Getting Down to Basics (and Acidics)
Return to Chemistry Index
Deborah Lewis Hinton School
644 West 71St. Street
Chicago, Il. 60621
Grade level 7th
1. Students will identify and define the concepts of acid, base, indicator and
2. Students will identify, classify and observe common household substances as
an acid, a base or neither.
3. Students will record all observations and findings in a data table.
dilute hydrochloric acid bleach orange juice
dilute sodium hydroxide solution soda water scouring powder
red litmus paper corn syrup tea
blue litmus paper limewater baking soda
beakers or small glass jars alcohol milk
household ammonia table salt lemon juice
milk of magnesia detergent seltzer tablet
goggles labels phenolphthalein
The words acid, base, indicator and neutralization will be developed. Teacher
will pass out to students pieces of lemons. Students will use their sense of
taste and taste the lemon. They will conclude that an acid is a chemical
compound that tastes sour. Next a bar of soap (which has been left in water)
will be, passed out to students (use sense of touch). One student will be
selected to sip some black coffee (sense of taste). They will conclude that a
base is a chemical compound which is slippery and taste bitter. For all
practical purposes you should never touch or taste an acid or base. Acids and
bases, which are strong, can be poisonous and corrosive to skin. To taste or
touch are not safe methods to identify an acid or base.
Teacher will do a demonstration on "Turning Water to Wine" by the following
method: Place 20ml of a base into one beaker, and 20ml of an acid into a second
beaker. Pour water that contains phenolphthalein, a colorless indicator into
the first beaker. The water appears to change into a red wine (or pink). Pour
red solution into the second beaker and it appears to turn back into water. Do
not discuss at this point.
Students will be asked a question. Suppose you are driving a car and your gas
is low. When the needle reaches past the red mark, what happens? (low fuel)
What is the device called that monitors the low fuel? (low fuel indicator
light) From the demonstration and the question, students should elicit the
definition of indicator as a substance that changes colors when acids and bases
are present. That neutralization is when an acid and base combine, they react
in a neutralization reaction. The products of a neutralization reactions are
water and salt.
1. Put a small amount of dilute hydrochloric acid in one beaker and a small
amount of sodium hydroxide solution, a base, in another. CAUTION: use care in
handling acids and bases.
2. Dip a piece of red litmus and blue litmus paper into each beaker. Observe
which piece of litmus paper changes color in each liquid. Record your
Use your observations to answer the following questions.
1. Which piece of litmus paper change color in the dilute hydrochloric acid?
2. Which piece of litmus paper changed color in the dilute sodium hydroxide
3. How can red litmus paper and blue litmus paper be used to tell whether a
substance is an acid, a base, neither?
Directions: In this part of the activity you will test some common household
substances to find out if they are acids, bases, or neither. You may share the
materials with other students' but you should make and record your own
1. Put small amounts of the substances to be tested in small beakers. Add water
to the beakers containing solid substances. Label each beaker with the name of
the substance it contains.
2. Dip a piece of red litmus paper and a piece of blue litmus paper into each
substance. Those substances that change the color of the litmus the way
hydrochloric acid does are acids. Those that change the color of the litmus
paper the way the sodium hydroxide does are bases. Those that do not change
the color of either red or blue litmus paper are neither acids nor bases.
Record your observations in the table.
Use your data and observations to answer the following questions
1. Which of the substances that you tested caused blue litmus paper to turn
2. To what class of compounds do the substances that caused the paper to turn
red belong? How do you know?
3. Which substances that you tested caused red litmus paper to turn blue?
4. To what class of compounds do the substances that caused the paper to turn
blue belong? How do you know?
5. Which of the substances that you tested did not change the color of either
blue litmus paper?
6. To what class or classes of compounds might those substances that did not
change the color of either red or blue litmus paper belong?
7. How do the results of this activity compare with your expected outcome?