instruction:
Given a scientific passage and an answer, generate a question for the given answer.
question:
Passage: Experiments are sometimes hard or even impossible to do. For example, a scientist who is studying an extinct animal cannot experiment with the animal because it no longer exists. The scientist must rely instead on evidence in the natural world, such as fossils that the extinct animal left behind. Answer: experiments
answer:
What can be hard or even impossible to perform in a scientific sense?

question:
Passage: Scientists may publish articles about their research in peer-reviewed science journals. Peer review means that the work is analyzed by peers, in other words, by other scientists. The articles are published only if the other scientists are convinced that the research is accurate and honest. Answer: peer review
answer:
What is the process where scientific articles are checked and analyzed by other scientists before publication?

question:
Passage: The temperature at which a substance boils and changes to a gas is called its boiling point. Boiling point is a physical property of matter. The boiling point of pure water is 100C. Other substances may have higher or lower boiling points. Several examples are listed in the Table below . Pure water is included in the table for comparison. Answer: boiling point
answer:
What is the term for when a substance boils and changes to gas?