The air in a scuba tank is composed of approximately 78% nitrogen, 21% oxygen, with the remainder being a mix of argon, carbon dioxide, neon, helium and others.

Writing, you can revisit previous parts of the lesson by returning to the course map. be sure to refer to the lab’s student guide, which you can find on the first page of the lab experiment activity

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By water evaporation from the leaves is created a negative pressure at the top of the tree that promotes the ascension  of the water through channels that are called xylem. there are also two molecule forces that are involved: the intra-water molecules cohesion (water molecules stick to each other) and the adhesion when the water molecules stick to the channels they are running in. this is what enables water to go from the roots to the top of a tall tree.