Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.
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Question: Question: What is the part of the shadow that is partially lit called? Answer: penumbra

Answer: The penumbra is the part of the shadow that is partially lit.

Question: Question: What causes blue litmus to turn red? Answer: acid

Answer: Acids change the color of certain acid-base indicators. Two common indicators are litmus and phenolphthalein. Blue litmus turns red in the presence of an acid, while phenolphthalein turns colorless.

Question: Question: Which law relates the pressure, volume, and temperature of a gas? Answer: combines gas law

Answer:
The combined gas law relates pressure, volume, and temperature of a gas.