Final answer:
When Potions, Inc. sold its patents for $10,000 with a book value of $9,000, it recorded a gain of $1,000, which represents the difference between the selling price and the book value of the patents.
Step-by-step explanation:
When Potions, Inc. sold its patents for $10,000, and the book value of these patents was $9,000, it will record a gain on the sale of $1,000. The gain will be recorded on the income statement as a non-operating income. This gain represents the difference between the selling price of the patents and their book value.