Water (2.1.1)

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What is a hydrogen bond?
Weak interaction that can occur where molecules contain a slightly negatively charged atom bonded to a slightly positively charged hydrogen.
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Describe the structure of water.
2 hydrogen atoms are covalently bonded to an oxygen atom. The larger oxygen molecule pulls the shared pair of electrons towards it, so the water has an uneven charge distribution across it and is a polar molecule.
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How is the evaporation of water into its gaseous form useful for organisms?
It uses up a large amount of energy to convert water in sweat into a vapour. This means that heat energy is lost in sweating, giving a cooling effect.
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Why is water a good transport medium?
It remains a liquid over a large temperature range.
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What does water do in animals?
Makes up the bulk of blood plasma.
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What does water do in plants?
Carries mineral ions up the plant from the soil through the xylem tissue.
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Why is ice being less dense than water useful to aquatic organisms?
Ice on the surface of a pond or lake insulates the water below. This allows organisms to survive the harsh winter conditions, if they stay below the ice.
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How is ice formed?
As temperature is reduced, water molecules move less because they have less k.e. This means more hydrogen bonds form. The water becomes a solid, semi-crystalline structure.
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Why are cohesion and surface tension useful to living organisms?
Cohesion is useful in enabling large columns of water to move up the xylem. Surface tension is useful for some small insects that travel on the water.
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How do molecules dissolve in water?
The POLAR substance to be dissolved has slightly negative & positive parts that can interact with the slightly charged parts of the water molecule. Water molecules cluster around solute molecules, keeping the solute molecules separate from each other
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Why do ions dissolve readily in water?
Because they are charged.
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Card 2

Front

Describe the structure of water.

Back

2 hydrogen atoms are covalently bonded to an oxygen atom. The larger oxygen molecule pulls the shared pair of electrons towards it, so the water has an uneven charge distribution across it and is a polar molecule.

Card 3

Front

How is the evaporation of water into its gaseous form useful for organisms?

Back

Preview of the front of card 3

Card 4

Front

Why is water a good transport medium?

Back

Preview of the front of card 4

Card 5

Front

What does water do in animals?

Back

Preview of the front of card 5
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