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level: Skincare

Questions and Answers List

level questions: Skincare

QuestionAnswer
what is ultraviolet lighta high energy form of light present in sunlight
what can ultraviolet light provide enough energy to do to bonds within moleculescan provide enough energy to break bonds within molecules
what is the effect of ultraviolet light on our skinit can cause sunburn and accelerate ageing of the skin
what does sunblock do to UV lightit contains compounds that reflect the UV so that it does not reach the skin at all (this is not the same as sunscreen)
what are free radicalsatoms that are highly reactive due to the presence of an unpaired electron
how are free radicals formedwhen UV light breaks covalent bonds, leaving two atoms with unpaired electron
what is a substitution reactiona reaction involving free radicals eg. CH4 + Cl2 → CH3Cl + HCl it is known as substituion as one of the H atoms in methane is substituted for a Cl atom
what are the three steps to a free radical reactioninitiation propagation termination
describe the initiation stage of a free radical reaction involving methane and chlorineUV light is shone on a mixture of methane and chlorine there is enough energy in the UV light to break the Cl-Cl bond to produce to Cl atoms Cl-Cl→Cl˙+Cl˙
what is meant by the notation Cl˙chlorine radical
describe the propagation step of a free radical reaction involving chlorine and methanehighly reactive chlorine radical react with methane molecules this produces methyl radicals which then react with chlorine molecules (Cl2) Cl˙ + CH4 →CH3˙+ HCl CH3˙ + Cl2 → CH3Cl + Cl˙
describe the termination step of a free radical reaction involving methane and chlorinetwo free radicals combine to form stable molecules Cl˙ + Cl˙ → Cl2 CH3˙ + CH3˙ → C2H6 CH3˙ + Cl˙ → CH3Cl
when writing the steps for a free radical reaction between a hydrocarbon and a halogen, what does the initiation step always involvethe halogen molecule breaking up to form two halogen radicals
what are free radical scavengerscompounds that combine with free radicals to form stable molecules and prevent chain reactions from occuring
where are free radical scavengers addedproducts including cosmetics, food products and plastics