Final answer:
To determine which container holds the gas, Joan should look for the container with a larger volume relative to its mass, as gases are less dense and expand to fill their containers.
Step-by-step explanation:
To identify which container most likely contains the gas, we need to understand the properties of the three states of matter: solid, liquid, and gas. The key properties are: solids have a defined shape and volume, liquids have a fixed volume but take the shape of their container, and gases neither have a definite shape nor a specific volume, as they expand to fill their entire container.
When examining the mass and volume of Joan's four containers, the one that most likely contains the gas will be the container with a larger volume compared to its mass since gases tend to have lower densities than solids and liquids. Therefore, to identify the container with the gas, Joan should look for the container that seems lightest for its size, as this container's contents would have filled the entire volume available, indicative of a gas.