ACIDS AND BASES

1
ACIDS AND BASES
2
Acids properties

• Conduct electricity (strong acids)
• Change blue litmus to red
• Have a sour taste
• React with bases to neutralize their properties
• React with active metals to liberate hydrogen
• pH values 6-0

3
Acids

• Acids are defined as
• Substances which ionize to form hydrogen() ions
  in aqueous solution. (Arrhenius)
• Substances that act as proton donors
  (Bronsted-Lowry) or as electron-pair acceptors
  (Lewis)
• Examples HCl, H2SO4

4
Bases properties

• Base properties
• Conduct electricity (strong bases)
• Change red litmus to blue
• Have a slippery feeling (like soap)
• React with acids to neutralize their properties
• pH values 8-14

5
Bases

• Bases are defined as
• Substances which ionize to form hydroxide ions
  OH(-) in aqueous solution
• Substances that act as proton receptors
  (Bronsted-Lowry) or as electron-pair donors
  (Lewis)
• Examples NH3OH, NaOH, CaCO3 , NaHCO3 (baking
  soda)

AMMONIAcleaner
6
pH Scale

• The pH scale is used to measure how acidic or
  basic is a liquid.
• pH measures the concentration of hydrogen ions
  (H) and hydroxide ions (OH-).
• The scale goes from 0 through 14. Distilled water
  is 7, so is called neutral.

7
Indicators

• An indicator is a large organic molecule that
  works somewhat like a "color dye."

8
Natural indicators

• There are natural indicators for acids and bases,
  and we may find them in our kitchen or garden!
• Red rose flowers
• Bougainvillea flowers
• Red cabbage
• Blue berries

http//tides.sfasu.edu2006/cdm4/item_viewer.php?C
ISOROOT/DigitalCISOPTR1019CISOBOX1REC4
9
Acids and bases reactions

• The acids react with bases, forming salts

ACID BASE ? SALT WATER HCl NaOH ? NaCl
H2O H-OH
10
Caves formation

• Cave formation is based on a chemical reaction
  between an acid and a base. This acid is
  carbonic acid (H2CO3), and the base is calcium
  carbonate (CaCO3), although it is not a direct
  reaction.

11
Caves formation

• Carbonic acid is formed by the reaction of rain
  water and carbon dioxide from soil. When the
  water is absorbed by the soil into the ground it
  reacts with the carbon dioxide present there
• H2O CO2 ? H2CO3
• Water carbon dioxide ?
  carbonic acid
• Carbonic acid is responsible for acid rain.

12
Caves formation

• The acid water reacts chemically with rocks made
  of the base calcium carbonate, called limestone,
  and dissolves them
• H2CO3 CaCO3 ? Ca H2CO3
• Carbonic acid calcium carbonate
  ? calcium carbonic acid

13
Caves formation

• The calcium reacts with the hydrogen carbonate
• Ca HCO3 ? CO2 CaCO3 H2O
• The carbon dioxide is given off into cave air to
  react again with rain water. Calcium carbonate is
  deposited, and water is formed. Thats the reason
  you will always see water inside the limestone
  caverns.

14
Caves formation

• These series of chemical reactions are very slow
  and take thousands of years to produce the
  characteristic stalagmites and stalactites of
  these caverns.

http//tides.sfasu.edu2006/cdm4/item_viewer.php?C
ISOROOT/PPYCISOPTR81CISOBOX1REC1
15
Resources
Animation of cave formation on Exploring
Earth http//www.classzone.com/books/earth_scienc
e/terc/content/visualizations/es1405/es1405page01.
cfm?chapter_novisualization