I can read and understand the information contained within a chemical reaction.

Reaction Types

I can read and understand the information contained within a chemical reaction

Learning Target 1

Chemical reactions involve changes in matter, the making of new materials with new properties, and energy changes.

In a given reaction ….Symbols represent elements (H)Chemical formulas describe compounds (Al2O3)

Introduction

◦ Chemical equations show the conversion of reactants (on the left of the arrow) into products (on the right of the arrow).

“+” sign separates molecules on the same side The arrow is read as “yields”

ExampleC + O2 CO2

This reads “carbon plus oxygen yields carbon dioxide”

Parts of a Reaction Equation

The charcoal used in a grill is basically carbon. The carbon reacts with oxygen to yield carbon dioxide. The chemical equation for this reaction, C + O2 CO2, contains the same information as the English sentence but has quantitative (numerical) meaning as well.

Chemical reactions depict the kind of reactants and products in a given chemical reaction and their relative amounts. Reactants are “what goes in” and Products are “what comes out!”

4 Al + 3 O2 → 2 Al2O3

The numbers in the front are calledcoefficients.

Chemical Reactions

The coefficient in front of a given element in an equation can stand for a representative particle (one piece) of the substance OR a mole of the substance

4 Al + 3 O2 ---> 2 Al2O3

4 atoms of aluminum plus 3 molecules of oxygen gas yield

two molecules of aluminum oxide OR

4 moles of aluminum plus 3 moles of oxygen gas yieldtwo moles of aluminum oxide

What coefficients mean …

(l) “liquid”; this indicates that a chemical is in liquid form. EX: H2O(l)

(aq) “aqueous”; this indicates that a chemical is dissolved. EX: NaCl (aq)

(g) “gaseous”; this indicates that a chemical is in gaseous form. EX: CO2(g)

(s) “solid”; this indicates that a chemical is in solid form. EX: Mg(OH)2(s)

“precipitate”; this indicates that a product is a solid precipitate. EX: CaCO3

“delta” or “heat”; this symbol over the yields sign indicates that heat is added to move the reaction along.. EX: ↑ “gas”; this indicates that a product is formed which is a gas, and forms bubbles. EX: H2↑

Other Reaction Symbols

I can differentiate between the different types of chemical reactions.

Learning Target 2

〉How does learning about reaction types help in understanding chemical reactions?

〉You can use patterns to identify kinds of chemical reactions and to predict the products of the chemical reactions.

Classifying Reactions

There are five types of chemical reactions we will talk about:

1. Synthesis reactions2. Decomposition reactions3. Single replacement reactions4. Double replacement reactions5. Combustion

You need to be able to identify the type of reaction

Types of Reactions

Synthesis reactions occur when two substances (generally elements but sometimes compounds) combine and form a compound

reactant + reactant 1 product

• A + B AB• Example: 2H2 + O2 2H2O • Example: C + O2 CO2

1. Synthesis Reactions

• Here is another example of a synthesis reaction

Synthesis Reactions

• Decomposition reactions occur when a compound breaks up into the elements or into a few simpler compounds

1 Reactant Product + Product In general: AB A + B• Example: 2 H2O 2H2 + O2• Example: 2 HgO 2Hg + O2

2. Decomposition Reactions

• Another view of a decomposition reaction:

Decomposition Reactions

Single Displacement Reactions occur when one element replaces another in a compound.

• A metal can replace a metal OR a nonmetal can replace a nonmetal.

• element + compound product + product A + BC AC + B (if A is a metal) ORA + BC BA + C (if A is a nonmetal)

3. Single Replacement Reactions

• Sodium chloride solid reacts with fluorine gas NaCl(s) + F2(g) NaF(s) + Cl2(g)

Note that fluorine replaces chlorine in the compound

• Aluminum metal reacts with aqueous copper (II) nitrate

Al(s)+ Cu(NO3)2(aq) Cu(s) + Al(NO3)3(aq)

Single Replacement Reactions

• Another view:

Single Replacement Reactions

• Double Replacement Reactions occur when a metal replaces a metal in a compound and a nonmetal replaces a nonmetal in a compound

Compound + compound product + productAB + CD AD + CB

4. Double Replacement Reactions

Think about it like “foil”ing in algebra, first and last ions go together + inside ions go together

Example:• AgNO3(aq) + NaCl(s) AgCl(s) + NaNO3(aq)

• Another example:K2SO4(aq) + Ba(NO3)2(aq) KNO3(aq) + BaSO4(s)

Double Replacement Reactions

5. Combustion Reactions• Combustion reactions

occur when a hydrocarbon reacts with oxygen gas. These always produce CO2 and H2O as products.

• In order to burn something you need the 3 things in the “fire triangle”:1) A Fuel (hydrocarbon)2) Oxygen to burn it with3) Something to ignite the reaction (spark)

• Examples• C5H12 + O2 CO2 + H2O

and

Combustion

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