Limewater experiment

Roland gives a lecture on the natural sciences, demonstrating there are different types of gas molecules in the air including CO2 and O2 using the limewater experiment.

## Details

During the rain, he had called for Carter and the two witches Anna and Nana to attend their own class – yes, he had decided to open a course on natural science. He was inspired by Stonemason Karl's school. If even a mason can open a school, then could a mechanical engineer open one too? Universal education was at any age the most effective measure to promote the development of civilization.

## Demonstration: Atmospheric gases

Although this world had magic, the laws of physics were still (more or less) the same.

Roland / Chen teaches that there are different kinds of gases in the air. A student asks how one knows if they cannot even see the gases.

Roland decided to use a simple experiment to arouse everyone’s interest.

A candle, a glass, a basin, a bowl of limewater – these were the things he had prepared in advance. Although at this time they had only pale brown glass, far less transparent than the glass of his former time, it was still transparent enough to be used. After all, this simple test didn’t need someone to observe the changing process.

Roland had done this test before once, the test results showed that although there was magic in this world, the rules of nature were still the same as on Earth. He asked Anna to light the candles, and then he put it in the basin.

“When something is burning, it needs to consume gas. This gas is also closely linked with every living organism, if we stop breathing, we will be like this candle. Watch.” Roland put the glass on the candle, and after the flame shook two times, it soon went out.

“It exhausts the air, sir, this is not surprising.” the chief knight spoke in a disapproving way, “Of course we will die without air. For example, if we fall into water.”

“So, do you think that there in the glass is nothing at all?” Roland asked, then he poured the limewater into the basin, the limewater soon flooded into the glass, but it finally stopped when only half was filled.

This experiment was so classic that most elementary school teachers liked to use it as an experiment to increase the interest of the children in natural science. Roland could still remember the shock he felt when his own teacher had demonstrated it. From then on he embarked on the road of science and engineering, with no way to return.

He gently lifted a corner of the glass, and after a few moments bubbles of air could be seen rising out of the limewater.

Then, the clear limewater appeared to be a little bit cloudy, and a little white cloud slowly spread within the glass.

“If there was nothing in the glass, we wouldn’t have seen the changes in the limewater and the air bubbles. This shows that the air contains at least two different kinds of gases. In fact, burning a candle consumes only a part of the air, while the other part is unable to burn. Though it is colorless and odorless, like the former gas, its nature is the complete opposite.”

“Well… That seems to be the case,” Carter thought for a long time to figure out the relationship between the two, “but to know this, what is the use of it?”

“If you can get the former gas, you can let the flame burn longer, and when you obtain the other gas, you can quickly extinguish the flames!” Anna suddenly said.

She was simply a genius, Roland praised her in his heart. Even though there was a small fallacy, when hearing of the different properties of the gases, she could immediately think of several uses. This idea was definitely genius-level. Roland knew that she did not receive any modern education, but even without it, she could quickly think of this point, showing her extraordinary logic ability – at least she was far better than this chief knight.

“Right, it is possible to say that since humans learned to use fire, they were separated from the animals, even though obtaining fire was just a coincidence. Perhaps the lightning hit the trees and lit them, perhaps a rock hit another rock and released a spark. But if no one had noticed it, no one could have tried using it. We would still be the same as the animals. Roland guided them patiently and systematically in the direction he wanted, “The goal of this experiment was to show you that curiosity and thinking were the driving forces of human progress. There are many of similar potential forces in nature, only waiting for us to discover and use them."

## Physics

Also see Limewater chemistry. The first gas is oxygen O2 and keeps the fire going. The second gas is carbon dioxide CO2 and can be used to put out flames (like in fire extinguishers).