# What is meant by work done “expanding against atmosphere”?

In the book, Chemistry : A molecular approach, I came across this line:

Over here what does the author mean by work done by expanding against atmosphere?

With a similar line of reasoning, the atmosphere is exerting a pressure of one atmosphere trying to compress your gas down. That's a huge pressure (nearly $10^5$ pascals!) and the gas in question has expanded against it. The wording makes sense.