Form T

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.

Part 1: READING THE pH SCALE

All solutions are acids, bases or neutrals. Chemists use pH paper and a pH Color Chart to test whether a solution is an acid, base, or neutral.

Anna is a chemist. Here are the materials she used to do some experiments.

In her first experiment, Anna tested Solution X:

• She put 6 drops of Solution X into one of the measuring cups.
• She dipped a strip of pH paper into the cup.
• She removed the pH strip from the cup and observed that it had turned orange.
• She looked at the pH Color Chart below to find the pH number that goes with orange.

1a. What is the pH number of Solution X? _____________

1b. Is Solution X an acid, a base, or neutral? ____________________

Part 2: THE PROBLEM

Anna is an expert in blood chemistry. The blood of an alien creature is brought to her 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, Anna tests the pH of its blood to see if it is too acidic or too basic.

• She puts 6 drops of the alien's blood into a measuring cup.
• She dips a strip of pH paper into the cup. The pH paper turns Green.

2a. What is the pH number for Green on the pH Color Chart? ____________

2b. This result means the alien is suffering from acidosis/basicosis because its blood is (circle the right choice):

1. Too acidic
2. Too basic
3. 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.

Anna's 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.

She does this by conducting an experiment in two stages. First she tests the pH of each medicine. She then tests what happens when she combines the alien's blood with each medicine.

1. To test Medicine A:
   
   
   
   
   
2. Because the strip turned Blue, Anna writes Blue and the pH number 11 in Table 1.
   
   
3. She tested Medicine B the same way and found that it turned the pH strip Yellow. What pH number goes with Medicine B? ___________ Put this number in the right place on Table 1.
   
   
4. She tested Medicine B the same way and found that it turned the pH strip Red. What pH number goes with Medicine C? ___________ Put this number in the right place on Table 1.
   
   
5. Anna now begins to test the pH of the alien's blood when she mixes it with a medicine.
   
   
6. Because the strip turns Green, Anna writes Green in Table 1. What pH number goes with Green? _____________ Put this number in Table 1.
   
   
7. Anna adds 3 more drops of Medicine A to the cup and dips a new piece of pH paper into it. The pH paper turns Green again.
   
   
8. Anna repeats steps 5-7 with Medicine B.
   
   
9. Anna repeats steps 5-7 with Medicine C.
   
   
10. Table 1 shows the color of the pH paper for each of Anna's tests. Your job is to finish the table by recording the pH number for each color.

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)

1. Add no more chemicals
2. Add an acidic substance
3. Add a neutral substance
4. Add more Pro-Base

5c. Why did you choose this answer?