"Mommy, thank you!" exclaimed little Sam and eagerly took the glass that his mother was offering him. It wasn't just ordinary water. This one was full of tiny, dancing bubbles that cheerfully rose from the bottom of the glass all the way to the surface, where they quietly popped. C-c-c-c, it hissed like a small waterfall.
Sam brought the glass to his lips and took a good sip. Right after that, he giggled so hard that a few drops flew out of his nose. "It tickles!" he laughed. "Those bubbles always tickle my tongue so cheerfully. But... where do they actually come from?"
He looked at his mother with big curious eyes. She just smiled. "That's a good question, Sammy. What do you think?"
Sam wrinkled his nose and thought. "Are they little glass marbles? No, I would feel that. Are they water spirits? Also no, that would be scary."
Just then his older sister Linda walked into the kitchen. She heard her brother's question and her eyes lit up. Linda loved mysteries. "No spirits, Sam," she said importantly. "It's something like invisible air that's trapped in the water."
"Invisible air?" Sam wondered. "And how did it get there? And why does it then fly away?"
Linda thought for a moment. "You know what? Instead of talking about it, let's show you. Mommy, will you help us with an experiment?"
Mother gladly agreed. "Of course, my little scientists. What will we need?"
"An empty plastic bottle, a balloon, some vinegar and baking soda," Linda listed, as if reading from a secret scientific book.
In a moment they had everything ready on the kitchen counter. Mother poured some vinegar into the bottle. It smelled sour, like pickles in a jar. Then she gave Linda a small funnel and Sam helped her pour white powder – baking soda – into the balloon. It was like filling a small sack with mysterious white sand.
"Good, and now the most important part," Linda said tensely. She carefully stretched the neck of the balloon over the neck of the bottle so that the powder wouldn't spill in yet. "Ready, Sam?"
Sam nodded and held his breath.
"Three, two, one... now!"
Linda lifted the balloon up and the white powder poured from it directly into the vinegar in the bottle. And at that moment, things started happening!
Inside the bottle it hissed and rumbled much louder than in Sam's glass. The liquid foamed up and thousands of bubbles rushed in all directions. And the balloon... the balloon started inflating by itself! First it was flat, then its belly rounded out, and it grew and grew until it stood on the bottle like a cheerful red cap.
"Wow!" Sam blurted out and pointed in disbelief. "It's inflating by itself! That invisible air is in it!"
"Exactly!" Linda smiled. "When the baking soda met the vinegar, they made gas together. That's the invisible air that inflated our balloon."
"Gas?" Sam repeated the new word.
"Yes," Mother added. "And exactly the same gas, which is called carbon dioxide, is put under great pressure into bottles of water in the factory. There it dissolves, like when sugar dissolves in tea. And when you open the bottle, the pressure is released and the gas starts escaping from the water in the form of those cheerful bubbles."
Sam looked at his glass, where there were already much fewer bubbles. "So they don't disappear, they just fly away into the air around us?"
"Exactly," Linda nodded. "And when you pour the water into your mouth, those little gas bubbles pop on your tongue and that's what tickles you so pleasantly."
Sam smiled from ear to ear. The mystery was solved. It wasn't magic, but something even better – science that they could try themselves. He picked up his glass and eagerly drank the last sip. There were still a few last bubbles there that cheerfully tickled him goodbye.
"And you know what?" he said importantly afterward. "I think science is the best fun in the world!"
And who knows what other mystery Sam and Linda will discover in their kitchen next time? After all, the world is full of amazing things waiting for someone to discover them.