

Water decomposing into hydrogen gas and oxygen gas. Decomposition 2 H2O  2H2 + O2 Water decomposing into hydrogen gas and oxygen gas. Decomposition of H2O2 MENU

Decomposition Demonstration C12H22O11 + H2SO4 → C + H2O + SO2 (balance this!) Sugar + Sulfuric acid  Pure carbon + Water + Sulfur dioxide Observations:

Decomposition Demonstration 2 NaHCO3 --> Na2CO3 + H2O + CO2 Observations: Massinitial Massfinal

Combustion Definition Combustion reaction – Hydrogen or a hydrocarbon (H and C) burn in oxygen to produce water and carbon dioxide. Heat is given off as energy. CxHx + O2  XH2O + XCO2 MENU

Combustion Examples CH4 + 2O2  2H2O + CO2 Methane burns in oxygen to produce water and carbon dioxide. C12H22O11 + 12O2  11H2O + 12CO2 A sugar molecule burns in oxygen to produce water and carbon dioxide. MENU

Combustion demonstration Ethanol + Oxygen yields Water + Carbon dioxide C6H12O6 + O2  H2O + CO2

Single Replacement Definition Single Replacement reaction – A single element takes the place of an element in a compound. A + BC  B + AC + +  MENU

Single Replacement Examples Mg + BeO  Be + MgO Magnesium replaces beryllium in beryllium oxide to form magnesium oxide and beryllium. 2Na + 2HCl  H2 + 2NaCl Sodium replaces hydrogen in hydrochloric acid to yield hydrogen and sodium chloride. MENU

Single Replacement Demo. A single replacement of Zinc metal for hydrogen in hydrochloric acid. Zn + 2HCl  H2 + ZnCl2

Double Replacement Definition Double Replacement reaction – Elements in 2 compounds switch places to form 2 new compounds. AB + CD  AD + CB + +  MENU

Double Replacement Examples MgO + BeS  MgS + BeO Oxygen and sulfur switch places to form magnesium sulfide and beryllium oxide. Na2S + Zn(NO3)2  2Na(NO3) + ZnS Sulfur and nitrate switch places to form sodium nitrate and zinc sulfide.

Make a Venn diagram comparing…. Synthesis vs. Decomposition Single replacement vs. double replacement

What type of reaction? 2 H2 + O2 -- 2H20

What type of reaction? A + BX  AX + B

What type of reaction? AgNO3 + CuSO4  AgSO4 + CuNO3

What type of reaction is this? 2 HCl (aq) + Zn (s) --> ZnCl2 (aq) + H2 (g)

What type of reaction?

Counting atoms How many Carbons are in each of the following compounds: CO2 C2H6 Na(CO3)2 Mg(C2O)4

Warm-up Around the room there are _7__ pictures representing types of reactions. YOUR pictures. Make a list in your notebook, 1- _7__. Try to determine what type of reaction is being represented by the drawing.

Definitions Co-efficient: The number before an element/compound (allowed to change when balancing) Ex: 2 H2 Subscript: The small number after an element/compound (NEVER allowed to change when balancing

Sacrificial Gummy Bear Demonstrates: Two types of chemical reactions HIGHLY Exothermic energy change Chemical energy converted into thermal, radiant and sound energy

Chemicals used KClO3 - Potassium chlorate C12H22O11 - Sucrose

First reaction KClO3 (s)  KCl (l) + O2 What type of reaction is this?

First reaction KClO3 (s)  KCl (l) + O2 Is this reaction balanced? (Make an RT table)

First reaction KClO3 (s)  KCl (l) + O2 Balance it!

First reaction 2 KClO3 (s)  2 KCl (l) + 3 O2 (g)

First reaction 2 KClO3 (s)  2 KCl (l) + 3 O2 (g)

Second reaction C12H22O11 + O2 (g)  C (s) + CO2 (g) + H2O (g) What type of reaction is this?

Second reaction C12H22O11 + O2 (g)  C (s) + CO2 (g) + H2O (g) Is it balanced? (Make an R/P table) If not, balance it! (1 min. early release if done correctly!)

Second reaction Balanced equation C12H22O11 + 3 O2  9 C + 3 CO2 + 11 H2O Balanced equation

Exothermic Reactions which release energy ∆H = 5635 kJ

How to balance equations 1.) Create a “R/P” table (Reactants vs. Products) 2.) Add coefficients to create equal numbers 3.) update the R/P table 4.) Change co-efficients until R = P

Pre-lab/practice Purpose: To generate hydrogen gas To set norms of behavior when dealing with acid

Norms:

Locations Ring stands are on top of fume hood Clamps are in 4A All other materials are on counter by sink 1

Materials Ring stand/clamp Test tube 1-2 pea-size chunks of Zn 1 bottle of HCl

Procedure Set up your apparatus as demonstrated Add the Zinc to the test tube Add approximately 2-4 cm of HCl to the test tube Cover with a small piece of aluminum foil Look for signs of a chemical reaction Allow to react for 3-4 minutes

Test Raise your hand when time has elapsed Use the flame test to look for signs of H2 gas

Clean up All test tubes must be cleaned out with Alconox Make sure that all acid is flushed with a large amount of water Sinks are to be totally clean

Homework reminder Read and take notes on pages 256-264 Answer questions 1 and 2 Due next class