A N A U T H E N T I C I N T E R N E T - B A S E D L E S S O N A N D P R O J E C T B A S E D L E A R N I N G A P P R O A C H

Acids, Bases, & Salts

Learning Objectives

Students will be able to:

Generate or interpret molecular representations (words and/or pictures) for acid or base solutions

Provide or use representations of the relative amounts of particles in acid or base solutions to estimate strength and/or concentration

Use common tools (pH meter, conductivity, pH paper) of acid or base solutions to estimate strength and/or concentration

Specifically,

• Compare/contrast acids and bases of varying strength. (Given acids or bases at the same concentration)

• Compare/contrast acids and bases of varying solution concentration. (Given acids or bases of the same strength)

• Compare/contrast acids and bases of varying strength and concentration combinations. (Given examples like: Concentrated solution of a weak acid or base; Concentrated solution of a strong acid or base; Dilute solution of a weak acid or base; Dilute solution of a strong acid or base

• Give examples of different combinations of strength/concentrations that result in same pH or conductivity values.

Background

This lesson is part of an ongoing investigation of acids, bases, and salts.

Students will further investigate the properties of acids and bases.

Students will have already tested household products they brought in from home, and used pH paper/Universal Indicator to determine the pH of those substances.

Students learned about acids, bases and the pH scale by using indicators to test different beauty products that are sometimes advertised as “pH-balanced” (e.g. shampoos, deodorants, etc.).

Students were able to discover that the phrase “pH-balanced” has no meaning.

Students created individual spreadsheets that we compiled into a large data table. Taken collectively, students were able to see that some beauty products are weakly acidic, some are weakly basic, and some are neutral.

Students should be able to correlate acidity with lower pH’s and alkalinity with higher pH’s.

Engaging Students with a demonstration.

This demonstration will show students that NYC tap water really is as good as it gets. Students are very familiar with both bottled and tap water.

This is a great demonstration that I developed accidently while running through an experiment at home. It is a discrepant event that students will really be surprised from.

NYC tap water vs. Bottled water

phET Acid-Base Solutions Activity

Students are referred to the worksheet

handout.

Students work in pairs to answer the

worksheet using the phET simulation.

Students are encouraged to discuss their

observations with their partners.

At the end of the activity, students are

presented with clicker questions on a

series of powerpoint slides

Student directions Acid Base Solutions: Concentration and Strength http://phet.colorado.edu

4/17/2016 Loeblein Some materials adapted from an activity by Lancaster /Langdon

Learning goals: Students will be able to

a) Generate or interpret molecular representations (words and/or pictures) for acid or base solutions b) Provide or use representations of the relative amounts of particles in acid or base solutions to

estimate strength and/or concentration

c) Use common tools (pH meter, conductivity, pH paper) of acid or base solutions to estimate strength and/or concentration

Prelab:

1. Water molecules are not shown. Each beaker contains the same volume of solution;

Key: = HA (unreacted acid) = A- = H

+ (or H3O

+)

1a.Which might be the label on Beaker C?

A. 0.01 M HC2H3O2 B. 0.1 M HC2H3O2 C. 0.3 M HC2H3O2 D. 0.01 M HCl E. 0.3 M HCl

1b. Which beaker would have the lowest pH? A B C D

1c. Explain your reasoning: for both questions

2. You have two beakers. One beaker contains 100 mL of NaOH (a strong base);

the other contains 100 mL of aqueous Na3PO4 (a weak base). You test the pH of each solution. Which of the following statements is true?

a. The Na3PO4 has a higher pH because it has more sodium ions than NaOH.

b. It is possible for the solutions in each beaker to have the same pH.

c. If the pH of the NaOH solution is 12.00, the pH of the Na3PO4 solution has to be greater than 12.00.

d. If the pH of the NaOH solution is 12.00, the pH of the Na3PO4 solution has to be less than 12.00.

Explain your reasoning.

Lab: Visualizing acid strength, concentration, and pH

A. Explore the simulation with your group and discuss these questions. Use the molecular view, pH,

conductivity, and bar graphs.

1. For an acid, what happens to the molecule when it is in a water solution?

2. What is different about what happens to a weak acid molecule and what happens to a strong acid molecule?

3. How do the representations of a weak acid reaction differ from a strong one?

4. If you increase the concentration of an acid, what changes in both types of acids?

Beaker A 0.1 M HCl

Beaker B Beaker C

Beaker D

100 mL 100 mL

NaOH(aq) Na3PO4(aq)

Project Discussion

Students will use their acquired knowledge of acids and bases to create two videos about a household item.

Students will work in groups of 4 and select a household item from a list, gather information, and create two videos about their item, geared towards specific audiences.

In groups, students will decide which of their previous middle school teachers they would like to show their video to for evaluation.

Together they will compose an email to send this teacher requesting participation.

Household Item Choices

(May select another, but it must be colorless in aqueous solution and approved by me first)

Sprite Soda Ammonia White Vinegar Aspirin

Seltzer Windex Washing Soda Tums

Topics to include in filming, but not limited to:

Middle School Video General properties of acids and bases; conductivity Arrhenius definition of Acids and Bases; dissociation equations Classify household item as an Arrhenius acid or base; or if it doesn’t fit

the definition, explain why Describe the pH scale and what it tells us; test results of acids, bases,

and household item with litmus paper, universal indicator

High School Video pH and pOH calculation (how to do the calculation; then do this for the

household item) Bronsted-Lowry definition of acids and bases; balanced hydrolysis

equation Degree of dissociation (strong or weak); degree of conductivity Neutralization reaction (write balanced neutralization equation with

states) Results from titration lab with household item

4-5 points 3 points 2 points 1 points # points earned

Creativity and Use of Media (music, art, acting, computer graphics, etc)

-very creative -very original -visible effort put in to make it interesting -strong use of media to enhance interest

-somewhat original / creative -visible effort put in to make it interesting - good use of media to enhance interest

-somewhat creative -some originality - some effort put in to be creative, could be better -little to no use of media

-little to no creativity or originality - little to no effort put in to make video interesting -little to no use of media

Oral Presentation -very well practiced and planned -fluid pace -not awkward -little to no “dead time”

- well practiced and planned - not awkward - little to no “dead time”

- practiced, but could be better - some awkwardness - some dead time

-not practiced -could be better prepared -awkward -a lot of dead time

Middle School (MS) Level

- MS students understand the main points very well, including most or all specific facts in the video

- MS students understand the main points, but may be unclear on a few specific facts in the video

- MS students understand some main points, but are unclear on many specific facts in the video

-MS students do not understand the majority of the video. The main points of video are unclear

Rubric for Middle School Video

Name AND formula of chemical given (2 pts)

-Name of chemical given-Correct formula of chemical given

# Points Earned=

Properties of chemical given (10 pts)

-Acid or base?-Strong or weak?-Results of test with light bulb tester?-Explain how you know that it’s strong or weak?-Degree of dissociation (high or low) and relation to strength?- Results of test with pH paper? - What pH was it? - [H+] concentration? - [OH-] concentration? - Results of tests with red and blue litmus paper

Arrhenius Theory (3 pts)

- Identify as Arrhenius acid or Arrhenius base, or neither - Explain your identification (2 pts)

Bronsted Theory (3 pts)

- Identify as Bronsted acid or Bronsted base - Explain your identification (2 pts)

Rubric for Chemistry Class Video