Please choose the correct answer to the question: Which of the following is an example of a physical change but not a chemical change?

Answer1: A log gives off heat and light as it burns. Answer2: A tree stores energy from the Sun in its fruit. Answer3: A penny lost in the grass slowly changes color. Answer4: A water pipe freezes and cracks on a cold night.

Answer format: answer1/answer2/answer3/answer4
Answer: answer4