Neutralization with a Tiny Bottle!? Unlocking the Secrets of Hydrochloric Acid and Sodium Hydroxide Through Microscale Experiments
I’m Ken Kuwako, the Science Trainer. Every day is an experiment.
Have you ever thought, “Using lots of chemicals in science experiments can’t be very good for the environment…”? Fortunately, there’s a clever solution: micro-scale experiments. In this article, we’ll use this eco-friendly approach to explore the neutralization reaction between hydrochloric acid and sodium hydroxide.
What Is a Micro-Scale Experiment?
As the name suggests, a micro-scale experiment is one that uses very small amounts of chemicals. Since less chemical is used, much less waste liquid is produced afterward. That makes it a much more environmentally friendly way to experiment.
For this activity, we used 1 mol/L hydrochloric acid and 1 mol/L sodium hydroxide, along with a tiny dropper container called a “Petit Bottle.”
We added one drop at a time into a test tube while carefully watching the color change of the BTB solution. The goal of a neutralization experiment is to find the exact point where the acid and the alkali perfectly cancel each other out, so paying close attention to every color change is essential.
Discovering the Importance of a Single Drop
In many traditional experiments, chemicals are added in 1 mL portions using a pipette.
With a Petit Bottle, however, you can control the amount one tiny drop at a time. It’s a bit like adding seasoning little by little while cooking until the flavor is just right.
That said, using the bottle takes a little practice. To produce neat, consistent drops, you need to aim carefully so the liquid doesn’t stick to the side of the test tube. This simple technique is actually a great way to develop two important scientific skills: accuracy and reproducibility.
What Happens After the Water Evaporates?
The fun doesn’t end with the color change.
We placed both the hydrochloric acid solution before neutralization and the neutralized solution into separate evaporating dishes, then gently evaporated the water.
What do you think was left behind?
It’s a little difficult to see in the photo, but the dish on the left contains hydrochloric acid with BTB indicator, while the one on the right contains the neutralized solution, adjusted to be slightly acidic. On the right, you can spot a fine white powder.
The White Powder Is Something You Eat Every Day
That mysterious white powder is sodium chloride (NaCl), produced when hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH). In other words, it’s simply table salt.
The neutralization reaction can be written like this:
Hydrochloric Acid + Sodium Hydroxide → Sodium Chloride + Water
Whenever an acid reacts with an alkali, the products are water and a substance known as a “salt.” In this particular experiment, that salt just happens to be ordinary table salt.
One of the most exciting moments in chemistry is seeing an invisible reaction suddenly become visible. After the water evaporates, the dissolved salt appears as tiny white crystals—a satisfying piece of evidence that the reaction really happened.
Perfect for Small-Group Learning
Another advantage of micro-scale experiments is that they require so little chemical that one setup can easily be shared by just two students. Instead of a large group crowding around a single experiment, everyone gets more opportunities to handle the equipment, make observations, and think through the results themselves.
A tiny bottle produced just a tiny pinch of white powder—but inside that powder was the story of one of chemistry’s most fundamental reactions. Sometimes, the smallest experiments reveal the biggest scientific ideas.
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