Biology OCR ZH notes - Module 2

Notes from the ZH website and not class or tutor notes

Describe the structure of a water molecule

Two hydrogen atoms share their electron with one oxygen atom creating covalent bonds, the shared electrons are pulled towards the oxygen atom due to the two lone pairs of electrons it has,

giving the oxygen atom a partial negative charge and the hydrogen atoms a partial positive charge resulting in a polar molecule due to the unequal sharing of electrons.

These partial charges then attract other water molecules allowing hydrogen bonds to form between the opposite partially charged atoms

What are three properties of water?

Strong Cohesion - the polar water molecules stick together due to the strong hydrogen bonds between them. Water flows well e.g. it forms an unbroken column in xylem vessels. Water has a high surface tension and so it can form droplets which can support smaller organisms such as insects.

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