Contributed by: The RAND Institute (RAND)
Acids and Bases Alien - Form R
Task: In this activity you will be working by yourself.
You can write your answers directly on these pages. If you have
a question, please raise your hand and we will come to help you.
Please take the materials out of the bag in front of you. Put
the materials on your placemat. Raise your hand if you are missing
any of these materials:
Materials:
- 1 bag pH indicator paper strips
- 1 pH Color Chart
- 8 plastic measuring cups
- 1 dropper bottle Solution X
- 1 dropper bottle Alien Blood
- 1 dropper bottle Medicine A
- 1 dropper bottle Medicine B
- 1 dropper bottle Medicine C
All solutions are acids, bases, or neutral. You can use pH paper
and a pH Color Chart to test whether a solution is an acid, a base,
or neutral.
Part 1: READING THE pH SCALE
To practice using the pH paper:
- Squeeze 6 drops of Solution X into one of the measuring cups.
Gently swirl the cup.
- Take one strip of pH paper out of the bag, and dip it into Solution
X.
- Remove the strip from the cup and quickly observe the
color of the pH paper. Be sure to look at the color right away,
because it will change quickly. The first color shows the correct
pH.
1a. What is the color of the pH paper right after you dipped
it into solution X? _____________
1b. What number on the pH color chart goes with this color?
_____________
1c. Look at the chart below. Is solution X an acid, a base, or
neutral? _____________

Part 2: THE PROBLEM
You are an expert in blood chemistry. The blood of an alien creature
is brought to your laboratory for analysis. The alien has a sever
headache and a high temperature. The doctors say the alien has a
sickness called acidosis-basicosis. This condition is caused by
the blood being either too acidic (low pH) or too basic (high pH).
The normal pH for alien blood is 7.0. The alien will die if its
blood stays away from 7.0 for more than a few hours.
To find out what is wrong with the alien, test the pH of its blood
to see if it is too acidic or too basic.
- Squeeze 6 drops of the alien's blood into a new measuring cup.
- Test the pH of the alien's blood using a new strip of pH paper
and the color chart.
2a. What was the color of the pH paper right after you took
it out of the alien's blood? __________
2b. What number on the pH color chart goes with this color?
___________
2c. The alien is suffering from acidosis/basicosis because its
blood is (circle the right choice):
- Too acidic
- Too basic
- Too neutral
Part 3: FINDING THE BEST MEDICINE
The alien's spaceship has a first aid kit with three medicines.
One or more of these medicines can cure acidosis/basicosis when
it is added to the alien's blood.
Your job is to figure out which medicine ( A, B, or C) will save
the alien's life by bringing the pH of its blood back to normal.
You will do this in two stages. In Stage I, you will test the pH
of each medicine. In Stage II, you will test what happens when you
combine the alien's blood with each medicine.
Follow the steps below and record the results of your experiment
in Table 1 as you work.
Stage I - Testing the Medicines
- To test Medicine A:
- Record your results in Table 1, making sure that you describe
both the color of the pH paper and its pH number.
- Repeat steps 1 and 2 for Medicine B with a new cup and
new pH strip.
- Repeat steps 1 and 2 for Medicine C with a new cup and
new pH strip.
Stage II - Testing Mixtures
- Fill a new cup up to the 5ml level with alien blood.
- Add 3 drops of Medicine A to the cup, gently swirl the cup,
dip a new piece of pH paper into the solution, and quickly
match the color on the pH paper with the Color Chart.
- Record the color of the pH paper and the pH number in Table
1.
- Add 3 more drops of Medicine A to the cup, gently swirl the
cup, dip a new piece of pH paper into the solution, and
quickly match the color on the pH paper with the Color Chart.
- Record the color of the pH paper and the pH number in Table
1.
- Repeat steps 5-9 using Medicine B.
- Repeat steps 5-9 using Medicine C.
Table 1
Solution Tested |
Color |
pH Number |
3 drops Medicine A |
|
|
3 drops Medicine B |
|
|
3 drops Medicine C |
|
|
5ml blood + 3 drops Medicine A |
|
|
5ml blood + 6 drops Medicine A |
|
|
5ml blood + 3 drops Medicine B |
|
|
5ml blood + 6 drops Medicine B |
|
|
5ml blood + 3 drops Medicine C |
|
|
5ml blood + 6 drops Medicine C |
|
|
Part 4: DRAWING CONCLUSIONS
Use the results of your experiment to answer the following questions:
4a. Which is the best medicine (A, B, or C) for the alien? ______________
4b. Why is this medicine better than the other medicines? (You
may use a table, graph, or picture to help you explain your answer).
4c. How can a basic solution be turned into a neutral solution?
4d. How can an acidic solution be turned into a neutral solution?
Part 5: USING WHAT YOU LEARNED
The people of Spring City were concerned because the fish in their
pond were dying. They hired an environmental scientist who measured
the pond's pH and found that it was too acidic. Pond fish need neutral
water to survive. The people followed the specialist's advice and
added Pro-Base, (a strong base) to the pond. After two days, the
fish stopped dying. The people kept adding Pro-Base to the water
and after three more days, the fish started dying again. In fact,
the more Pro-Base they added, the more fish died.
5a. Why did Pro-Base work at first, but not continue to work?
5b. What should the people in Spring City do now to save the fish
in their pond? (Circle the best choice)
- Add no more chemicals
- Add an acidic substance
- Add a neutral substance
- Add more Pro-Base
5c. Why did you choose this answer?
|