- Matter in the gas phase has variable volume
- Matter in the gas phase has variable shape
- So, matter in gas phase has variable volume and shape

- Matter in gas phase has variable volume and shape
- Matter with variable volume and shape expands to fill the shape and size of its entire container
- So, gas will expand to fill the shape of the container

- Gas will expand to fill the shape of the container
- Air is a kind of gas
- So, air will expand to fill the shape of the container

Hence, air will expand to fill the shape of the container
Q: Four materials are put into small containers. These materials are then moved from the small containers into larger containers. Which material will spread out to completely fill a larger container?
Context:
- Matter in the gas phase has variable volume 
- Matter in the gas phase has variable shape 
- Matter with variable volume and shape expands to fill the shape and size of its entire container 
- Air is a kind of gas