Heat caused an increase in gas production. Heat caused a new substance to form. Heat caused a decrease in energy. Heat caused a change in state.
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: When frozen carbon dioxide (CO_{2}) is heated, it changes directly into a gas. Which statement best indicates that a physical change has taken place?
Possibilities:
- Heat caused an increase in gas production.
- Heat caused a new substance to form.
- Heat caused a decrease in energy.
- Heat caused a change in state.

Heat caused a change in state.