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Hydrogen bonding in water

Water is the main component of plasma in blood.

The slight positive charge (S+) and negative (S-) charges in the water (H2O) molecule result in hydrogen bonding between molecules.

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Intermolecular bonding in liquid water

In liquid water, hydrogen bonding between the molecules is responsible for some of the physical properties of water. These include water's high boiling point and high surface tension.

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Adhesion and cohesion

Intermolecular forces between water molecules (H = white, O = red), i.e. cohesion, and between water and cellulose, i.e. adhesion, help water ascend through the xylem in plant stems.

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Water columns in xylem

Cohesion in water allows water columns to be drawn up through the xylem as water evaporates in transpiration.

Water columns have the equivalent tensile strength of steel. This helps explain how water can be drawn up to the tops of tall trees in a continuous stream.

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As water cools, the molecules slow down so that eventually they do not have enough energy to break their hydrogen bonds.

As the temperature of pure water at atmospheric pressure reaches 0 °C, the water becomes locked into a crystalline lattice. Hydrogen bonds keep the molecules spaced apart, so ice is about 10% less dense than liquid water at 4 °C. Ice floats on liquid water.

If ice sank, ponds, lakes and eventually even oceans on Earth would freeze solid, making aquatic life as we know it impossible.

If this were the case, during summer, only the upper few inches of temperate oceans would thaw.

Instead, when a deep body of water cools, the floating ice insulates the liquid water below, preventing it from freezing.

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