Water has strong cohesion between water molecules; this supports columns of water in tube-like transport cells of plants and produces surface tension where water meets air
Water molecules attract each other strongly. This attraction holds water together in long columns inside plants and creates a tight "skin" where water meets air.
Real World
Transpiration in a 30-metre-tall oak tree pulls unbroken columns of water from roots to leaves against gravity — possible only because hydrogen bonding between water molecules gives them the cohesive strength to avoid breaking under tension.
Exam Focus
Distinguish cohesion (water–water) from adhesion (water–cell wall) — both contribute to transport, and confusing them costs marks.
Evaluation Scaffold
A four-step framework for high-quality evaluation. Use this for 'assess', 'evaluate', and 'to what extent' questions.
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