Question

Cohesion, adhesion and surface tension of water give rise to a phenomenon termed

• A. Tensile strength
• B. Capillarity
• C. Cavitation
• D. Polarity

Hint:

Think of a thin straw. Water rises higher in a thinner straw because of capillarity.
In plants, the Cohesion-Tension theory explains how transpiration pull can move water over 100 meters high!

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question focuses on the physical properties of water molecules and how they interact to allow water to move through the narrow vessels of a plant's xylem.
Detailed Explanation:

• Physical Properties of Water:
Cohesion: Mutual attraction between water molecules (due to hydrogen bonding).
Adhesion: Attraction of water molecules to polar surfaces (like the tracheary elements of xylem).
Surface Tension: Water molecules are more attracted to each other in the liquid phase than to water in the gas phase.

• Phenomenon of Capillarity:
In plants, these three properties together provide water with high tensile strength (ability to resist pulling force) and high capillarity.
Capillarity is the physical phenomenon where a liquid rises in thin, narrow tubes.
Because xylem vessels and tracheids have very small diameters, these forces allow water to be pulled up to significant heights.

• Analyzing other options:
Tensile strength: A property provided by these forces, but not the term for the rising phenomenon itself.
Cavitation: The formation of air bubbles in the xylem, which breaks the water column (a failure of the system).
Polarity: A fundamental chemical property of the water molecule that causes cohesion and adhesion.

Step 2: Final Answer:
The phenomenon resulting from cohesion, adhesion, and surface tension that aids in the ascent of sap is capillarity.