A lighter like the one shown below uses a substance called butane as its fuel. The butane can be burned to create a flame at the tip of the lighter. A teacher shows some of her students that the el inside the lighter's fuel tank is a liquid. But when she pushes the button that lets the fuel out of the lighter, they observe that it comes out as a gas. She and her students decide to investigate to discover what makes the butane change from a liquid to a gas. Which Step of an investigation would help them determine what causes the change of state?