वह प्रक्रिया जिसके द्वारा कोई ठोस पदार्थ बिना तरल अवस्था से गुजरे सीधे गैस में बदल जाता है, कहलाती है:

Substances A and B together form C, and substances D and E together form F. The newly formed substances C and F have the following properties: (a) C exhibits the properties of both A and B. (b) D and E can be separated from F by electrochemical methods only. Which of the following statements is true?

Which of the following is considered a chemical change?