Page 133 - Demo

“Your Safer Source for Science”
Acids, Bases and Indicators
131
Acids, Bases and Indicators— Demonstration Kits, continued
Disappearing Rainbow—
Chemical Demonstration Kit
By: The Flinn Staff
Your students will love this colorful demonstration that is always a favor- ite at science conventions. A colorless solution is added to each of six seemingly empty beakers. A second colorless solution is then added and each of the six resulting solutions turns a different color of the rainbow. Add more of the first solution and the rainbow of colors disappears. Challenge your students to explain these amazing observations.
The secret is the small amount of indicator or mixture of indicators placed in each beaker before the demonstration. The first solution is hydrochloric acid which keeps the indicators colorless. The second solution is sodium hydroxide which raises the pH and activates the indicators causing a spectrum of color to appear.
Concepts: Acid–base indicators.
Time Required: 15 minutes
Chemicals Provided: Sodium hydroxide solution, hydrochloric acid solution, indicator solutions of violet, blue, green, yellow, orange, and red.
Dry Ice Color Show—
Chemical Demonstration Kit
By: Lee Marek, Retired
Naperville North H.S., Naperville, IL
Watch as thick white vapor clouds pour up and out of the bubbling caul- drons on your demonstration table! This eye-catching dry ice demo is sure to get a “cool” reaction from your students! It makes a great demo to try at Halloween or any time you want to put on a colorful acid–base show during the year. Just add chunks of dry ice to various acid–base indicator solutions and observe the brilliant color changes. Teach students about sublimation and other properties of dry ice. Discuss pH and acid-base indicators. Write the chemical equation for the formation of acid from the dry ice. Demonstration Notes included.
Concepts: Sublimation, acid–base indicators.
Time Required: 10 minutes
Chemicals Provided: Ammonia solution and indicator solutions of bromcresol green, bromthymol blue, methyl red, phenol red, and universal indicator.
Note: Five dry ice nuggets (walnut-sized) are required.
Hydrolysis of Salts—Acidic, Basic or
Neutral? Chemical Demonstration Kit
By: John Wass
Western Branch H.S., Chesapeake, VA
Acids are acidic, bases are basic, and salts are neutral—right? Not exactly! Teach your students that certain salts dissolve in water to produce acid solutions and others produce basic solutions. Using universal indicator in Petri dishes displayed on the overhead projec- tor, show your students a colorful pH rainbow—made from the simple hydrolysis of salts. Write and discuss the hydrolysis reactions for five different salts with water. A table of acid–base properties of common cations and anions in aqueous solutions is provided for your conve- nience. Demonstration Notes included.
Concepts: Acids and bases, pH, hydrolysis of salts.
Time Required: 10 minutes
Materials Provided: Aluminum chloride hexahydrate, ammonium chloride, sodium bicarbonate, sodium chloride, sodium phosphate, universal indicator solution, five overhead dishes, stirrers.
Note: An overhead projector is recommended for this demonstration.
See free video at flinnsci.com.
Disappearing Rainbow—Chemical Demonstration Kit AP8979
Before
Catalog No.
Description
Price/Each
AP8979
Disappearing Rainbow—Chemical Demonstration Kit
$41.65
After
Dry Ice Color Show—Chemical Demonstration Kit AP6201
Catalog No.
Description
Price/Each
AP6201
Dry Ice Color Show—Chemical Demonstration Kit
$25.30
ACIDS, BASES AND INDICATORS—DEMONSTRATION KITS continued on next page.
Hydrolysis of Salts—Acidic, Basic or Neutral? Chemical Demonstration Kit
AP6187
Catalog No.
Description
Price/Each
AP6187
Hydrolysis of Salts—Acidic, Basic or Neutral? Chemical Demonstration Kit
$28.20