Posters

1. Signs of a chemical reaction2. Chemical vs. Physical reaction3. Symbols used in chemical reactions4. Synthesis5. Decomposition6. Single diplacement7. Double displacement8. 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 55 Types of Reactions

We classify reactions into 5 categories so that we may more

easily predict the products.

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Synthesis DefinitionSynthesis 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 2MgOMagnesium and oxygen combine to form

magnesium oxide.

2H2 + O2 2H2OHydrogen 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

Decomposition

2 H2O 2H2 + O2

Water decomposing into hydrogen gas and

oxygen gas.

Decomposition of H2O2MENU

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

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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

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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– Ex: 2 H2

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

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