Biology SL Chapter 3.1 Chemical elements and water

The most frequently occuring elements (CHON)

Carbon, Hydrogen, Oxygen, Nitrogen

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Other frequently occurring elements (SCIPS)

Sulphur, Calcium, Iron, Phosphorus, Sodium

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One role for sulphur, calcium, iron, phosphorus and sodium

Sulphur: Found in certain amino acids, allows proteins to for disulphide bonds. calcium: Bone growth and teeth. Iron:haemoglobin for O2 transport . Phosphorus:component in nucleic acid and cell membranes. Sodium:Generation of nerve impulses

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Structure of water molecule

H2O is made up of 2 H atoms covalently bound to an O atom.The oxygen atom, having more protons (+ve), attract the electrons (-ve) more strongly. Thus the oxygen atom becomes slightly negative and the hydrogen atoms become slightly positive

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Four properties of water

Thermal, Cohesive, solvent, transparency,

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Thermal properties of water

Water has high specific heat capacity(energy needed to raise it 1deg C), heat vaporisation(energy needed for 1g to vaporise) and fusion (energy needed for 1g to freeze). Occurs due to hydrogen bonding between H2O molecules.

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Cohesive properties of water

Water molecules are cohesive (stick together). Will also stick to other charged or polar molecules (adhesion). Happens due to polarity of water molecule

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Solvent properties of water

Water can dissolve many organic and inorganic substances that contain electronegative atoms. This occurs because polar attraction of large quantities of H2O molecules can weaken intra-molecular forces (such as ionic bonds)which dislocate atoms.

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Relationship between properties of water (and its use as a coolant)

Both plants and animals use evaporation of water to facilitate cooling (sweating/transpiration). Water can also be used to carry heat to cooler places in our bodies.

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Relationship between properties of water (and as a medium for metabolic reactions)

Water can dissolve many organic and inorganic substances to facilitate chemical reactions. Water can also absorb thermal energy as a by-product of many chemical reactions

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Relationship between properties of water (as a transport medium)

The attraction between water molecules facilitates its transport up xylem of plants. Water can be an effective transport medium for dissolves substances. Water in blood is used to transport oxygen, glucose and urea.

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Biology SL Chapter 3.1 Chemical elements and water

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