Worksheet

A Balloon and a Basketball in the Climate Chamber

Grade 7 physical science: analyze climate-chamber data for a helium balloon and a basketball and use a particle model to explain volume, pressure and frost.

Grade 7ScienceInteractive · Printable

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Single worksheet
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1 NGSS standard
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11 questions
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Details

Format: Interactive · Printable
Grade: Grade 7
Subject: Science
Question types: Fill in the blank, Multiple choice, Sorting, Short answer

About this worksheet

What students practice

Students use a particle model to explain how adding or removing thermal energy changes the volume or pressure of a gas.
Students analyze temperature, volume and pressure data to predict how a gas will behave.
Students use boiling points and a particle model to predict changes of state.

How to use

Have students sketch the helium atoms in the balloon at 40 °C and at −20 °C before they answer section 1. Use the last question as an exit ticket or a short homework task.

Curriculum

NGSS standard covered

MS-PS1-4

Model how adding or removing thermal energy changes particle motion, temperature and state of a substance.

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Name Date

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)
20	10	157
40	10.7	168
0	9.3	146
−20	8.6	136

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.

Which explanation of the balloon's smaller volume at −20 °C fits the particle model best?

A. Some helium atoms turned into a liquid and settled at the bottom of the balloon.
B. Cold from the chamber leaked into the balloon and pulled the rubber inward.
C. Each helium atom shrank as it cooled, so the same atoms took up less space.
D. The atoms lost energy and hit the rubber less hard, so the balloon got smaller.

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?

A. The ball held fewer particles than the balloon, so the chamber's temperature changed them less.
B. The ball's stiff cover stayed the same size, so faster or slower particles changed how hard they pushed on it.
C. The air in the ball is a mixture, so its particles kept the same speed while the helium atoms sped up and slowed down.
D. The pressure sensor added air to the ball whenever the chamber warmed, and let air out whenever it cooled.

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?

A. About 10.0 L, the same as at 20 °C
B. Between 10.0 L and 10.7 L, the 20 °C and 40 °C readings
C. Between 9.3 L and 10.0 L, the 0 °C and 20 °C readings
D. About 11.0 L, a little more than at 40 °C

Use paragraph 5. After the test, the balloon measured 10.0 L again back at 20 °C. What does this result show?

A. About the same number of helium atoms stayed in the balloon through the whole test.
B. The cold made new helium atoms form, and they filled the balloon back up as it warmed.
C. The balloon's rubber stretched in the cold, so it now holds 10.0 L even when it is cold.
D. The helium atoms had stopped moving at −20 °C and started again when it warmed up.

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
Substance	Boils/condenses at (°C)
Water	100
Oxygen	−183
Nitrogen	−196
Helium	−269

Sort each change by what happens to the average speed of the particles named.

Helium atoms in the balloon as the chamber goes from −20 °C to 0 °CAir molecules in the ball as the chamber goes from 40 °C to 20 °CAir molecules in the ball as the chamber goes from 0 °C to 40 °CHelium atoms in the balloon as the chamber goes from 20 °C to −20 °CWater molecules in the drops on the ball as it warms in the 20 °C hallway

Particles speed up on average	Particles slow down on average

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?

A. Helium turns liquid when its atoms stop moving and stick in place.
B. Helium would turn liquid at 0 °C, the same temperature at which water freezes into ice.
C. Helium would turn liquid at −269 °C, once its atoms are slow enough to stay close.
D. Helium turns liquid once the balloon shrinks to about half of its 20 °C volume.

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.

Use paragraph 5. Where did the white frost on the basketball come from?

A. Water vapor in the hallway lost energy to the cold ball, and its molecules locked into ice.
B. The cold ball gave off cold, which turned some of the hallway air into ice.
C. Air from inside the ball leaked out through the valve and froze on the cold cover.
D. Nitrogen from the hallway air cooled on the cold ball and froze into a thin white solid layer.

10.

Suppose a different chamber could hold the balloon at −40 °C. Based on Tables 1 and 2, what would most likely happen?

A. The balloon would fill with liquid helium, because −40 °C is below its boiling point.
B. The balloon would grow larger, because the helium would freeze and expand like ice.
C. The balloon would be smaller than 8.6 L, and the helium would still be a gas.
D. The balloon would stay at 8.6 L, because helium had stopped shrinking at −20 °C.

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.