Name:
Class:
Date:
Chapter 8:
Acids and Alkalis
Activity 8.1
Properties of Dilute Acids
Suggested
duration
Aims
2 periods
70 minutes
• To investigate the effect of acids on litmus paper and taste of organic acids
• To investigate the taste of organic acids
Skills
You will learn to:
• identify the properties of acids
• show an awareness of the presence of acids in our daily lives
Apparatus and Materials
• a white tile
• small limes (cut in half)/
a slice of lemon (for tasting)
• lime/lemon juice in bottle
• red and blue litmus papers
• two strips of filter paper
• a dropper
•
•
•
•
•
•
ethanoic acid (vinegar)
dilute hydrochloric acid
dilute sulphuric acid
dilute nitric acid
ethanoic acid (vinegar)
at teacher’s bench (for tasting)
Procedure and Observations
1.
Rinse the white tile with tap water.
2.
Place one strip of red litmus and one strip of blue litmus paper side by side on the
white tile.
3.
Using the dropper provided, place two drops of hydrochloric acid onto each piece
of litmus paper.
4.
Record the changes in colour in the table provided.
5.
Rinse the dropper and white tile thoroughly.
6.
Repeat steps 1 to 5 for each acid provided.
dilute
hydrochloric
acid
dilute
sulphuric
acid
dilute
nitric
acid
ethanoic
acid
© 2008 Marshall Cavendish International (Singapore) Pte Ltd
LSSPB_vA_08cos.indd 85
lemon/
lime
juice
Acids and Alkalis
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7/31/07 4:27:20 PM
Acid
Dilute hydrochloric acid
Dilute sulphuric acid
Dilute nitric acid
Ethanoic acid (vinegar)
Lime/lemon juice
Effect on blue
litmus paper
Effect on red
litmus paper
Turns red
Remains red
Turns red
Remains red
Turns red
Remains red
Turns red
Remains red
Turns red
Remains red
7.
Squeeze a few drops of lime/lemon juice onto a clean piece of filter paper. Place the
filter paper at the tip of your tongue. Rinse your mouth and record the taste of the
lime/lemon juice in the table provided.
8.
Dip another clean piece of filter paper into the ethanoic acid (vinegar) found at your
teacher’s table. Taste the acid and record your observation.
Acid
Lime/lemon juice
Ethanoic acid (vinegar)
Taste
sour
sour
Note
Never taste any chemicals in the laboratory without your teacher’s instructions.
9.
What can you conclude about the properties of acids?
Acids are
sour
and they turn blue litmus paper
red
.
Discussion
1.
a)
How can you conclude that limes/lemons contain an acid?
They taste sour and turn blue litmus paper red.
b)
What acid is found in limes and lemons?
Citric acid.
2.
Can we test for an acid by tasting them? Why?
No. Common dilute acids are corrosive and cause burns.
3.
What acid is found in our stomach? What causes “heartburn”? (You may need to do
some research.)
Hydrochloric acid. Heartburn is caused by a special type of indigestion where acid from the stomach is
regurgitated upwards into the food pipe or oesophagus.
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Acids and Alkalis
© 2008 Marshall Cavendish International (Singapore) Pte Ltd
7/31/07 4:27:22 PM