system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When a container is sealed we call it 'airtight', is this the same as watertight or do liquids and gasses escape at different rates?
gpt
The molecules involved can be different sizes. An airtight object is water tight (assuming it doesn't fail). A watertight object is not necessarily air tight. A gap too small to let water in could potentially let air out. Some gasses can be even smaller. Helium balloons will actually leak helium through the skin of the balloon, for instance, over time.