- In 1970, the world knew that UV rays caused cancer. But UV rays were mostly blocked by the ozone layer in the atmosphere.
- Paragraph 2 part one: Normally, the ozone layers is stable and unchanged. But two scientists showed that CFCs were destroying the ozone layer. CFCs came from manufactured products such as aerosols and refrigerants.
- Paragraph 2 part two: Freon CFCs break down in the upper atmosphere and release chlorine. Chlorine destroys ozone and regenerates itself in the process. A single chlorine molecule could destroy 100,000 ozone molecules.
- In 1974 the atmosphere contained five years worth of CFC production, which continued to cause damage. It would do so even if all CFCs stopped immediately.
- The two scientists had to overcome industry resistance, but in 1987 an international treaty banned CFCs. Now aerosols and refrigerants have more environmentally friendly chemicals.
This is a fact based passage. The overall structure and message is fairly clear compared to some other passages. Indeed, there is no main point question, a clear sign.
(I’d say the main point is: Mario Molina and F. Sherwood Rowland discovered that CFCs depleted the ozone layer. This led to a treaty banning CFCs.)
Since this is a fact based passage, your main task is figuring out what the passage is saying. Don’t let the scientific words scare you: the concepts here are fairly straightforward. This is a summary of what you need to know.
- Ozone lives in the upper atmosphere (“the stratosphere”). (lines 3-6)
- Ozone blocks UV rays. This is good, because UV rays help cause skin cancer. (lines 1-6)
- Normally, ozone gets destroyed and recreated in the upper atmosphere in equal amounts. It therefore stays constant over time. (Lines 11-14)
- CFCs rise to the upper atmosphere. There, they break down into parts, releasing chlorine. (Lines 21-33)
- Chlorine destroys ozone, and more chlorine is released in the process. (lines 29-31)
- So a single chlorine molecule can destroy 100,000 ozone molecules. (lines 31-33)
- Because it gets regenerated in the process, chlorine sticks around in the atmosphere for years, causing damage long after it was released. (lines 31-41)
- This damage weakens the ozone layer, letting UV radiation through. It even caused a “hole” in the ozone layer above Antarctica. (lines 52-53)
- CFCs used to be commonly used in air sprays and refrigerants. (lines 15-19)
- Molina and Rowland discovered that CFCs cause problems. (paragraph 2)
- After some initial resistance from industry, the scientists persuaded world governments to ban CFCs (paragraph 4)
- As a result, environmentally friendly CFC alternatives were developed. (lines 56-60)
That’s pretty much it. Chlorine isn’t necessarily the only thing that can damage ozone, but it’s the main cause in the passage that we know of.
If a word in the passage confuses you, read around it for context. The LSAT always defines the scientific terms it uses. And a lot of the details are not strictly necessary. Instead, you should try to to understand the main structural building blocks: points that build on each other in a logical way throughout the passage. These are the points I’ve identified.
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