Please choose the correct answer to the question: A teacher asks her students to examine titles of four scientific articles. Which titled article is specifically about a chemical change?

Answer1: How Baking Soda Reacts With Vinegar Answer2: How Rust Can Be Scraped off of Metal Answer3: How Metals Respond to Electrical Currents Answer4: How Elements Can Change Phase When Heated

Answer format: answer1/answer2/answer3/answer4