Layers of the atmosphere

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Typical top of the troposphere (rounded)

   Place	Height (km)
   Poles	8
   Mid-latitudes	11
   Equator	17

2. 1.

   Bo reads the table. Which explanation fits the troposphere being deepest at the equator?

   • The equator has less water vapor, so the troposphere is taller
   • The ozone layer at the equator pushes the troposphere upward
   • Gravity is weaker at the equator, so air spreads higher
   • Strong heating at the equator lets air rise higher before it cools to match its surroundings

3. Layer boundaries (about, NOAA)

   Boundary	Height (km)
   Top of troposphere	11
   Top of stratosphere	50
   Top of mesosphere	85

4. 2.

   Jun compares layer thicknesses. Which layer is thickest, and how thick is it?

   • The mesosphere, 85 km thick
   • The mesosphere, 35 km thick
   • The stratosphere, 50 km thick
   • The stratosphere, 39 km thick

5. US Standard Atmosphere

   Height (km)	Temperature (°C)	Pressure (hPa)
   20	-56.5	54.75
   32	-44.5	8.68
   47	-2.5	1.11

6. 3.

   Milo compares the 20–32 km and 32–47 km stretches. Which warms faster per km, and by how much?

   • 20 to 32 km, about 12 °C per km
   • 20 to 32 km, about 1.0 °C per km
   • 32 to 47 km, about 42 °C per km
   • 32 to 47 km, about 2.8 °C per km

7. A balloon sounding (example data)

   Height (km)	Temperature (°C)
   4	-10
   8	-37
   12	-57
   16	-57
   20	-55

8. 4.

   Noah looks for the tropopause, where cooling with height stops. Where is it?

   • About 20 km, the highest reading
   • About 12 km, where the cooling stops
   • About 8 km, halfway up the cooling
   • About 4 km, where the weather seems to end

9. US Standard Atmosphere

   Height (km)	Temperature (°C)	Pressure (hPa)
   47	-2.5	1.11
   51	-2.5	0.67
   71	-58.5	0.04

10. 5.

    Temperature falls from −2.5 °C at 51 km to −58.5 °C at 71 km. Which reason does Pia give?

    • The ground heats this layer, and the heat fades with distance
    • Ozone is most plentiful here, so the air absorbs less sunlight and cools
    • Little ozone is left to absorb ultraviolet light, so the air loses heat and cools
    • Pressure rises with height here, which cools the air
11. 6.

    Argon is 0.93% of dry air. Sea-level pressure is 1,013.25 hPa. Partial pressure of a gas = share × pressure. Ren finds the pressure of argon alone at sea level. What is it?

    • About 0.94 hPa
    • About 9.4 hPa
    • About 94 hPa
    • About 790 hPa
12. 7.

    Carbon dioxide rose from about 280 ppm before industry to about 420 ppm now. By what percent has it risen, by Tala's math?

    • About 33%
    • About 0.014%
    • About 140%
    • About 50%
13. 8.

    Oxygen is 21% of the air at the ground and at 11 km, yet a breath holds less oxygen at 11 km. Which reason does Zee give?

    • Oxygen sinks, leaving nitrogen on top, so there is less at 11 km
    • The oxygen share falls to 7% at 11 km, so each breath holds less
    • The air is thinner, so each breath holds fewer molecules though the share is still 21%
    • Planes use up the oxygen at 11 km, so each breath holds less

14. US Standard Atmosphere

    Height (km)	Temperature (°C)	Pressure (hPa)
    0	15.0	1,013.25
    11	-56.5	226.32

15. 9.

    A model says pressure halves every 5.5 km. Ari tests it at 11 km against the table. What does it predict, and how does that compare?

    • About 126 hPa, which is 44% too low
    • About 507 hPa, which is 124% too high
    • About 253 hPa, which is 12% too high
    • About 253 hPa, which is 12% too low
16. 10.

    Pressure 22,632 Pa, temperature 216.65 K. Density = pressure ÷ (287 × temperature in kelvins), in kg/m³. Kira finds the density of the air at 11 km. What is it?

    • About 3.64 kg/m³
    • About 0.289 kg/m³, using 273 K
    • About 0.0364 kg/m³
    • About 0.364 kg/m³