Gizmo: pH Analysis
Vocabulary: acid, acidic, alkaline, base, indicator, neutral, pH
Prior Knowledge Questions (Answer these BEFORE beginning the Gizmo!)
1. Acids are substances that produce hydrogen ions (H+ ) when dissolved in water. Lemon juice
is an example of an acid.
A. What does lemon juice taste like? _____________________________________________
B. What would it feel like if lemon juice got in your eye? ______________________________
2. Bases are substances that produce hydroxide ions (OH- ) when dissolved in water. Hand soap
is an example of a base.
A. What does soap feel like? ___________________________________________________
B. What does soap taste like? __________________________________________________
C. What would it feel like if soap got in your eye? ___________________________________
Warm Up
The strength of an acid or base is measured on the pH scale. The term
“pH” is short for “potential of hydrogen.” It is a measure of how many extra
H+ ions there are in a solution. The pH scale runs from 0 to 14, with 0
representing the highest concentration of hydrogen ions. Acidic substances
have a pH below 7, while alkaline substances (bases) have a pH above 7.
Pure water has a pH of 7 and is considered neutral.
The pH Analysis Gizmo™ allows you to find the pH of a variety of liquids.
In the Gizmo, check that the Substance in the tube is Ammonia, and click
Test. Wait until the animation is finished.
1. Indicators change color in the presence of acids or bases. What
color is the pH paper? ___________________
2. Compare the paper to the pH color chart. What is the pH of ammonia? ___________________
3. Is ammonia acidic (an acid) or alkaline (a base)? ____________________________________
Measuring pH
Click Reset
Check that the 0-14 paper is selected
Goal: find the pH of 18 common substances
1. Test: Use the Gizmo to find the pH of each of the available substances. Write the name of
each substance, then classify each one as acidic (pH < 7), alkaline (pH > 7), or neutral (pH =
7). Record your data in the table in the 0-14 data table on ISN p. 55.
2. Test: Click Reset, then select the 4.5-7.5 paper. This paper can only measure pH values
between 4.5 and 7.5. First, record the pH values you just recorded in step 1 onto the 4.5-7.5
data table on ISN p. 55. Then, test each of those substances with the 4.5-7.5 paper and record
your new results.
p. 54
