Summer Research Program for Science Teachers

 

Carla Brathwaite

Midwood High School

August 2005

 

 

Acidic Apples … Basic Belches

 

 

 

Unit – Acids and Bases

Time allotment:  At least 1 – 45 min period  (can be modified for a double period)

 

Objectives:  Students will be able to determine whether some common everyday consumables are acidic or basic.

 

** Previous day’s homework/extra credit – have students bring in the substances to be tested.

 

Materials:  pH probe and applicable software, phenolthalein, bromtymol blue, pH paper, red and blue litmus paper, methyl orange, 1M Hydrochloric acid, 1M Sodium hydroxide, burets, ring stands, clear cups/ 100 mL beakers, alcohol pads, squirt bottles with water (preferable deionized water),  Samples to be tested (Orange juice, Apple juice, milk, Maalox, tumbs, sink water, bottled water, coke, pepsi, sprite, liquid soap, cranberry juice, punch mix, lemonade, tea, laundry detergent, bleech, ammonia, baby oil, Milk of magnesia, soy sauce, etc) Preprinted data sheets for students to record observations (1 for each group or 1 per student)

 

Do now:    What is an acid?  What is a base?  List at least 3 things we use to determine whether a substance is an acid or base?  How do we determine the concentration of an unknown acid or base?  (Be sure students know the titration formula and how to use it)

 

Motivation:  What do you think heartburn is?  If you suddenly though you had heartburn and didn’t have any money or means of obtaining over the counter products designed to treat hearthburn what would you possibly use to treat your hearburn?

 

Procedure:

  1. Break the class up into groups of 3 or 4 students and position them in their groups throughout the room.
  2. Have 1 student from each group obtain 1 of each type of acid/base indicator
  3. Have another student from each group obtain a pH meter/probe
  4. Have another student from each group obtain a buret, ring stand and bottle of acid/base  (If there isn’t enough time students can do this the following day)
  5. Distribute data sheets to the students, assign group numbers
  6. Assign each group at least 3 – 4 substances that they should test for acidity or alkalinity (be sure to assign both acids and bases to each group)
    1. Students should at least use 3 different indicators
    2. All substances should be tested for pH
  7. Approximately 15 minutes before the end of the period stop all groups (students) from working.
  8. Assign each group 1 substance for them to titrate so that they can determine the molarity of the substance.  (You can assign 2 substances to titrate depending on how many substances you have throughout the room)
  9. If students work quickly enough, instruct them to titrate the substance twice and average the results of both trials
  10. At approximately 5 minutes to the end of the period, collect all materials.

 

Homework:

  1. Have students organize all their data for homework.  Should be easily readable, and ready to share with other students tomorrow.
  2. Have them look up what heartburn really is.  Then based on their data from class, which of the 3 – 4 substances they tested could be most efficient in treating heartburn and why?  Their reason should at least be 1 paragraph

 

Standards Addressed:

S4b – Demonstrates an understanding of the designed world

S4c – Demonstrates an understanding of health

S4e – Demonstrates an understanding of the impact of science

S5e – Works individually and in teams to collect and share information and ideas