I'm supposed to compare the percent composition of gases in the atmosphere at sea level to the percent composition at high altitude..

Would the percents decrease? I don't really understand

Although some gasses (for example pollutants over a city with temperature inversion or water vapor) tend to be concentrated in particular layers, in general the percentages would be the same.

To compare the percent composition of gases in the atmosphere at sea level versus high altitude, you need to understand the concept of air composition and how it changes with altitude.

At sea level, the composition of Earth's atmosphere is relatively consistent and commonly referred to as dry air. Dry air typically consists of approximately 78% nitrogen (N₂), 21% oxygen (O₂), and the remaining 1% is made up of various trace gases such as carbon dioxide (CO₂), argon (Ar), neon (Ne), helium (He), and others.

As you ascend to higher altitudes, the atmospheric pressure decreases. The decrease in pressure affects the gas density and leads to a change in the percent composition of gases. While the relative proportions of nitrogen and oxygen change only slightly with altitude, the concentration of trace gases can vary significantly.

In general, at higher altitudes, the percent composition of gases other than nitrogen and oxygen tends to decrease. This is because these trace gases are present in smaller amounts and are more likely to be affected by the decrease in air density.

For example, trace gases like carbon dioxide (CO₂) and water vapor (H₂O) usually become less concentrated as you go higher in the atmosphere. This is due to multiple factors, including diffusion, convection, and precipitation processes.

It's important to note that the specific changes in the percent composition of gases at different altitudes can be influenced by various factors such as weather patterns, geographical location, and time of year. Therefore, the exact percentage changes can vary depending on the specific conditions and location.

To compare the percent compositions at sea level and high altitude, you can refer to scientific sources, atmospheric data measurements, or utilize online databases that provide information on the composition of Earth's atmosphere at different altitudes.