skincare

Question 1

what does ultraviolet light do to human skin?

Answer 1

as it can provide sufficient energy to break bonds within molecule, it causes sunburn and accelerates the ageing of the skin.

Question 2

what happens when the uv light breaks bonds?

Answer 2

each atom takes an electron from the covalent bond producing atoms or groups of atoms with an unpaired electron- free radicals. the unpaired electron on each free radical makes it very reactive.

Question 3

what are the three stages of a free radical chain reaction?

Answer 3

1. initiation
2. propagation
3. termination

Question 4

what occurs during the initiation stage of a free radical chain reaction?

Answer 4

the uv light causes the atom to undergo homolytic fission producing a free radical.

Question 5

what occurs during the propagation stage of a free radical chain reaction?

Answer 5

the highly reactive free radical collides with a neutral molecule to produce a product molecule and another free radical, thus sustaining the reaction.

Question 6

what occurs during the termination stage of a free radical chain reaction?

Answer 6

the free radicals collide with each other producing neutral molecules. since another free radical is not produced the reaction stops.

Question 7

how to tell in an exam question which stage it is?

Answer 7

electrons will be represented by dots. if there is a dot on the right side, it is initiation, dots on both sides means propagation, dots on the left side means termination.

Question 8

what are free radical scavengers?

Answer 8

molecules that react with free radicals to form stable molecules.

Question 9

what are free radical scavengers used for ?

Answer 9

added to products involving cosmetics, food products and plastics.