1. Module 5 Intro

1.30. Lesson 5 Intro

Lesson 5

Module 5—Acids and Bases

Lesson 5—Indicators

 

Get Focused

 

A photograph shows two cups of tea, a teapot, a sugar bowl, and a bottle of lemon juice. The colour of the tea inside the cup beside the lemon juice appears light brown. The colour of tea inside the other cup is a very dark brown-black in colour.

The last few weeks have been really busy, so now it’s time to reconnect with your friends. One way to catch up with friends is to meet and talk while enjoying a cup of tea.

 

Many people like to add things to their tea, but have you ever considered that a chemical change could result? Lemon juice is a popular thing to add to tea. Lemon juice contains citric acid and other weak acids. In this module you have learned that acids can give food a sour taste.

 

The cup of tea on the left has a teaspoon of lemon juice. What changes do you observe to the tea inside the cup? You may recall from previous science courses that colour change is one evidence of a chemical reaction. But what component of tea is involved in the reaction and how is lemon juice involved? You may also recall other foods that change colour when exposed to acids or bases.

 

In this lesson you will study the group of molecules called pH indicators. You will examine how the colour changes that indicators undergo are an example of an acid-base reaction. You will also discover how these compounds can be used to estimate the pH of other solutions.

 

Essential Questions
  • What are acid-base indicators?
  • How are acid-base indicators used to predict the pH of a solution?
Module 5: Lesson 5 Assignment

 

Save a copy of the Module 5: Lesson 5 Assignment to your course folder. Later in the lesson you will receive more information about how to complete this assignment and when to submit it to your teacher.

 

You will also conduct research to identify other substances that could act as pH indicators and design an experiment to test their properties.

 

You must decide what to do with the questions that are not marked by the teacher.

 

Remember that these questions provide you with the practice and feedback that you need to successfully complete this course. You should respond to all the questions and place those answers in your course folder.