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All 12 Flashcards — Cohesion, adhesion and surface tension
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Question
Define cohesion.
Answer
The attraction of water molecules to **other water molecules** (water sticking to itself).
Question
Define adhesion.
Answer
The attraction of water molecules to a **different surface** (water sticking to something else).
Question
Define surface tension.
Answer
A 'skin-like' effect at the water surface, caused by **cohesion** pulling the surface molecules together.
Question
What causes cohesion and adhesion?
Answer
**Hydrogen bonding** between water molecules, which happens because water is **polar**.
Question
Which property lets a pond skater walk on water?
Answer
**Surface tension** (produced by **cohesion**).
Question
Water climbing the walls of a narrow xylem vessel is an example of…?
Answer
**Adhesion** — water sticking to a different surface.
Question
How does cohesion help transport in plants?
Answer
It holds water in an **unbroken column** in the xylem, so water can be pulled up from roots to leaves.
Question
How does adhesion help transport in plants?
Answer
Water sticks to the **walls** of the narrow xylem vessels, helping support and lift the water column.
Question
What is the cohesion–tension mechanism?
Answer
Cohesion + adhesion together let an unbroken water column be **pulled up the xylem** from roots to leaves.
Question
Cohesion or adhesion: water spreading out and wetting a leaf?
Answer
**Adhesion** — the water sticks to the leaf surface.
Question
Cohesion or adhesion: surface tension on a pond?
Answer
**Cohesion** — water molecules pulling on each other at the surface.
Question
Why is each hydrogen bond weak but water still cohesive?
Answer
Each bond is weak, but there are **so many** of them that together they hold the molecules tightly.
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Water
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