October 2015

# Sharing chemistry with the community: Chemistry and our health

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Danielle Holdner*, Duke University, Durham NC

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This set of six hands-on activities called Chemistry and Our Health relates the role of chemistry to various aspects of our well-being. Making chemistry concepts relevant to one’s everyday life has been shown to be valuable to student understanding and learning. Participants are exposed to the following chemical concepts: chemical nature of solutions, pH, acid-base indicators, chemical properties of a substance, neutralization reactions and precipitation.

These activities connect chemistry to our health, such as the role of breathing in controlling blood pH, acidosis and alkylosis, acidic nature of soft drinks, degradation and prevention of tooth enamel, acid indigestion and antacids, and the use of calcium alginate gel to treat severe burn victims. In a general science class, these activities can lead to excellent discussions on acids and bases.

After first learning the difference between acidic, neutral and basic solutions using universal indicator, participants investigate the acidity of one’s breath and the substance responsible. Next, they investigate the acidity of various drinks, followed by acid indigestion and the role of antacids. Lastly, the participants learn how to form calcium alginate gel. All activities are easy to prepare and perform. The materials are readily available and, because of the small scale nature of the experiments, are relatively safe.

## Materials

- Water; 0.01 M hydrochloric acid; 0.01 M sodium hydroxide; various drinks such as club soda, Sprite®, milk, apple juice, green tea, Gatorade® and MOM (Milk of Magnesia®) — any drink can be tested but avoid dark colors
- Small plastic dropping bottles filled and labeled with the above solutions
- Universal indicator pH color chart in a plastic sheet protector
- Two pieces of dry ice — grape size or smaller
- Calcium chloride CaCl2 (1% solution) and sodium alginate — colored with food coloring
- One 12-well microplate
- Plastic drinking straw
- Clear, colorless plastic cups — three small (2-oz) and two large (10-oz)
- Side-arm flask with stopper, fitted with plastic tubing
- Toothpicks
- Plastic disposable dropping pipettes
- Small meshed sieve and plastic food storage container

## Advance preparation

It is helpful to color code the bottle tops with permanent markers. This avoids the tops being mixed up.

Check the water to be sure it is neutral — it should produce a green color with the universal indicator. In our case, our tap water was neutral but our deionized water was not.

Prepare calcium chloride and sodium alginate solutions — each solution consists of 1 g of solid per 100 mL of water. Sodium alginate is best prepared by mixing with a blender and chilling overnight in a designated refrigerator for chemicals. Add coloring after the sodium alginate solution sets overnight.

## Procedures

### Activity 1

Put 1 to 2 drops of each (acid, water and base) in separate wells of the microplate. Add 1 drop of universal indicator to each; note color and use universal indictor color chart to estimate pH.

### Activity 2

Half-fill a small cup with water; add enough universal indicator to make a dark green color; using a straw, blow bubbles in the solution and note color change. Using chart, estimate pH.

### Activity 3

Half-fill two large cups with water and add universal indicator to make each dark green; add a small piece of dry ice directly into one cup. Add another piece into the side-arm flask; stopper flask and put the end of the attached hose into second cup. Allow gas to bubble through the solution for a few minutes. Note color change of solution in each cup and estimate pH.

### Activity 4

Place 1 to 2 drops of each drink to be tested into separate wells of the microplate and add 1 drop of universal indictor to each. Note pH of each drink.

### Activity 5

Put 10 drops of water into three wells of the microplate and add 1 drop of universal indicator to each. Add 3 drops of acid to two of the three wells containing the colored water. Add 1 to 2 drops of MOM to only one well containing the acidic water; stir with a toothpick. Note final pH.

### Activity 6

Half-fill a small cup with calcium chloride solution. Using a dropper, add drops of colored sodium alginate solution and allow to stand for about one minute. Do not allow dropper to touch the calcium chloride solution. Strain the mixture through a sieve to capture the calcium alginate gel. The liquid can be re-used to make more calcium alginate. The gel is safe to touch. Wash hands after handling.

For detailed procedures, questions for participants to answer, and other related materials, contact Kenneth Lyle.

## Safety

- Wear goggles or safety glasses, and protective lab gloves.
- Do not handle dry ice with bare hands. Use tongs.
- Do not ingest calcium alginate gel. Wash hands after handling.
- Even dilute solutions of HCl and NaOH are corrosive so avoid skin contact. Wash with plenty of water if there is contact with skin.

## Disposal

- Empty and wash out bottles after each presentation. The tips clog if you do not.
- Wipe out the microplate with paper towel and wash.
- Carbon dioxide and calcium chloride solutions can be disposed of in the sink along with solutions from the dropping bottles.
- Calcium alginate gel can be captured in a sieve and disposed of in the trash.
- Combine acid and base solutions in a beaker to neutralize before disposing. Rinse thoroughly, including squeezing water through the tips. Allow to dry disassembled. Keep tips, bottles and caps for each designated solution in separate plastic storage bags.
- Allow remaining dry ice to sublime.

## Reflections

We have found that people of all ages and backgrounds enjoy performing these experiments — especially learning about the connections to our health. Danielle Holdner has recently joined the Duke Chemistry Outreach Team. Not only was this her first time presenting Chemistry and Our Health but also her first time presenting at any outreach event. The following are her reflections.

Before I engaged with the children and the wonders of chemistry, I reflected on something Dr. Lyle called his “Einstein, Darwin and other great scientific inventors” speech:

> “We, as students, as teachers, as scientists, should be truly honored in being able to guide young minds and how we are given the great chance to teach them about the known facts and theories of science so that they can discover what are now the unknowns in our world, in which may even be future cures for many diseases.”

Throughout planning and presenting, this statement continued to cross my mind. When the students came through the lab doors, my excitement soared, and I felt ready to introduce the chemical concepts and their relationship to our health. The first activity was testing different solutions with universal indicator so students could distinguish its color in acidic, neutral and basic solutions. Extracting the dry ice from its container and adding it to the water was of particular excitement. To the students, solid carbon dioxide was such a unique and unknown substance.

I asked students to make hypotheses, which they enjoyed. There was particular excitement when their hypotheses were shown to be correct. The students were equally enthralled as they tested the pH of various drinks. They were surprised that everyday drinks, including their favorite carbonate drinks, were acidic. Even more surprising to them was that drinking too much of these drinks contributes to the tooth enamel breaking down.

One favorite activity was making the calcium alginate gel. The “colored pearls” of calcium alginate formed right in front of students’ eyes and led to “oohs” and “aahs”. This contributed to their enjoyment. After forming a batch of pearls, the mixture was strained through a sieve. The students were able to hold and “play” with the pearls in their hands. They rolled them in their hands, squished them and placed them on their skin to see how a calcium alginate bandage might feel.

Overall, this experience of sharing gave me a new interest for the scientific concepts that I have already learned. And as Dr. Lyle said, it really was a great honor to teach these young minds.

*Danielle Holdner is a junior attending East Carolina University majoring in Family Community Services. Upon graduation she plans to attend medical school, to practice pediatric medicine.

**Kenneth Lyle is a lecturing-fellow in the department of chemistry at Duke University NC. Powell Family Trust, the Duke-Durham Neighborhood Partnership, and Biogen Idec – Research Triangle Park, fund the Duke Chemistry Outreach Program.

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