It was Friday, and Bobby felt like he might explode.
He couldn't wait for the weekend.
He was going to see a football game with his dad on Sunday!
"I brought my bottle,"
he said as he walked into Kids Central.
"Great," Miss Shelly said.
"Then get ready to make a sugar and yeast balloon."
"Whatever that is, it sounds cool!" Bobby said.
"You know sugar gives you energy, right?
We're going to give yeast some sugar," Miss Shelly said.
"What do you think will happen?
Will the sugar and yeast blow up our balloons?"
Miss Shelly blew air into a balloon.
"Or not?" She let out all the air.
"Yeast makes bread rise," Jason said.
"So I think yes, it will make our balloons blow up."
"How can sugar and yeast blow up a balloon?" Bobby asked.
He shook his head.
"I don't think it will work."
"Let's try and find out," Miss Shelly said.
"Drop one tablespoon of sugar into your bottle.
I'll come around with warm water."
Bobby carefully spooned the sugar into his bottle.
He shot his arm up in the air.
"I'm ready for water, Miss Shelly!"
Miss Shelly poured warm water into his bottle.
"Now shake!" she said.
Bobby shook as hard as he could.
"That's good enough, Bobby.
Next add the yeast.
Then put the balloon on.
Gently shake it up!"
Bobby emptied the packet of yeast into the bottle.
He put a blue balloon on the top of the bottle.
Then he shook the bottle again, gently.
"Nothing's happening," he complained.
"Be patient," Miss Shelly said.
"Let's go outside while we wait."
"Oh!" Izzie shrieked when they got back.
"My balloon is getting bigger!"
Everyone ran to Izzie's bottle on the table.
Bobby dashed to his seat.
"Mine's growing too!"
"That is so weird,"
Jason said, examining his own balloon.
"Who's blowing it up?" Nina asked.
"How is it getting bigger?"
"The sugar and the yeast are doing it.
Yeast is actually alive, you see.
But it's in a quiet, sleeping stage in the packet.
When mixed with water and sugar, it becomes active again," Miss Shelly explained.
"When yeast eats sugar, it creates gas that fills the balloon.
The balloon gets bigger to make room for the gas.
Just like it gets bigger when we blow into it!
Does that make sense?" Miss Shelly asked.
A tall man entered the gym.
"What's going on in here?" he asked.
"Dad! Look at this!" Bobby shouted.
"We mixed yeast, sugar, and water in a bottle.
That created gas that blew up this balloon!"
"That sounds interesting," Bobby's dad said.
"And in a few hours, you'll see what happens when the yeast runs out of sugar to eat," Miss Shelly said.
"What? You mean there's more?" Bobby asked.
"Take your balloon home, and we'll watch it there," his dad said.
Bobby was thrilled.
He'd get to watch football and his balloon with his dad.
It was going to be a great weekend!
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