1. Types of Reactions

2. Recall A + B  C + D A and B are called reactants Means ‘yields’
C and D are called products

3. Evidence of chemical reactions
At least one of these should be obvious when a chemical reaction takes place:
Color change - new substances might reflect different colors of light.
Heat change - the container may get hotter or colder.
Gas produced - bubbles or smoke may be observed.
Precipitate formed - an insoluble solid might form in a liquid.

4. Types of reactions: Synthesis – to build up
Decomposition – to break down
Single displacement – to replace one thing
Double displacement–to replace two things
Combustion – burn in presence of oxygen

5. Synthesis
This reaction involves the combination of smaller atoms and/or molecules to produce a single product.
Hydrogen chloride and ammonia yield ammonium chloride
HCl + NH3  NH4Cl

6. Decomposition
This reaction involves the splitting of a large molecule into elements or smaller molecules.
Sodium iodide  sodium and iodine
2NaI  2Na + I2

7. Single Displacement
This chemical change involves an element and a compound as reactants. One element will DISPLACE the element from the compound.
Mg + Ag(NO3)  Ag + Mg(NO3)2

8. Double Displacement
This reaction occurs when elements in different compounds displace each other or exchange places.
Pb(NO3)2 + KI  PbI2 + K(NO3)

9. Acid + Base  salt + water
Double Displacement
Neutralization of an acid and a base is also an example of a double displacement reaction.
Acid + Base  salt + water
Ex.
HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l)

10. Combustion
This is generally a very quick reaction where one reactant is oxygen and the product formed is an oxide.
Mg + O2  MgO
C4H10 + O2  CO2 + H20 (complete combustion)
Incomplete combustion forms CO2, CO, C and H2O

11. Metal oxides Mg + O2  MgO(s) MgO(s) + H2O(l)  Mg(OH)2(aq)
pH scale measure the amount of hydrogen ions in the solution.
pH scale:
0 (very acidic) 7(neutral) 14 (very basic)

12. Indicators to measure pH
Litmus paper
Red litmus turns blue in a base
Blue litmus turns red in an acid
BTB(bromothymol blue)
Turns blue in a base
Turns yellow in an acid
Turns green in a neutral solution
PHTH (phenophthalein)
Turns colourless in an acid
Turns magenta pink in a base

13. Non-metal oxide Non-metal oxide and water form an acid.
CO2 + H2O(l)  H2CO3(aq)
Therefore this would lie under 7 on the pH scale (acidic environment)