The pH Scale

Remember the household products lab? You tested household chemicals with litmus paper and pH paper. Product Color pH Formula Acid/Base? 1. 2. … 9.

What happened to the pH paper? pH paper (aka Universal Indicator Paper) What color(s) do/does the paper turn for acids? What color(s) do/does the paper turn for bases? Reds and oranges Greens and Blues

What is the pH scale? pH (“potential hydrogen”): another way of representing the hydrogen ion (H+) concentration of a solution pH values range from 0 - 14 BASIC ACIDIC

The pH scale Acidic solution: pH < 7.0 Neutral solution: pH = 7.0 Basic solution: pH > 7.0 Neutral ACIDIC BASIC pH = Increasing acidity Increasing basicity

The pH Scale

How can you tell the pH of a chemical? Indicators! Indicator paper (like pH paper) Liquid indicators (like phenolphthalein) pH meters

The pH range varies for different indicators Indicator: a chemical or solution that changes color at a certain pH The pH range varies for different indicators Titration Xample

Indicator Lab Instructions: Many naturally colored compounds can behave as acid-base indicators. In this lab, you will be given a choice of several different fruits and vegetables. Your goal is to make indicators from these fruits and vegetables. On lined notebook paper, you must do the following: Write a purpose. Provide a complete set of instructions for making the indicator solution from the raw materials and testing the solution. (The indicator is usually in the skin of the fruit or veggie. You will have to boil the fruit or veggie in a small amount of water to extract the indicator). Create a data table listing your results for 3 indicator solutions (see below). Answer the analysis questions. Available Materials: solutions with various pH, carrots, blueberries, red cabbage, red grapes, red onions, tea leaves, 100mL beaker, deionized water, pipettes, well plates, scoopula

DEMO Why do chemistry teachers like to teach about hydroxides?