Friday, April 13, 2007

The Case Of The Hot Chocolate

This month, learn about the greenhouse effect

"What a great day to be outside," said Danielle. She dropped an empty soda can into a bulging trash bag. She and her friend Peter were celebrating Earth Day with their science class by picking up trash in a local park.

"It is really warm out today," Peter agreed. "I wonder what the temperature is."

Danielle spotted their teacher walking over. "Maybe Mrs. Woodward knows." she said.

"Mrs. Woodward, do you know what the temperature is today?" asked Peter as their teacher approached.

"I don't know," replied Mrs. Woodward. "But we can check.

I have some thermometers for an experiment we are doing later Let's go and find out."

Danielle and Peter followed their teacher to a nearby picnic table. Mrs. Woodward handed each of them a thermometer.

Peter peered at the thermometer she passed him. "It's 70 degrees out!" he said.

"Wow! That's very warm for this time of year," said Mrs. Woodward. "You two can hang on to those thermometers until later. Now, it's time for lunch."


Peter and Danielle were eating lunch with their classmates.

As they ate, Mrs. Woodward stood in front of the class. "After lunch, we are going to continue our Earth Day celebration by planting trees," she said. "This activity could help prevent global warming."

Danielle raised her hand. Mrs. Woodward called on her. "How does planting trees help fight global warming?" Danielle asked.

"Trees remove carbon dioxide from the air," said Mrs. Woodward.

"That's interesting," said Danielle. "But how does carbon dioxide affect global warming?"

"Carbon dioxide is one of many gases that surround Earth," replied Mrs. Woodward. "This layer of gases is like a blanket that traps the sun's heat. That process is called the greenhouse effect. But if there is too much carbon dioxide in the air, extra heat will be trapped."

"And that can cause global warming?" asked Danielle.

"That's what scientists say," said Mrs. Woodward. "OK. It's time to finish eating and then we can plant some trees."


As Danielle and Peter finished their lunch, they each had a small piece of chocolate left over.

"Are you going to eat that?" asked Peter, eyeing Danielle's chocolate. "If not, I'll take it."

"Sorry, but I am going to save it for later," said Danielle.

"Oh, OK. I'll save mine too" said Peter. "I'm going to put mine in my sandwich container. Do you want to put yours in there?" "That's OK," said

Danielle. "I'll just leave it here." She placed her chocolate candy on the picnic table. Peter placed his in a container and wrapped a piece of plastic wrap over the top.

"Let's go help with the planting of the trees," said Peter.


Read the story below. The use the materials listed at the end to solve the mystery.


"Planting trees is hard work!" said Peter a little later. He wiped sweat from his forehead.

Danielle patted down the dirt around a newly planted tree. "I know. Our chocolate would taste great right now," she said.

"I'll get them," said Peter.

A minute later, Peter returned with the two chocolate candies. He handed one to Danielle.

"Oh no!" said Danielle as she unwrapped her candy. Melted chocolate oozed from the wrapper and dripped onto the dirt. "Our chocolate is ruined!"

She looked over at Peter. He had his back turned to her.

"Hey," she said. "Isn't your chocolate melted too?"

"Um … no," he said, popping the piece of chocolate into his mouth. "Mine must have stayed cool because it was covered with plastic wrap," he said.

Danielle looked at Peter suspiciously. "You took my chocolate, didn't you?" she exclaimed, sounding angry.

"No I didn't!" said Peter. "Why would I do that?"

"It was your chocolate that melted!" said Danielle. "I can prove it." She stomped toward the picnic tables. Peter followed her.

Danielle picked up one of the thermometers from the picnic table. She placed it inside Peter's plastic container and covered it with his plastic wrap. She placed the other thermometer directly on the picnic table next to his container. "We'll know the truth soon," she said.

A half hour later, Danielle peered at the two thermometers. "I know whose chocolate was melted!" she said.
solve the mystery Whose chocolate treat melted?

To solve the mystery, grab these materials:

* plastic wrap
* scissors
* plastic container (large enough to hold a thermometer)
* 2 thermometers
* large rubber band
* lamp or sunny windowsill

Cut a piece of plastic wrap large enough to cover the top of the plastic container. Place one of the thermometers inside the container. Lay the plastic wrap over the container and use the rubber band to hold it in place. Put the container beneath a lamp or on a warm, sunny windowsill. Place the other thermometer next to the container. Position the lamp so that it is equally far away from each of the thermometers. After 30 minutes have passed, check the temperature on each thermometer. The thermometer that is warmer is the one that solves the mystery.

By Britt Norlander, Scholastic SuperScience, Apr2007