Take an bottle with a narrow opening that had your favorite beverage in it, and when it is empty blow across the top of the bottle. Now add some water so that the bottom of the bottle is covered and the air space is less with the bottle still vertical. Blow on that across the top. Does the pitch (frequency) of the resonant sound increase or decrease? You can try it yourself, and then explain what you found.

Take an bottle with a narrow opening that had your favorite beverage in it, and when it is empty blow across the top of the bottle. Now add some water so that the bottom of the bottle is covered and the air space is less with the bottle still vertical. Blow on that across the top. Does the pitch (frequency) of the resonant sound increase or decrease? You can try it yourself, and then explain what you found.