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A Balloon and a Basketball in the Climate Chamber

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A Balloon and a Basketball in the Climate Chamber

Use a particle model to explain what happens to gases as a test chamber warms and cools.

Warming and cooling two gases

Read the passage and study Table 1. Then answer the questions.

The Cold Room at the Gear Lab

1A university near Granite Falls runs a sports gear lab. Its most popular room is the climate chamber, a box the size of a small bedroom that engineers can cool to −20 °C or warm to 40 °C. In it, they test how running shoes, jackets and game balls behave in winter and summer weather. Before the city's winter road race, engineer Dr. Yewande Okonjo invited two seventh graders from the race's volunteer crew, Rukmini Iyer and Callum Byrne, to run a test of their own.

2The students brought a balloon filled with helium, like the ones tied to the race's finish-line arch, and a basketball pumped up in the gym. Helium is a pure substance made of single atoms. The air in the basketball is mostly nitrogen and oxygen molecules. Dr. Okonjo tied the balloon loosely to a hook so it could float freely, and she set the basketball on a rack. A camera measured the size of the balloon, and the lab's software turned the size into a volume. A small sensor screwed into the ball's valve read the total pressure of the air inside it. For comparison, the air pressure outside the ball was about 101 kPa (kilopascals).

3The chamber started at 20 °C. Then Dr. Okonjo changed the temperature in steps and held each step for one hour, so that the balloon and the ball had time to reach the temperature of the chamber. The basketball's rubber cover is thick and stiff, and its size did not change enough to measure during the test.

4In science class, Rukmini and Callum had learned that all matter is made of tiny particles that are always moving. The temperature of a substance is a measure of the average kinetic energy, or energy of motion, of its particles. In a gas, the particles are far apart and move freely, bumping into one another and into the walls of their container.

5When the test ended with the chamber at −20 °C, Callum carried the basketball out into the 20 °C hallway. Within a few seconds, a thin white frost covered it. A few minutes later, the frost had turned into tiny drops of water, and after half an hour the ball was dry. Right after that, Dr. Okonjo returned the chamber to 20 °C, and an hour later the balloon measured 10.0 L again.

Table 1. Climate Chamber Readings (after 1 hour at each temperature)
Chamber temp. (°C)Balloon volume (L)Ball pressure (kPa)
2010157
4010.7168
09.3146
−208.6136
1.
Use Table 1. Compare the readings at 20 °C and at −20 °C.

As the chamber cooled from 20 °C to −20 °C, the balloon's volume fell by L and the pressure in the ball fell by kPa.

2.
Which explanation of the balloon's smaller volume at −20 °C fits the particle model best?
Question 2 options
3.
The balloon changed size as the chamber warmed and cooled, but the basketball's change showed up as pressure instead. Which explanation fits paragraphs 2 and 3 best?
Question 3 options
4.
Suppose the chamber is set to 30 °C and held there for an hour. Based on Table 1, what will the balloon's volume most likely be?
Question 4 options
5.
Use paragraph 5. After the test, the balloon measured 10.0 L again back at 20 °C. What does this result show?
Question 5 options

Particle speed and changes of state

Use Table 1, Table 2 and paragraphs 4 and 5. Water freezes and melts at 0 °C.

Table 2. Boiling Points at Normal Air Pressure
SubstanceBoils/condenses at (°C)
Water100
Oxygen−183
Nitrogen−196
Helium−269
6.
Sort each change by what happens to the average speed of the particles named.
7.
Rukmini wonders whether the helium could turn into a liquid if the chamber were made much colder. Which statement fits Table 2 and the particle model best?
Question 7 options
8.
Use Table 2 and the coldest setting of the chamber in paragraph 1.

To condense into a liquid at normal air pressure, the helium would have to be cooled °C below the chamber's coldest setting.

9.
Use paragraph 5. Where did the white frost on the basketball come from?
Question 9 options
10.
Suppose a different chamber could hold the balloon at −40 °C. Based on Tables 1 and 2, what would most likely happen?
Question 10 options

Explain the shrinking balloon

Write your answer in full sentences.

11.
Callum says, “The balloon shrank at −20 °C because cold air got inside it and squeezed the helium atoms smaller.” Do you agree? Write a claim, use evidence from Table 1 and paragraph 5, and use the particle model to explain what happened to the helium atoms as thermal energy was removed.