Jennifer Girard                                                                                                                    Return to Chemistry Menu

Lawrence H.S., Lawrenceville, NJ

Summer 2001

 

Acids and Bases: Their Reactions, Conductivity, Base Indicators

and Neutralization Reaction (4 Lab Lessons)

 

Background

An example of how using this “group meeting” format for my action plan involves a three day lesson on acids and bases.  The class will be broken up into 8 groups.  There are four different activities, which means there will be two groups working on completing each activity.  The groups will conduct the experiment that is assigned to them.  Then based on the data they collected, internet research and textbook information they will be required to answer analysis questions.  This information will then be presented to the class using a power point format.  The following are the topics of the experiments that will be done by each group.

·        Acids and their reactions with metals

·        Electrical conductivity of acids and bases

·        Acid and base indicators

·        The neutralization reaction

These experiments will allow the students to determine some physical and chemical characteristics of acids and bases.  Day one will be spent on collecting data from the experiments.  Day two will be the research phase and finally day three will be the student presentations.  The following sheets should be reproduced and handed out to student researchers.

  

Acids and their Reactions With Metals

 

Directions:

The following is an experiment that your group should complete by the end of class.  Once you have your data collected you will prepare a power point presentation to explain the results you’ve gathered to an audience who have not been exposed to this particular experiment.

 

Procedure: 

  1. Place 3 clean test tubes in the rack.

 

  1. Place one piece of “non-shiny” zinc in each test tube.

 

  1. Cover the zinc in each test tube with a different acid.

 

  1. Record observations below.

 

  1. Repeat the experiment using copper strips

 

Observation and Analysis: 

 

 

 

Reaction (yes/no)

 

Rate of Reaction

(Fast / Moderate / Slow / No Reaction)

 

Gas Produced (yes/no)

 

Acid 1

 

 

HCl + Zn

 

 

 

 

Acid 2

 

 

H2SO4  + Zn

 

 

 

 

Acid 3

 

 

HC2H3O2 + Zn

 

 

 

 

Acid 1

 

 

HCl + Cu

 

 

 

 

Acid 2

 

 

H2SO4  + Cu

 

 

 

 

Acid 3

 

 

HC2H3O2 + Cu

 

 

 

 

  1. Write the balanced chemical equation for each reaction (*Hint* Remember that “no reaction” is a valid observation and conclusion.)

 

 

 

 

 

 

 

2.      Classify the type of chemical reaction that occurred when the zinc reacted with each acid.

 

 

3.      Why did some of the reactions happen at a faster rate than others (*Hint* compare each acid used, what is different about the acids that were involved in the faster reactions?)

 

 

4.      Explain why it is a hazard to store acids in some metal containers, and not others.

 

 

5.      When sugar is placed in water, it disappears and is said to have dissolved.  When magnesium metal is placed in a solution of hydrochloric acid, it also disappears.  Explain why the magnesium did not dissolve.

 

Extension Activity:

 

An advertisement for a trivia game features the following question “Do pearls melt in vinegar?” the “correct” answer given is “yes.”  Write a letter to the trivia company explaining why this is not the case.  Use the internet to research the chemical composition of a pearl.  Include a simplified chemical reaction demonstrating what is really happening with the pearl and vinegar. 


 

Electrical Conductivity in Acids and Bases

 

Directions:

The following is an experiment that your group should complete by the end of class.  Once you have your data collected you will prepare a power point presentation to explain the results you’ve gathered to an audience who have not been exposed to this particular experiment.

Procedure

Simply defined electricity is the energy associated with electrons that have moved from one place to another.  A substance that can conduct electricity must have moving negative charges.

  1. Fill a beaker ¼ of the way full with water.  Test the water to see if it conducts electricity.  Record observations in the chart below.
  1. Repeat conductivity test for each substance.  Record observations in the chart below.

Observation and Analysis: 

 

 

 

Intensity of light bulb

(very bright, bright, dim)

 

Conducts Electricity?

(yes / no)

 

Control

 

 

H2O

 

 

 

Acid 1

 

 

1M HCl

 

 

 

Acid 2

 

 

1M H2SO4

 

 

 

Acid 3

 

 

1M HC2H3O2

 

 

 

Base 1

 

 

NaOH

 

 

 

Base 2

 

 

KOH

 

 

 

Base 3

 

Ca(OH)2

 

 

 

 

4

 

1 M NaCl (aq)

 

 

 

 

5

 

 

NaCl(s)

 

 

 

  1. Why does NaCl (aq) conduct electricity, but NaCl (s) does not?

 

 

  1. Substance 1- 4 release ions when they are dissolved in solution.  Write the Keq expression for each.
    1. HCl                              [H+(aq)] [Cl- (aq)]

 

    1. H2SO4                          [          ] [          ]

 

    1. HC2H3O2                            [          ] [          ]

 

    1. NaCl (s)                       [          ] [          ]

 

  1. Which ion do all 3 acids have in common?

  

  1. Substance 1- 4 release ions when they are dissolved in solution.  Write the Keq expression for each.

 

    1. NaOH                         [Na+(aq)] [OH- (aq)]

   

    1. KOH                                    [          ] [          ]

 

    1. Ca(OH)2                      [          ] [          ]

 

    1. NaCl (s)                      [          ] [          ]

 

  1. Which polyatomic ion do all 3 bases have in common?

   

  1. Define the term Electrolyte.

 

  1. Explain why acids and bases are electrolytes.

 

  1. List at least three household products that would be considered electrolytes.

 

Extension Activity:

A popular sport drink, Gatorade, promises to replenish your body’s electrolytes when you drink it.  Use the internet to research which ingredient(s) are contained that make this drink an electrolytic solution.  Also research how the body uses electrolytes and why they need to be replenished after exercise.

   

Acid and Base Indicators

 

Directions:

The following is an experiment that your group should complete by the end of class.  Once you have your data collected you will prepare a power point presentation to explain the results you’ve gathered to an audience who have not been exposed to this particular experiment.

Procedure:

  1. Use HCl for all the acid tests (accept for the universal indicator than test all three acids).  Use NaOH for all base tests (accept for the universal indicator than test all three bases).

 

  1. Place one drop of acid on each color of litmus paper.  Record the color change if any.  Repeat this test using the base.  Record the color change if any.

 

  1. Fill a test tube about ¼ of the way full with acid and fill another ¼ of the way full with base.  Place on drop of phenolphthalein in each test tube.  Record the color change if any.

 

  1. Fill a test tube about ¼ of the way full with acid and fill another ¼ of the way full with base.  Place on drop of methyl orange in each test tube.  Record the color change if any.

 

  1. Place one drop of each acid on the universal indicator paper.  Record the color for each acid.  Repeat this test using each base.  Record the color change for each base.

 

Observation and Analysis:

 

 

Acid

Base

Unknown

 

Indicators

 

 

 

Color Change

 

Color Change

 

Color Change

 

Litmus Paper

 

Red

 

 

 

 

 

Blue

 

 

 

 

Phenolphthalein

 

 

 

 

 

 

Methyl Orange

 

 

 

 

 

 

HC2H3O2

 

Ca(OH)2

 

Universal Indicator

HCl

 

NaOH

 

 

H2SO4

 

KOH

 

 

  1. Is your unknown an acid or a base?  How do you know?

 

  1. Why is there a slight color difference between the three different acids?  Between the three different bases?

 

  1. If you were testing an unknown and could only use one indicator which one would you use and why?

 

Extension Activity:

The juice of the red cabbage leaf is a naturally occurring acid base indicator.  Use the internet to research if there are any other naturally occurring pH indicators.  If so what do they share in common with the red cabbage?  What are the differences?  Then collect samples of various cleaning solutions, cosmetic solutions, cough syrups, and beverages that are available in your home.  Based on their functions, predict whether these solutions are acidic, basic, or neutral.  Then design an experiment to verify your predictions.  Be sure to include which indicator you plan to use and why you picked it. 

   

Action of a Base on an Acid

 

Directions:

The following is an experiment that your group should complete by the end of class.  Once you have your data collected you will prepare a power point presentation to explain the results you’ve gathered to an audience who have not been exposed to this particular experiment.

Procedure:

  1. Fill a beaker ¼ of the way full with water.

 

  1. Test the pH of the water.

 

  1. Crush 1 ante acid tablet and place into the beaker with the water.  Add 1to 2 drops of phenolphthalein and record the color below.

 

  1. Test the pH of this solution with the pH meter.

 

  1. Fill a beaker ¼ of the way full with acid.

 

  1. Test the pH of the acid.

 

  1. Crush 5 ante acid tablet and place into the beaker with the acid.  After the reaction stops test the pH of this solution with the pH meter.

 

A pH value of 7 is a neutral substance.

A pH that is below 7 is acidic.

A pH that is above 7 is basic.

Observation and Analysis: 

 

pH

Water

 

Ante Acid + Water

 

Acid

 

Ante Acid + Acid

 

 

  1. Classify the ante acid tablet as an acid or a base.  How do you know?

 

  1. What affect does an ante acid have on an acid?  How do you know?

 

  1. Instead of ante acid the HCl was combined with NaOH what do you think happened to the acid?

 

  1. The reaction between the acid and base is a double replacement.  Write the balanced chemical reaction for the above reaction.

 

NaOH + HCl

 

  1. What are the common names for the products that form when a base reacts with an acid?  Come up with a name for this reaction?

 

Extension Activity:

Design an experiment to test and compare the effectiveness of different over the counter ante acid brands.  Include ante acids in different forms such as liquid, capsule, and tablet.  On the internet research “home remedies” for heartburn and try to incorporate them in your experimental design.  Explain why some of these “remedies” might work.