Weather Stations: Temperature and Pressure

Overview

Children discover the relationship between temperature and pressure in the lower atmospheres of Jupiter and Earth. They chart the increasing temperature as they add pressure to a 2-L soda bottle with a Fizz-Keeper Pump.

What's the Point?

• Atmospheres are made of gases, and those gases press down on each other to create very different properties at the top of the atmosphere compared to the bottom.
• Temperature increases with pressure for the bulk of the atmosphere.
• The Juno spacecraft will measure Jupiter's atmospheric temperatures at different levels and "see" more deeply than any instrument has before.

Materials

• 1 clear 2L plastic beverage bottle with cap (clean, with label removed)
• 1 liquid crystal temperature strip with markings for at least every two degrees Fahrenheit (available in most pet stores or stores that sell aquarium fish)
• 1 Fizz Keeper Pump (available online and in supermarkets): use with adult supervision
• Tape
• Can You Take the (Low) Pressure?, printed preferably in color

For each child:

• His/her My Trip to Jupiter Journal or just the relevant "Temperature and Pressure" pages
• 1 pencil or pen

Preparation

• Tape the temperature strips to the bottoms of the Fizz-Keeper Pumps so that they will hang down inside the bottle when the pumps are screwed into the soda bottles.
• Set out copies of Can You Take the (Low) Pressure?.

Activity

1. Introduce the activity as an experiment to model what an imaginary spacecraft would encounter while descending through Jupiter's atmosphere. Ask them to first consider what Earth's atmosphere is like.

• What is Earth's atmosphere like at high altitudes, where jets fly and at the top of Mt. Everest? Cold. There is less air (lower pressure).
• What term can we use to describe the amount of air something holds? Pressure.
• What is Earth's atmosphere like where we live? Warmer and thicker (more pressure).At sea level? It is thickest at sea level.
• What is Earth's atmosphere made of? Nitrogen, oxygen, and small amounts of other gases such as water and carbon dioxide.
• Why might the atmosphere's temperature and pressure be different at low and high altitudes? Accept all answers. Gently correct any suggestions that the atmosphere is warmer because it is closer to the Sun. Remind them of the scale of the Earth and Sun that they explored in Jump to Jupiter! and Solar System in Your Neighborhood. Even the highest-flying jet is only infinitesimally closer to the Sun than the surface of the Earth.

2. Explain that the children will be using an empty bottle to model how Jupiter's atmosphere changes with depth. Describe how the bottle has the same amount of air inside (pressure) as the room does, and the activity will model the crushing pressures of Jupiter's atmosphere.

• How can we put the air in the bottle under more pressure? By adding more air.

Show the equipment to the children and explain that a Fizz-Keeper pumps air into a sealed bottle. Indicate which colors they should be looking for on the liquid crystal thermometer in order to read the temperature (the directions should be on the package). Ask the children to predict how the temperature inside the bottle will change as more air is added (the pressure increases). Have them record their predictions in their journals.

Safety Notes: This activity involves increasing air pressure within the bottle: ensure that children and teenagers are supervised by adults at all times.
Provide only one set or two sets of bottles, thermometers, and Fizz-Keeper Pumps at a time. Have participants stop pumping once the pressure is high (and it becomes difficult to pump). Do not allow participants to try to unscrew the Fizz-Keeper during the experiment. After the experiment, an adult should gently unscrew the bottles to allow the air inside to cool before using them again.

3. Ask the children to record the air temperature inside the bottle as the air inside it is compressed with sequentially more pumps of the Fizz-Keeper. Have them follow the directions in their journals.

4. Have the children discuss the general trends shown on their plots and note them in their journals.

• Where, on the plot, is the pressure highest? At the bottom of the plot. How many pumps with the Fizz-Keeper correspond to this high pressure? 80 pumps.
• Where on the plot is the temperature highest? To the far right. What is the highest temperature they recorded?
• Where is the pressure lowest? The temperature? In the upper left corner.
• What is the general shape of their plot? A line slanting downward from low pressure and temperature to high pressure and temperature.

5. Invite them to compare their plots with the same kind of plot for Earth's atmosphere, which is shown in their journals and on the Can You Take the (Low) Pressure? poster. Ask them to locate some familiar landmarks on the plot of Earth's atmosphere.

• Is the pressure and temperature high or low at the top of Mt. Everest? At low temperatures and pressures (the upper left) Sea level? At high temperatures and pressures (the lower right). Can you find where the temperature and pressure at your current altitude would lie on this plot?
• Why is the atmospheric pressure lower at the top of Mt. Everest? The pressure is lower at high altitudes because there are fewer molecules of nitrogen, oxygen, and the other gases compared to sea level.

Mountain climbers must bring oxygen with them to breathe when they climb Mt. Everest!

Facilitator's Note: If hot air rises, why is it cooler at higher altitudes? Hot air does indeed rise, but it does not remain hot. It spreads out (expands) and cools as it rises. Hot air balloons must contain their heated air — and continually heat it — in order to rise and stay aloft.

6. Have the children consider how Jupiter's atmosphere changes with depth. Remind them that Jupiter is much more massive than Earth and has a lot more gas. Invite them to imagine that they are spacecraft flying deep into Jupiter's atmosphere. In its lower layers, their spacecraft instruments will detect low pressures and low temperatures at first. Invite the children to draw in their journals what they think they would find in Jupiter's lower atmosphere.

• What do the children predict will happen to the pressure and temperature as their imaginary spacecraft go deeper (lower)? Pressure and temperature will increase.
• Will the pressures and temperatures be the same as we experience on Earth's surface, or will they be higher or lower? MUCH higher! Why? Jupiter is much larger and more massive, so it has more gases pressing down on its lower layers than Earth.
• How did we model this in our experiment? We added gases to the bottle by pumping the Fizz-Keeper.

Add that Jupiter's immense gravity and the leftover heat from its formation provide an internal heat source that is more than two times greater than the heating it receives from the Sun's light.

Conclusion

Explain that the Juno spacecraft will study Jupiter's atmosphere to measure the temperatures at its different levels of pressure — like the children did in this activity and recorded in their journals!

• What kind of instrument do the children think Juno will carry to do this? Thermometer.

Remind the children that the Juno spacecraft will not enter Jupiter's atmosphere, but will take Jupiter's temperature from orbit and "see" more deeply than any instrument has before. Scientists want to better understand what the different levels of Jupiter's atmosphere are made of, how it has such strong winds deep inside, and how the gases are whipped into the bands we see across Jupiter's exterior.