Chemical Reactions

? Chemical Reactions

? Observing Chemical Reactions

Evidence:1) The colour changes2) Bubbles A gas is produced3) The mixture gets hotter (EXOTHERMIC)or colder (ENDOTHERMIC) 4) A solid (PRECIPITATE) forms from two

aqueous solutions

? Observing Chemical Reactions

Evidence:1) The colour changes2) Bubbles A gas is produced3) The mixture gets hotter (EXOTHERMIC)or colder (ENDOTHERMIC) 4) A solid (PRECIPITATE) forms from two aqueous solutions

Dissolved in water

? Demo’s

What evidence is there that a chemical reaction has occurred?

? Representing Chemical Reactions

In a chemical reaction, one or more substances change to produce new substances.

 • The starting materials are called REACTANTS and the

materials you finish with are called the PRODUCTS. • A plus + sign is used between a list of different

reactants and products. • An arrow is used between the reactants and products

to show that the reactants get turned into the products.

? Word Equations

A word equation describes a chemical reaction using the names of the reactants and products.

Examples: Hydrogen + Oxygen water Acetylene + oxygen carbon dioxide + water

? Word Equations

A word equation describes a chemical reaction using the names of the reactants and products.

Examples: Hydrogen + Oxygen water 

Acetylene + oxygen carbon dioxide + water

Reactants

Reactants

Products

Products

? Practice

Write word equations for the following descriptions. Underline the Reactants and Circle the Products in each.

1) Aluminum metal combines with chlorine gas to make aluminum chloride.

? Practice

Write word equations for the following descriptions. Underline the Reactants and Circle the Products in each.

1) Aluminum metal combines with chlorine gas to make aluminum chloride.

aluminum + chlorine aluminum chloride  

? Practice

Write word equations for the following descriptions. Underline the Reactants and Circle the Products in each.

  2) Magnesium metal combines with nitrogen gas to make magnesium

nitride.

? Practice

Write word equations for the following descriptions. Underline the Reactants and Circle the Products in each.

  2) Magnesium metal combines with nitrogen gas to make magnesium

nitride.

magnesium + nitrogen magnesium nitride 

? Practice

Write word equations for the following descriptions. Underline the Reactants and Circle the Products in each.

3) Calcium chloride and sodium sulfide solutions are mixed. A precipitate of calcium sulfide and sodium chloride solution is made.

? Practice

Write word equations for the following descriptions. Underline the Reactants and Circle the Products in each.

3) Calcium chloride and sodium sulfide solutions are mixed. A precipitate of calcium sulfide and sodium chloride solution is made.

Calcium chloride + sodium sulfide calcium sulfide + sodium chloride  

? Chemical Equations

A chemical equation is a short hand way of representing a chemical change in which chemical formulas are used for the reactants and products.

? States for Substances

The states for the substances may be included using the following symbols:

State Symbol Meaning(s) Solid

(l) liquid

(g) gas

(aq) aqueous

? Examples

H2 (g) + O2 (g) H2O (l)

C2H2 (g)+ O2 (g) CO2 (g) + H2O (l)

? Reminders

• Don’t forget the diatomic elements: Hydrogen H2 Fluorine F2 Oxygen O2 Chlorine Cl2Nitrogen N2 Bromine Br2

Iodine I2

  Don’t forget to criss-cross the numbers in the ions to

make the subscripts in the compounds. 

? Examples

Translate the following word equations into chemical equations:

1) sodium + chlorine sodium chloride   

? Examples

Translate the following word equations into chemical equations:

1) sodium + chlorine sodium chlorideNa+ Cl-

diatomic

? Examples

Translate the following word equations into chemical equations:

1) sodium + chlorine sodium chlorideNa+ Cl-

Na + Cl2 NaCl   

diatomic

? Examples

Translate the following word equations into chemical equations:

2) fluorine + calcium bromide bromine + calcium fluoride 

? Examples

Translate the following word equations into chemical equations:

2) fluorine + calcium bromide bromine + calcium fluoride  diatomic diatomic

? Examples

Translate the following word equations into chemical equations:

2) fluorine + calcium bromide bromine + calcium fluoride  diatomic diatomic

Ca2+ Br- Ca2+ F-

? Examples

Translate the following word equations into chemical equations:

2) fluorine + calcium bromide bromine + calcium fluoride

F2 + CaBr2 Br2 + CaF2

diatomic diatomicCa2+ Br- Ca2+ F-

? Examples

Translate the following word equations into chemical equations:

3) barium sulfide + potassium iodide barium iodide + potassium sulfide 

? Examples

Translate the following word equations into chemical equations:

3) barium sulfide + potassium iodide barium iodide + potassium sulfide 

Ba2+ I-K+ I-Ba2+ S2- K+ S2-

? Examples

Translate the following word equations into chemical equations:

3) barium sulfide + potassium iodide barium iodide + potassium sulfide 

BaS + KI BaI2 + K2S

Ba2+ I-K+ I-Ba2+ S2- K+ S2-