# Stopper

Use stoppers to stop gases escaping from Flasks and Test tubes. Stoppers can also be connected to rubber tubes to control the flow of gases between vessels.

To add a stopper to a vessel:

1. Move the stopper close to the neck of your chosen vessel.
2. Release the mouse button.
3. If the stopper is close enough to the vessel neck, it will snap into it automatically.

Tips for use:

- If a vessel closed by a stopper experiences a rise in pressure, the stopper will pop out.
- You can adjust the length of the glass tubes in the One tube and Two tube stoppers by using the control on their lower ends.

## See also:

- Flask
- Rubber tube
- Using chemistry parts