Which of the following is a physical change? A newspaper burns when placed in a fire. An iron chair rusts when left outside. A sample of water boils and releases gas. A plant changes carbon dioxide and water into sugar. Question 3(Multiple Choice Worth 2 points) Which of these statements best describes the relationship between elements, compounds, and pure substances? Pure substances can be divided into two groups: elements and compounds. Compounds can be divided into two groups: pure substances and elements. Elements and pure substances are two of many different types of compounds. Pure substances and compounds are two of many different types of elements.