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Lesson on Surface Tension

Physics | 7-14 yrs | Interactive, Learning Pod

What makes the water droplets hold on to each other and form drops?

“Geek!” called out the back-benchers to Eeshan Iyengar, the school topper. He had just answered a question asked by the science teacher on surface tension. “Why don’t you answer the question?” defended Eeshan’s friend Nitin. “Quiet class!” the teacher broke up the verbal fight.

It was a hot summer afternoon in Alleppey, the place where Eeshan lived with his father, a farmer and mother, a laborer in the coir industry. It was this humble background that made Eeshan work hard.

Nitin was well to do and his parents had helped in Eeshan’s enrollment at the school, as he was a bright boy. He was also a positive influence on Nitin.

Eeshan had explained to Nitin a few things already about surface tension, to help him answer the questions in class. The bell rang and the children rushed out as it was the last period of the day. “Aren’t you coming?” asked Eeshan. “No, I have to stay back for football practice,” said Nitin. Eeshan bid his friend goodbye and headed home.

The next day Eeshan had to help out his mother with household chores as she was sick and his father could not miss a day at work. After taking care of his mother all day Eeshan stared at the wall poster in the hall area which Nitin had gifted him. It was a poster of the scientist Albert Einstein. “I miss Nitin. Oh well, I will catch up with him in school tomorrow,” he thought to himself.

The next day in school he saw his classmates in a group talking very seriously to each other. He wondered what had happened as they all looked gloomy. To his shock, he found out that Nitin had been kidnapped the day before from school.

His football practice had been cancelled and while he was probably waiting for his driver to pick him up, someone kidnapped him. On further inquiry, he found out that the police concluded that Nitin had been kidnapped, from the evidence of some shattered glass and a broken toilet door. They thought Nitin must have locked himself in the bathroom to escape his kidnappers.

Eeshan was shattered and had to find his friend. He went to the bathroom in question. “You can’t go in. I am fixing the lock,” the carpenter said.

“I just want to check if Nitin left some clues. There must have been a reason why he went straight to the bathroom,” said Eeshan.

“The police didn’t find anything and you want to waste my time by playing detective? I will be back with the tools and you need to be out of here by the time I am back.”

Eeshan looked around and saw hand wash in a plastic lid, which he recognized was from Nitin’s tiffin box. He rushed towards the canteen’s kitchen and got a vessel of boiling hot water. He placed the vessel carefully in the sink. As the steam went towards the mirror, he saw words appear on the mirror.

“School janitor Prakash kidnapping me. Please inform the police-Nitin class 8 D.”

“Nitin! You paid attention!” exclaimed Eeshan and ran to the principal’s police, who in turn informed police.

The janitor was taken into custody and it was discovered that Nitin was at the janitor’s friend’s abandoned plot. Thankfully he was unharmed. Nitin’s parents thanked Eeshan profusely and Eeshan was glad to have his friend back.

The next day at school, “But how did you know where to look and how to look?” asked the other children.

Nitin spoke, “You remember the lesson on surface tension? What makes the water droplets to hold on to each other and form drops, or resist an external force? I poured the hand wash in the bowl of water and dabbed the end of my handkerchief in it. I wrote the secret message before the janitor could break open the door.”

Eeshan spoke. “The message dried up and when I placed a vessel of boiling water under it and steam passed through it, the words reappeared. The steam is also made of water molecules. The tiny droplets stuck to the mirror because of surface tension. The hand wash broke the surface tension of the water droplets as wherever there was soap the water didn’t form droplets and condense. The words written with the soap solution stood out clearly against the foggy background of the mirror.”

“I had no idea a simple lesson on science could save Nitin’s life! You guys made us realize the importance of paying attention!” spoke one of the children.

“Let us start calling Eeshan, Einstein Iyengar!” suggested Nitin.

The other children agreed, which made Eeshan really happy. He knew that he would help people by being Einstein Iyengar and in turn, also make friends.

Looking for more physics articles and videos? Go to: Physics for Kids.