Odile and the Fizzy Cup: reading passage and questions

Odile's uncle put white powder in a cup. "Watch," he said. He poured in a little vinegar.

Fizz! Bubbles rushed up and over the top of the cup. Odile jumped back and laughed.

"Where did the bubbles come from?" she asked. "A gas," said her uncle. "The powder and the vinegar made it."

"That is a chemical reaction," said her uncle. "Two things mixed, and something new came out!" Odile poked the foam.

"Look," said Odile, and she pointed at the cup. "The powder was white. The foam is not!"

In the kitchen, her uncle held up the white powder. "This is baking soda for muffins," he said. "What does it do?" asked Odile.

"It meets an acid in muffins," he said. "An acid is something sour. Bubbles of gas puff them up."

Odile's apple slice turned brown. "Air touched it," said her uncle. "That is a reaction, too."

Her uncle squeezed lemon juice on a slice. "Lemon juice can slow the browning," he said. "Let us see."

Odile's old bike sat in the rain. "Is the bike sick?" she asked. "No," said her uncle.

"That is rust. Iron, water and air make it. Rust is red-brown and crumbly."

That night, Odile saw fireworks go boom. She covered her ears and giggled. They lit the sky red, blue and green.

"Why so many colors?" she asked. "Many colors come from different metals," said her uncle. "Ooh!" said Odile.

Try this with a grown-up. Squeeze lemon on one apple half, then wait an hour.

Look at both halves now. Which half is brown, and which half is not?