Brother Gregory Investigates End
End Brother Gregory's Dinner
Left Return

B

Research Assistant Wanted

Assistants

Brother Gregory wants you to help him find answers to various questions about the physical structure of matter, atoms, and related subjects. In these investigations he will ask you a question and give you the tools to find the answer. You then become his research assistant. You must carry out the experiment, gather data, analyze your results and give Brother Gregory the answer he seeks.


B

The Lowest (and Coldest) Temperature

Winter

"Look at this!" exclaimed Brother Matthew when he saw that his friend and fellow scientist, Brother Gregory, had just arrived in the Monastery kitchen.

"What?" asked Mendel, picking up one of Brother Victor's new loaves of bread and breaking himself off a warm chunk. "Werrt errr yoooo doing neerr?" biting deeply into the fresh, delicious new bread and filling his mouth.

"Here, in the sink, look at these bottles," replied his friend, translating the question correctly as a polite inquiry. He pointed a about a dozen wine bottles floating around in the warm, soapy, washing-up water in Brother Victor's sink. Mendel peered through the steam rising from the hot water and saw nothing more remarkable than empty bottles bobbing around in the dirty water.

Trapped gas

"What's happening?" he asked, more than a bit puzzeled by his friend's excitement.

"Look closely," Brother Matthew told him, "and watch what happens to this bottle, here." He pointed at one particular wine bottle that was floating upside down in the water. Mendel looked closer. He saw that air had been trapped in an ordinary wine bottle, which, because it was upside down in the water, was bobbing up and down, supported by the air inside.

Brother Matthew poured cold water on the sides of the floating bottle, and, as the two monks watched, the air inside the bottle contracted and its volume became smaller. With what looked like less air inside the bottle, it began to sink. As the bottle sank into the warmer washing up water, the air inside the bottle warmed up again, expanded, and the bottle floated higher in the water.

B "Interesting," murmured Brother Gregory, "do that again." Brother Matthew was only too glad to oblige. "What do you make of it?" he asked after a number of repeats.

"The air trapped in the bottle takes up less volume as it is cooled down, and takes up more volume as it is heated," he said at last.

"I agree," said Brother Matthew, "the colder it gets, the smaller the volume of a gas trapped inside." He pushed the bobbing bottle with his finger. "You, know," he said thoughtfully, "this gives us a way to find the lowest, and thus coldest, temperature that it is possible to reach."

"Of course!" exclaimed Brother Gregory, his eyes lighting up, "if we keep cooling the air in the bottle, we will reach a point where volume of the trapped gas is so small it vanishes! That will be the lowest possible temperature!"

"Exactly, but I doubt if we can find a way of cooling the wine bottles down to the absolutely lowest temperature," said Brother Matthew, sadly. "We don't have the equipment, or the resources. Even if we did, at those very low temperatures some very strange things may happen that we wouldn't like. The experiment sounds good in theory, but I don't think anyone could ever reach such a low temperature."

"Don't give up," Brother Gregory insisted, "we can still learn what the lowest temperature is, even if we can never reach it."

"How?" asked his friend, shaking his head.

"I'll get my research assistants on it right away," Brother Gregory told him, and he did.

B

Tools of the Trade

  1. Brother Gregory will give you three different gasses.

  2. One at a time, put a sample of the gas into an inverted tube surrounded by water.

  3. Measure the volume of the gas trapped in the tube.

  4. Increase the temperature of the water and hence the temperature of the gas.

    The Equipment

  5. Measure the new volume of the trapped gas, and write it down.

  6. Do this several times.

  7. Plot a graph of temperature (along the bottom of the graph) against the volume of gas you observed at that temperature (up the side of the graph)

  8. Draw a line through all the points on your graph.

  9. Now extend the line (use a ruler) until it crosses the line of zero volume for the gas.

    Graph

  10. Read off the temperature on the scale along the bottom of your graph. This will be the lowest (coldest) possible temperature that can be reached.

  11. What is it?


Start Here Measure the Gasses
find out how three gasses respond to changes in temperature.


© 1999 Professor John Blamire
Science at a Distance