Student Portal:

Acids and Bases

Investigation 1 – Lab

 

 

 

 

 

 

 

MINDSET

This Investigation is designed to:

  • allow you to recognize some acids and bases as common and familiar household chemicals,
  • allow you to realize that acids and bases are not necessarily strong or dangerous,
  • enable you to become proficient at measuring pH,
  • allow you to measure the pH of different chemical compounds,
  • promote your categorization of different chemical compounds as acids or bases, and
  • allow you to correlate the differences among acids and bases with the differences in hydrogen ion concentration of solutions of the two classes of compounds.

BE PREPARED

Student Preparation for the Investigation includes having students gather the following materials. This preparation takes place on lab day after student lab groups have settled at their assigned lab tables.

Note: The materials are listed in your SDR. They are also listed below for your reference.

  • (1) pair of goggles per student
  • (1) pair of gloves per student
  • (1) test tube rack
  • (8) 15 ml centrifuge tubes
  • (8) dropper pipettes
  • (1) box of pH paper strips
  • (1) pair of forceps
  • 5 ml acetic acid solution (vinegar)
  • 5 ml sulfuric acid solution (automobile battery acid)
  • 5 ml hydrochloric acid solution (stomach acid)
  • 5 ml citric acid solution (lemon juice)
  • 5 ml carbonic acid solution (carbonated soft drink)
  • 5 ml sodium hydroxide solution (drain cleaner)
  • 5 ml ammonium hydroxide solution (window cleaner)
  • 5 ml magnesium hydroxide solution (liquid antacid medication)

Direct one student from each lab group to collect the materials listed in their SDRs.

INVESTIGATE

  • You will perform two Trials during this Investigation. Trial 1 introduces acids and Trial 2 introduces bases.
  • Data for Trial 1 should be recorded in Table A and data for Trial 2 should be recorded in Table B in your SDR.
  • As each Trial is completed, you should answer the questions at the end of each Trial.
  • Reflect on the PreLab video as you move through the procedural steps.
  • During the Experiment, every procedural step is important. If one step is skipped, data can become invalid. To help you keep on track, read each step thoroughly, complete the step, then check it off (Read it – Do it – Check it).
  • Complete all of the procedural steps in your SDR.

Note: The procedural steps are listed below for your reference.

 Trial 1:

  1. In this Trial, you will determine the pH of several different solutions that contain acids. Review the Procedure, Determination of pH.
  2. Using the lab marker and the masking tape, label a centrifuge tube with the names of each solution listed in Table A. Using a dropper pipette, add 5 ml of each solution to a centrifuge tube.
  3. Using forceps grasp the top of a pH paper strip and dip ¼ of the strip into the vinegar. Remove the pH paper strip.
  4. Match the color on the strip with the pictures of the squares on the pH chart. Estimate the pH of the vinegar that most closely corresponds to the color of the colored squares in the pictures. Estimate the pH to the nearest half of a pH unit, for example, 3.0, 3.5, or 4.0. Record the pH value in Table A.
  5. Repeat steps 1 through 3 for each of the other acids.

 

 

  1. Which of the acids that were tested are familiar to you? 
  2. Using the data from Table A, write the names of the acids in order from lowest to highest pH. Use the pH Scale from the Background. 
  3. What does the order of the acids tell you about the concentration of H+ ions in each solution of acid? 
  4. Which atom is present in the chemical formula of each acid? 

Trial 2:

  1. In this Trial, you will determine the pH of several different solutions that contain bases.
  2. Label a centrifuge tube with the names of each solution listed in Table B. Using a dropper pipette, add 5 ml of each solution to a centrifuge tube.
  3. Using forceps grasp the top of a pH paper strip and dip ¼ of the strip in the drain cleaner. Remove the pH paper strip.
  4. Match the color on the strip with the pictures of the squares on the pH chart. Estimate the pH of the drain cleaner that most closely corresponds to the color of the colored squares in the pictures. Estimate the pH to the nearest half of a pH unit, for example, 3.0, 3.5, or 4.0. Record the pH value in Table B.
  5. Repeat steps 1 through 3 for each of the other bases.

 

 

 

  1. Which of the bases that were tested are familiar to you? 
  2. Write the names of the bases in order from lowest to highest pH. Use the pH Scale from the Background. 
  3. What does the order of the bases tell you about the concentration of H+ ions in each solution of base?
  4. Which two elements are present in the chemical formula of each base? 

CLEAN UP

Be sure to clean up your lab bench after finishing your experiments.