Indicator Sponge

INTRODUCTION:

This purpose of this experiment is to observe the color changes in a sponge that is saturated with an acid-base indicator in different liquids. What would happen if we were to change the liquid? Would the reaction still be the same or would it change?

MATERIALS:

• Beakers, 500-mL or Larger

• Tongs

• Indicator Sponge-Order from FlinnSci.

• Red and Blue Food Coloring

• HCl, 1M, 100 ml

• NaOH, 1M, 100 ml

PROCEDURE:

1. Add 50 ml of HCl solution to a large beaker. Fill the beaker about ¾ full with tap water.

2. Add red enough food coloring until the solution is a deep red color.

3. Add 50 ml of NaOH solution to another beaker. Fill the beaker about ¾ full with tap water.

4. Add enough blue food coloring until the solution is a deep blue color.

5. Slowly place the red sponge halfway into the beaker containing acid solution and write your observations. Completely submerge the sponge and remove it out to see changes. By using a tong ( or gloved hand), squeeze it out as much red acid solution as possible back into the acid beaker.

6. Slowly place the blue sponge halfway into the beaker containing base solution and write your observations. Completely submerge the sponge and remove it out to see changes. By using a tong ( or gloved hand), squeeze it out as much blue base solution as possible back into the base beaker.

SAFETY:

Hydrochloric acid solutions are toxic by ingestion and are corrosive to body tissues. NaOH is corrosive to skin and eyes. Wear chemical splash goggles, chemical-resistant gloves, and a chemical-resistant apron. Review current Material Safety Data Sheets for additional safety, handling, and disposal information.

PICTURES:

SCIENTIFIC PRINCIPAL:

pH indicators are weak acids or bases that exist as natural dyes and indicate the concentration of H+ (H3O+) ions in a solution via color change. pH indicators exist as liquid dyes and dye-infused paper strips. They are added to various solutions to determine the pH values of those solutions. Whereas the liquid form of pH indicators is usually added directly to solutions, the paper form is dipped into solutions and then removed for comparison against a color/pH key. Our project serves to test the principle behind pH indicators by using different colored sponges. (blue and red). One for the acid while the other for the base.

+ Observations...

When the red sponge was dipped into HCl, it turned blue. Whereas, when the blue sponge was dipped into NaOH, it turned red.

+ Analysis and Discussion...

The project served to show how acids and bases work. Typically acids have pH below 7 with colors ranging from green to orange-red. Whereas, bases have pH higher than 7 with colors ranging from blue to purple. Therefore, dipping a red sponge is red acid will turn it blue and vice versa for the base.

+ Conclusion...

This project has taught how to correctly identify an acid or a base. We have also learned that using different liquids like water instead of NaOH and HCl will not produce the same results. Because there would be no color change from the use of acids and bases.

REAL LIFE APPLICATIONS:

Acids and bases can be found in everyday life from the food we eat to the detergents we use. As its name suggests, citric acid is found in citrus fruits—particularly lemons, limes, and grapefruits. It is also used as a flavoring agent, preservative, and cleaning agent. Produced commercially from the fermentation of sugar by several species of mold, citric acid creates a taste that is both tart and sweet. The tartness, of course, is a function of its acidity, or a manifestation of the fact that it produces hydrogen ions. There are plenty of acids found in the human body, including hydrochloric acid or stomach acid—which, in large quantities, causes indigestion, and the need for neutralization with a base. Nature also produces acids that are toxic to humans, such as sulfuric acid. Baking soda, known by chemists both as sodium bicarbonate and sodium hydrogen carbonate, is an example of a base with multiple purposes. Baking soda is also used in fighting fires, because at high temperatures it turns into carbon dioxide, which smothers flames by obstructing the flow of oxygen to the fire. Of course, baking soda is also used in baking, when it is combined with a weak acid to make baking powder.

INVESTIGATION QUESTIONS:

+ Why did we use a sponge?

The sponge is an acid-base indicator. Meaning it helps determine when pH is high (basic) or low (acidic).

+ Why did the sponge turn red when dipped in NaOH?

The sponge turned red because it was a basic solution mixed with blue food coloring. Therefore, the blue sponge turned red to show that the solution had a high pH (basic).

+ Why did the sponge turn blue when dipped in HCl?

The sponge turned blue because it was an acidic solution mixed with blue food coloring. Therefore, the red sponge turned blue to show that the solution had a low pH (acidic).

+ What is an acid-base indicator? And some examples?

Acid - base indicators (also known as pH indicators) are substances which change color with pH. They are usually weak acids or bases. Phenolphthalein is a prime example of a pH indicator.

+ Why the need for gloves?

Gloves are part of the safety precautions because we are working with acids and we want to prevent any skin contact with the acid. Especially if you use your hands to squeeze out the solution after the use of each sponge.