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?

Uranium has two naturally occurring isotopes. 238u has a natural abundance of 99.3% and 235u has an abundance of 0.7%. it is the rarer 235u that is needed for nuclear reactors. the isotopes are separated by forming uranium hexafluoride uf6, which is a gas, then allowing it to diffuse through a series of porous membranes. 235uf6 has a slightly larger rms speed than 238uf6 and diffuses slightly faster. many repetitions of this procedure gradually separate the two isotopes. what is the ratio of the rms speed of 235uf6 to that of 238uf6? express your answer to five significant figures.