Atmospheric Science Mock Tests

The following passage is an excerpt from an article about atmospheric science. The ozone layer is a region of the Earth's stratosphere that contains a relatively high concentration of ozone (O₃) gas. Often described as Earth's "sunscreen," the ozone layer absorbs 97 to 99 percent of the Sun's medium-frequency ultraviolet light, which is harmful to life. Without the ozone layer, UV-B radiation would reach the Earth's surface in quantities sufficient to cause severe damage to living organisms, including increased rates of skin cancer, cataracts, and immune system suppression in humans, and reduced photosynthetic activity in phytoplankton—the foundation of the marine food web. Ozone is continuously created and destroyed in a natural balance known as the Chapman cycle. In this cycle, ultraviolet radiation strikes an oxygen molecule (O₂), splitting it into two individual oxygen atoms (O). Each free oxygen atom then combines with another O₂ molecule to form ozone (O₃). Ozone molecules are themselves broken down by UV radiation into an O₂ molecule and a free oxygen atom, releasing heat in the process. This continuous cycle maintains a relatively stable concentration of ozone in the stratosphere. However, in the 1970s, scientists discovered that certain human-made chemicals, particularly chlorofluorocarbons (CFCs), were disrupting this natural balance. CFCs are stable compounds that were widely used in refrigeration, air conditioning, foam production, and aerosol propellants. Because they are chemically inert and non-toxic, CFCs can persist in the lower atmosphere for decades and eventually diffuse upward into the stratosphere. There, intense UV radiation breaks them apart, releasing chlorine atoms. A single chlorine atom can catalytically destroy more than 100,000 ozone molecules before being removed from the stratosphere. This catalytic process led to the formation of an "ozone hole" over Antarctica, first documented in the mid-1980s. The Montreal Protocol, an international treaty signed in 1987, successfully phased out the production of CFCs and other ozone-depleting substances. As a result, the ozone layer is slowly recovering and is projected to return to pre-1980 levels by approximately 2060. According to the passage, what is the main reason the ozone layer is essential for life on Earth?

The following passage is an excerpt from an article about atmospheric science. The ozone layer is a region of the Earth's stratosphere that contains a relatively high concentration of ozone (O₃) gas. Often described as Earth's "sunscreen," the ozone layer absorbs 97 to 99 percent of the Sun's medium-frequency ultraviolet light, which is harmful to life. Without the ozone layer, UV-B radiation would reach the Earth's surface in quantities sufficient to cause severe damage to living organisms, including increased rates of skin cancer, cataracts, and immune system suppression in humans, and reduced photosynthetic activity in phytoplankton—the foundation of the marine food web. Ozone is continuously created and destroyed in a natural balance known as the Chapman cycle. In this cycle, ultraviolet radiation strikes an oxygen molecule (O₂), splitting it into two individual oxygen atoms (O). Each free oxygen atom then combines with another O₂ molecule to form ozone (O₃). Ozone molecules are themselves broken down by UV radiation into an O₂ molecule and a free oxygen atom, releasing heat in the process. This continuous cycle maintains a relatively stable concentration of ozone in the stratosphere. However, in the 1970s, scientists discovered that certain human-made chemicals, particularly chlorofluorocarbons (CFCs), were disrupting this natural balance. CFCs are stable compounds that were widely used in refrigeration, air conditioning, foam production, and aerosol propellants. Because they are chemically inert and non-toxic, CFCs can persist in the lower atmosphere for decades and eventually diffuse upward into the stratosphere. There, intense UV radiation breaks them apart, releasing chlorine atoms. A single chlorine atom can catalytically destroy more than 100,000 ozone molecules before being removed from the stratosphere. This catalytic process led to the formation of an "ozone hole" over Antarctica, first documented in the mid-1980s. The Montreal Protocol, an international treaty signed in 1987, successfully phased out the production of CFCs and other ozone-depleting substances. As a result, the ozone layer is slowly recovering and is projected to return to pre-1980 levels by approximately 2060. According to the passage, what is the main reason the ozone layer is essential for life on Earth?

The following passage is an excerpt from an article about atmospheric science. The ozone layer is a region of the Earth's stratosphere that contains a relatively high concentration of ozone (O₃) gas. Often described as Earth's "sunscreen," the ozone layer absorbs 97 to 99 percent of the Sun's medium-frequency ultraviolet light, which is harmful to life. Without the ozone layer, UV-B radiation would reach the Earth's surface in quantities sufficient to cause severe damage to living organisms, including increased rates of skin cancer, cataracts, and immune system suppression in humans, and reduced photosynthetic activity in phytoplankton—the foundation of the marine food web. Ozone is continuously created and destroyed in a natural balance known as the Chapman cycle. In this cycle, ultraviolet radiation strikes an oxygen molecule (O₂), splitting it into two individual oxygen atoms (O). Each free oxygen atom then combines with another O₂ molecule to form ozone (O₃). Ozone molecules are themselves broken down by UV radiation into an O₂ molecule and a free oxygen atom, releasing heat in the process. This continuous cycle maintains a relatively stable concentration of ozone in the stratosphere. However, in the 1970s, scientists discovered that certain human-made chemicals, particularly chlorofluorocarbons (CFCs), were disrupting this natural balance. CFCs are stable compounds that were widely used in refrigeration, air conditioning, foam production, and aerosol propellants. Because they are chemically inert and non-toxic, CFCs can persist in the lower atmosphere for decades and eventually diffuse upward into the stratosphere. There, intense UV radiation breaks them apart, releasing chlorine atoms. A single chlorine atom can catalytically destroy more than 100,000 ozone molecules before being removed from the stratosphere. This catalytic process led to the formation of an "ozone hole" over Antarctica, first documented in the mid-1980s. The Montreal Protocol, an international treaty signed in 1987, successfully phased out the production of CFCs and other ozone-depleting substances. As a result, the ozone layer is slowly recovering and is projected to return to pre-1980 levels by approximately 2060. According to the passage, why are CFCs particularly harmful to the ozone layer?