NATS 1870 Lecture 11: SC NATS 1870 LECTURE 11
12 Aug 2016
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Document Summary
Colour as an information giver: colour can be a temperature indicator (not chemistry, can indicate ph level (acidity) in a solution, fruit ripens, fruit goes bad, metals can oxidize. Colour change as information: acidity, levels of oxidation, food cooking changes colours, change of seasons (leaves change colour) Colour change can be a visible probe of change at the microscopic level: chemical reactions can happen, new molecules can be created = visible colour change, molecules can have their structure change = visible colour change. Key for colour: the way a molecule it put together, spacing of energy levels ( structure, bonds determine spacing of energy levels/ orbits) Types of bonds: ionic-> one atom donates e- to neighbour. Need uv photo to raise e- to higher level. Tuesday, november 3, 2015: covalent bonds-> equally shared. These bonds tend to be present in colorants (dyes, pigments) There is a range of rotational+vibrational energies within each (electronic) energy level.
