Chemical Reactions

New Substances produced by changing the way atoms are arranged

Physical Changes ≠ Chemical ReactionEvidence

Change in Color (rust)Temperature Change (endo/exo-thermic)Formation of a GasFormation of a Solid (Precipitate)

Chemical Reactions

Reactants: Substances Present @ BeginningProducts: Substances Formed by the ReactionYields: An “equal sign” in a

chemical reaction meaning “produces”, “creates”, or “forms”…

Na + Cl2 NaCl

Reactants Yields Products

Reaction Classifications

…Combining Elements…

A + B AB

Mg + O2 MgO

Synthesis

…Separating Elements…

CD C + D

H2O H2 + O2

(+Electricity)

Decomposition

…FIRE! (Needs Oxygen and produces CO2 )…

EF + O2 H2O + CO2

CH4 + O2 H2O + CO2

Combustion

…Switch out ONE element with another!...

GH + I GI + H

CuCl2 + Zn ZnCl2 + Cu

Single Replacement

…Switch Out Two Elements with Two Others!...

JK + LM JM + KL

AgNO3 + HCl AgCl + HNO3

(Stop Here)

Double Replacement

ConcentrationHigh Concentration = faster reaction

Surface AreaMore surfaces available to react = faster reaction

TemperatureHigher Temperatures = faster reaction

Particles speed up or slow down…speeding up or slowing down the reaction…

Rate of Reaction

CatalystSomething that speeds up the rate of reaction

without being affected itself.

InhibitorSomething that slows down the rate of

reaction without being affected itself.

(Stop Here)

Rate of Reaction (Cont’d)

Matter Can Neither Be Created Nor Destroyed

Reactants and Products MUST be EQUAL!

So…

We Balance Chemical Equations!

The Law of Conservation of Mass

Adding Coefficients to Reactants and Products in order to make both sides of the arrow EQUAL!

Na + Cl2 NaCl

Reactants Yields Products

This Chemical Equation is WRONG! (Why??)Na: 1 Na: 1

Cl: 2 Cl: 1The Numbers of Atoms are not BALANCED!

Balancing Equations

So….We add Coefficients to Make the Equation Balanced! We can NEVER EVER Add or Take

Away Subscripts! EVER!!

Na + Cl2 NaClNa: 1 Na: 1Cl: 2 Cl: 1

It is BALANCED!! WOO HOO!

Balancing Equations (cont’d)

So…My Balanced, Correct Chemical Reaction Between Sodium and Chlorine

is…

2Na + Cl2 2NaCl

This says that TWO atoms of sodium react with ONE diatomic molecule of

chlorine and produces TWO molecules of sodium chloride!

Balancing Equations (Cont’d)

H2 + O2 H2O

H: H:O: O:

Balancing: Your Turn

Start By Setting it Up Like This

H2 + O2 H2O

H: 2 H: 2O: 2 O: 1

Answer!

¿¿¿ ¿¿¿Questions ??? ???

Try to balance the following reactions! You may check with a partner as you work!

1. Mg + O2 MgO

2. N2 + H2 NH3

3. Cl2 + KI KCl + I2

4. Na + HCl H2 + NaCl

Balancing Practice

1. 2Mg + O2 2MgO

2. N2 + 3H2 2NH3

3. Cl2 + 2KI 2KCl + I2

4. 2Na + 2HCl H2 + 2NaCl

Balancing Practice – Answers!

Copy and complete the following flow map using your notes. Be sure to COLOR CODE to match your notes! Add extra reminder “bubbles” as you go!

How to Balance Chemical Equations

INB 93

1) Count the number of ATOMS on each side of the chemical

equationH2 + O2 H2O

H: 2 H: 2 O: 2 O: 1

2. Add Coefficients on each side of the equation so that…

3. …Continue…

Classifications 1 (1:30)Classifications 2 (1:30)

Alkali Metals in Water (3 min)Sodium in Water (1 min)Dry Ice Eruptions (11 min)Francium Bomb in Ocean (30 sec)Chemistry Explosions (13 min)

Videos!