Name______

Acids and Bases: The pH of Foods

INTRODUCTION

The pH of certain foods is important for several reasons. How acidic or basic food is influences its taste. Acidic pH tends to prevent foods from spoilage. It also often imparts a tart flavor. Highly acidic or basic pH can also result in the destruction of some vitamins and nutrients within foods, while it will preserve others. Measured pH indicates the level of ripeness (or over-ripeness) of many fruits, especially citrus fruits.

PROCEDURE

  1. Working with your lab group, predict whether you think each of the food products in the DATA TABLE is either and acid (A), base (B) or neutral (N) before you begin the test. (Hint: What do acids and bases taste like?)
  1. Then, use pH paper to determine the pH of the different solutions of food products. You do this by dipping the paper into a small amount of the solution or placing it into the juice of a food and comparing the final color of the paper to a pH key. Record your results on the data table.
  1. After testing all the solutions, mark whether or not they are truly acidic, basic or neutral in the last column of the data table.

Acid pH levels: 0-6

Neutral pH level: 7

Base pH levels: 8-14

QUESTIONS

  1. Which solutions were acidic? Which of your predictions of acidic foods were wrong?
  1. Which solutions were basic? Which of your predictions of basic foods were wrong?
  1. Which solutions were neutral? Which of your predictions of neutral foods were wrong?
  1. Do you think all tap water has the same pH? Why or why not?

DATA TABLE
Prediction: Acid, Base, or Neutral / Solution / pH / Results: Acid, Base, or Neutral
(1) Tap Water
(2) Distilled Water
(3) Vinegar
(4) Baking Soda (NaHCO3)
(5) Egg Whites
(6) Corn Syrup
(7) Lemon Juice
(8) Sour Cream
(9) Coke (Pepsi)
(10) Tabasco Sauce
(11) Salt Solution
(12) Vanilla
(13) Sugar Solution
(14) Tums
(15) Milk
(16) Ranch Dressing
(17) Vanilla Flavoring
(18) Hot Chocolate
(19) Teacher Made Solution A
(20) Teacher Made Solution B