Stephen shows us the mischevious nature of Liquid Nitrogen.
You will find out that nitrogen is a gas at room temperature, and that in order for it to be in a liquid state it must be very cold. When the nitrogen is cold enough to be a liquid, exposure to room temperature air will cause it to boil. As boiling nitrogen heats up and becomes a gas again, it expands. Therefore, if cold liquid nitrogren is placed in a sealed container at room temperature, the pressure from the gas's expansion will cause the container to explode.