1. Higher Chemistry Skincare – Ageless Chemistry
REVISION
Alkanes
Hydrocarbons
Halogens
Antioxidants
NEW LEARNING
Formation of free radicals
Chain reaction mechanisms

2. Starter Task
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3. Starter Task
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4. Starter Task
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5. Lesson 1: Sunlight and Skin
Today we will learn to
Describe how UV radiation can break bonds to create free radicals.
We will do this by
Learning about UV light and its effects, then watching a video on the chemistry of how these effects are caused.
We will have succeeded if
Write chemical equations for initiation, propagation and termination stages of a free radical reaction.

6. Sunlight and Skin p37 Effect of Sunlight
Ultraviolet radiation (UV) is a high-energy form of light, present in sunlight. Exposure to UV light can result in molecules gaining sufficient energy for bonds to be broken. This is the process responsible for sunburn and also contributes to aging of the skin. Sun-block products prevent UV light reaching the skin.

7. Sunlight and Chemicals
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UV light is responsible for how the original photographs were developed. The first permanent photograph was an image produced in 1826 by the French inventor Joseph Nicéphore Niépce. His photographs were produced on a polished pewter plate covered with bitumen of Judea, which he then dissolved in white petroleum. Over the next few years the discovery that exposure to light caused silver halides to change colour led to a revolution in photographic technique.

8. Free radical reactions
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9. Free Radical Reactions
When UV light breaks bonds free radicals are formed.
Free radicals have unpaired electrons and, as a result, are highly reactive.
Free radical chain reactions include the following steps: initiation, propagation and termination.

10. Initiation U.V. light provides the energy for the homolytic fission of halogen into reactive halogen atoms or free radicals (atoms with an unpaired electron).

11. Propagation

12. Termination
In this stage, free radicals are used up by collision with each other.

13. Hangman You know what it is!
Pick a word from Unit 2 and using the whiteboards, see if your partner can guess it without hanging the man!

14. Lesson 2: Free Radical Scavengers
Today we will learn to
Explain how some molecules ‘mop up’ free radicals.
We will do this by
Watching a video of a steam distillation.
We will have succeeded if
We can explain how fragrance molecules like terpenes are obtained from natural sources.

15. Starter Task
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16. Starter Task
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17. Free Radical Scavengers
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18. Free Radical Scavengers
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19. Free Radical Scavengers
Many cosmetic products contain free radical scavengers. These are molecules which can react with free radicals to form stable molecules and prevent chain reactions.
Melatonin and Vitamin E are examples of natural free radical scavengers or antioxidants.
Free radical scavengers are also added to food products and to plastics.

20. ConsolidationTask Complete Quick Test 7. You have 10 minutes!
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21. Answers
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22. Past paper questions
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23. Past paper questions
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