covalent molecule containing a dipole, example is water
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what is a dipole?
partial separation of charges; one atom is (+) and one is (-)
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what are hydrogen bonds?
weak bonds formed between molecules containing hydrogen, h must be attached to electronegative atoms (O,N,F)
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how are h bonds formed between water molecules?
positive h atom on one water molecule attracted to negative h atom on other water molecule
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what percentage of organisms is water?
60-70%
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why is water important in living organisms? (4)
-where biochemical reactions occur in cells as good solvent -carries substances as good solvent -ice less dense than water as water reaches maximum density at 4 degrees, will float and insulate -liquid so cannot be compressed
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why is water important in living organisms? (3)
-slow to absorb + release heat due to high specific heat capacity, no temp. change -cohesive (sticks together) for plant transport -adhesive (attracted to molecules) for plant transport and surface tension
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what is high surface tension and its advantages?
due to attraction between water molecules being more powerful than water molecules and the air, skin forms on masses of water. good for organisms on water and plant transport.
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what charge do protons have?
positive
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what charge do electrons have?
negative
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why are electrons in a water molecule held closer to oxygen atom?
oxygen atom more electronegative (better at attracting electrons because more protons in nucleus)
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why can sodium chloride dissolve in water?
attractive forces of positive sodium to negative polar region of water and negative chloride to positive polar region of water overwhelm forces between sodium chloride and ions dissociate to become solution
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what is nitrate(-) ion used for?
needed to produce amino acids
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what is phosphate(-) ion used for?
formation of ATP, ADP, DNA, RNA
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what is calcium(+) ion used for?
calcium pectate used for cell wall in plants, bone formation and muscle contraction in animals
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what is magnesium(+) ion used for?
needed to produce chlorophyll
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what is chloride(-) ion used for?
nerve impulses and secretory systems
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what is hydrogen(+) ion used for?
cellular respiration, photosynthesis, pH balance
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what is hydrogen carbonate or bicarbonate(-) ion used for?
buffers blood by neutralising acid to prevent it from becoming too acidic
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why is methane (CH⁴) non-polar?
symmetrical in structure so polarity cancels out; not enough partial charge
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how do electron shells affect bonding?
amount of electrons on outer shell affect bonding; more shells means harder to bond
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