Student Exploration: pH Analysis
Vocabulary: acid, acidic, alkaline, base, indicator, neutral, pH
Prior Knowledge Questions (Do these BEFORE using 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? __Sour.______________________________
B. What does it feel like if lemon juice gets in your eye? ___It stings/burns!______
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? ___Slippery.__________________________________
B. What does soap taste like? ___Bitter/No flavor.___________________________
C. What does it feel like if soap gets in your eye? __Sting/Burns. It also makes your eyes water.__
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 excess 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 acids or bases. What is the color of the pH paper? __White.__
2. Compare the paper to the pH color chart. What is the pH of ammonia? ___11._______
3. Is ammonia acidic or alkaline? ___Alkaline._______
Get the Gizmo ready:
Check that the 0-14 paper is selected.
Goal: Find the pH of 18 common substances.
1. Test: Use the Gizmo to find the...
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