New AACT Resources to Teach Acids-Base Concepts in AP Chemistry

In February 2016 I put together a list of AACT resources that could be used to teach acid-base titrations. Since then we have added over 100 new resources to our High School Resource Library and several of them could be used in an AP Chemistry class. The topic of titrations and buffer solutions is covered by several learning objectives in Big Ideas 1, 3, and 6. These new resources can help you prepare your students to meet these objectives.

Learning Objective 1.2 states: “The student can design, and/or interpret data from, an experiment that uses titration to determine the concentration of an analyte in a solution.”

Our Titration Curves lab allows students to generate and analyze titration data. Students complete four micro-scale titrations involving different combinations of strong and weak acids and bases. They then plot their data and graphically observe the curves determine the equivalence point of each plotted curve. By the end of this lab your students should be able to identify strong and weak acids and bases, identify the equivalent point of a titration reaction, and write a balance acid/base reaction. This lab supports students’ understanding of equivalence point, titrations, acid base reactions, and strong vs weak acids/bases. This is also an excellent activity for teachers who have limited supplies to use with their students.

It’s hard to design a titration without an understanding of how indicator solutions work.In the last year AACT has added four different classroom activities about indicators.

• Another Secret Message demonstration is a great way to introduce the concept of acid-base indicators. It allows students to observe a hidden message while understanding simple acid/base chemistry and indicators. By the end of this demo, students should be able to understand that an indicator causes a color change as the result of an acid-base reaction taking place.
• In our Milk of Magnesia Magic demonstration, students can observe a color change in a milk of magnesia solution as small amounts of vinegar are added and also see the effect of changing the temperature of the system. This demonstration supports students’ understanding of indicators, acid/base neutralization reactions, limiting reactants, Le Châtelier’s principle, and reaction rates.
• Your students can observe the color changes created by different indicators in our Indicators of Acids and Bases activity. In this lab, students use three indicators to identify unknown (clear) solutions as acidic, basic, or neutral. By the end of this lab, they should be able to explain that substances can be identified as acidic, basic, or neutral using indicators and identify the colors associated with a specific indicator when signifying either an acidic, basic, or neutral solution. This lab was created by a participant in the 2016 Dow and AACT Teacher Summit in Austin, TX.
• In the How to Perform a Titration demonstration you will show your students how a titration is set-up and performed. Additionally, you will use several different indicators to show how they work and why they are necessary. At the end of the demonstration you will discuss how to calculate the molarity of an unknown substance using data collected during the titration.

One of the most difficult concepts for AP Chemistry students to grasp is buffer solutions. This topic is covered by Learning Objectives 6.18 and 6.20. The second objective states: “The student can identify a solution as being a buffer solution and explain the buffer mechanism in terms of the reactions that would occur on addition of acid or base.” What are Buffers? activity can help your students meet that objective. In this activity, students complete a card sort that will allow them to understand what makes up a buffer solution and how it works to keep pH from changing.It includes identifying conjugate acid base pairs in a buffer solution and determining which species act as the acid and which acts as the base. Additionally, students must write the chemical reaction for the reaction of a strong acid and base with a buffer and then explain how the buffer is able to resist changes in pH. This activity was created by a participant in the 2016 Dow and AACT Teacher Summit in Austin, TX.

Another area of student confusion is determining the pH of a salt solution. The pH of Salts lab can help your students master this concept. In this lab, students determine whether an aqueous solution is acidic, basic, or neutral. They write net ionic equations for the hydrolysis of a solution. By the end of this lab, students should be able to predict the pH of a solution based on the formula of the salt and write equations for the hydrolysis of a salt. This lab was created by a participant in the 2016 Dow and AACT Teacher Summit in Austin, TX.

AACT is working hard to expand our library of classroom resources for AP Chemistry teachers. Do you have a great AP demonstration, activity, or lesson about acid-base chemistry that you would like to share with the community? We are proud to feature teacher-submitted activities in our classroom resource collection. If you want to share something you use in your classroom with the community, please send it along for consideration.