Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice Test 2025 - Free Practice Questions and Study Guide

The thermosphere is characterized by its extension into outer space and the phenomenon of increasing temperatures with altitude. As you ascend through the thermosphere, energy from the Sun is absorbed by the sparse gas particles, which leads to significant increases in temperature, often reaching up to 2,500 degrees Celsius or more. This layer is less dense than the layers below it, and because of the high temperatures, it can also reflect radio waves, which makes it important for communication.

The other choices do not accurately reflect the properties of the thermosphere. Weather phenomena are typically confined to the troposphere, which is the layer closest to Earth's surface. The thermosphere is not the coldest layer; in fact, it is one of the warmest due to the absorption of solar radiation. Additionally, while the thermosphere does contain some oxygen, it does not have the highest concentration of oxygen compared to the troposphere, where most of the oxygen we breathe resides.