Acids%20and%20Bases

1
Acids and Bases

• And Neutralisation Reactions p. 80-82

2
What are acids?

• Working together with your bench group using
  the information in your text book (Ch 4 p 80),
• expand this Mind Map

Acids
eg
Have a sour taste
Are used for
3
What are bases?

• Working together with your bench group, expand
  this Mind Map

bases
eg
Have a bitter taste (think of baking soda!)
Are used for
4
Experiment 13 Testing for Acids and Bases

• Aims
• to determine which substances are acids and bases
  using universal indicator
• to compare the colour produced using plant
  indicators with those produced using universal
  indicator

5
Materials

• Glass plate with wells
• Droppers
• Universal indicator
• Colour chart
• Red Cabbage Indicator
• Hydrochloric acid (HCl)
• Sodium Hydroxide (NaOH)
• Vinegar
• Lemon Juice
• Sodium bicarbonate (NaHCO3)
• Water (from tap)
• Other Substances as supplied

6
Method

• Collect the substances listed above and place
  about 0.5 ml in separate wells on the glass
  plate, as shown.
• Use a new well for each substance.
• Add two drops of Universal indicator to each well
  
• Record the colour that the indicator became
• Use the glass test plate outline supplied to
  estimate the pH and record this also.
• Test these substances with Red Cabbage Indicator
  and record the colours on a new sheet
• Hydrochloric acid (HCl)
• Sodium Hydroxide (NaOH)
• Vinegar
• Lemon Juice
• Sodium bicarbonate (NaHCO3)
• Water (from tap)
• Copy the table on the next slide into your
  workbook
• Safety Issues?

7
Comparing Indicators
Substance tested Colour with Universal Indicator pH as read from Chart Colour with Red Cabbage Indicator
Hydrochloric acid
Sodium hydroxide
Vinegar
Lemon juice
Sodium bicarbonate solution
Tap water
8
Neutralisation Reactions

• Acids and bases react together! (Remember the
  vinegar and Bicarb?)
• The general overall word equation is
• Acid Base? a Salt water
• Except if you use a bicarbonate or carbonate
  (which are bases) and then its
• Acid bicarbonate/carbonate ? a Salt water
  carbon dioxide

9
Try This!

1. Put a small amount of vinegar 2 drops only of
   indicator in a test tube
2. Add 0.1 M NaOH drop by drop
3. Can you get the pH to be just 7?

10
Activities

• On the Intranet in the Acids and Bases Section
  try
• GEMS Alien Juice Bar
• Treasure Puzzle