Observations

Scientists are problem solvers, and one of the most important ways they gain information they need to solve problems is by making detailed and accurate observations. Observations are one of the key processes in experiments. This experiment is an example of problem solving by using observations.

When substances are mixed together, one of two things can happen. The first is that no change occurs. The substances are stirred together but remain the same substances. The second is that a change occurs. The substances interact in some way that results in the formation of different substances.

In this experiment, you will observe the interaction brought about when eight known substances are combined in different ways.

You will write a hypothesis for this lab.

You will observe the results of mixing eight different substances.

You will record your observations.

You will following your safety guidelines—googles, apron, closed-toed shoes, hair out of your eyes, remember that all substances are always treated as hazardous, and you will clean up any spills and at the end of class. Remember to report any spills or accidents.

You will use the following materials—

Microplate Data Form

Plastic wrap

Microtip pipets

Beaker (any size)—for water

Toothpicks for each well used

You will use the 8 solutions listed below—

A Nitric Acid 1

B Silver Nitrate 2

C Sodium Iodide 3

D Lead(II) Nitrate 4

E Sodium Carbonate 5

F Iron(III) Nitrate 6

G Sodium Hydroxide 7

H Copper(II) Nitrate 8

Procedures you will need to following—

  1. Label your Microplate Data Forms (3 for each group).

Place the Data Form on the counter numbered columns at the top and lettered rows on the left.

  1. Label the rows and columns with the names of the substances—make sure you write the names in the margins, not in the blocks.
  2. Example—beside A write nitric acid, B write silver nitrate, C write sodium iodide, continue through H.
  3. Example—above 1 write nitric acid, 2 write silver nitrate, 3 write sodium iodide, continue through 8.
  4. We will save time and chemicals by only mixing chemicals with each other one time and we will not mix chemicals with themselves. We will place X’s in squares to avoid double mixing.
  5. Tape one of the labeled microplates to your lab counter and cover with plastic wrap, making sure you tape the plastic wrap so you do not have wrinkles in it.
  6. The labels on your data form show the solutions to be mixed in each square. Make sure you get the right chemicals—read the names carefully.
  7. Put a beaker of water on the counter. Each person in the group needs a microtip pipette.
  8. Carefully wipe the plastic wrap with a paper towel, hopefully this will prevent movement of the liquids.
  9. Using a clean microtip pipette place 3 drops of the substance you assigned to row B onto the plastic wrap over each square without an X. If you have any excess chemical, discard it in the sink.
  10. Clean the pipet by pulling water into it (water in your beaker) discard in the sink and repeat three times.
  11. Using a clean pipette place 3 drops of the substance you assigned to row C onto the plastic wrap over each square without an X. If you have excess chemical, discard it in the sink.
  12. Follow the same procedure for row D.
  13. Using a clean microtip pipette add 3 drops of the solution you assigned to column 1 to every square in column 1 without an X.
  14. Remember to clean your pipette, repeat step 14 with substances 2-8.
  15. Stir each set of chemicals with a different toothpick.
  16. Examine each square. Record your observations on your microplate data form. If nothing happened write NR in the square.
  17. Once you have mixed the substances A-D and 1-8 and have written all your observations—wipe the chemicals off the plastic wrap with a paper towel. Discard the paper towel in a trash can.
  18. Now repeat steps 10-18 for the rows E-H and 1-8. Use fresh water and remember to clean your pipettes between chemicals.
  19. Record all your observations on your microplate data form.
  20. Discard the plastic wrap in the trash can and remove your data form.
  21. Put away all your equipment. Wash your hands and googles, then remove your apron. Place all your equipment in your Chemistry Locker.

You will have all of your observations listed in the squares of your data form.

You will have a hypothesis for this lab.

You will need to answer the following question: What are three different types of changes you observed during this lab?