Every lesson in this course has something on a kitchen counter. Here is a tour, with the lesson each idea comes from.
| In the kitchen | The chemistry | Lesson |
|---|---|---|
| fruit bowl | ripening fruit gives off ethene | 2 |
| tap water | bent, with a δ− oxygen and δ+ hydrogens | 3, 11 |
| kitchen blowtorch | butane, a chain of four carbons | 4 |
| bananas | isoamyl acetate, an ester | 5 |
| vinegar | ethanoic acid gives away H⁺ | 5, 13 |
| vanilla, cinnamon | molecules built on a benzene ring | 6 |
| spearmint, caraway | the two hands of carvone | 7 |
| gas stove | methane burns to carbon dioxide and water | 8, 18 |
| freezer bags | long chains of poly(ethene) | 9 |
| butter, olive oil | straight and kinked fat chains | 10 |
| sugar in tea | hydrogen bonds with water | 12 |
| baking soda | a base that fizzes with acid | 13 |
| washing-up liquid | two-ended molecules lift grease | 14 |
| carrots, red cabbage | runs of alternating double bonds | 15 |
| fridge | cold slows the reactions that spoil food | 16 |
| cooking oil left open | oxygen turns fats rancid | 17 |
| medicine cupboard | aspirin, from willow bark | 19 |
Underneath all of them is lesson 1: a carbon atom with four hands, joining to other atoms and to other carbons in chains, rings and branches.
Mayonnaise
Oil and water separate, as you have seen. Whisk oil drop by drop into egg yolk and lemon juice, and the oil breaks into tiny droplets that stay spread through the watery juice: that is mayonnaise. A mixture of droplets of one liquid held in another is called an emulsion. Milk is one too, with droplets of fat in water.
The droplets stay apart because egg yolk holds lecithin, a two-ended molecule like the soap that lifts grease. It is built like a fat molecule: glycerol with two fatty acid chains on it, and in place of the third chain, a head that carries a positive and a negative charge. The head stays in the water and the two oily tails push into the oil, so lecithin coats every droplet and keeps them from joining up.
Quick check
That's the end of lesson 20
In this lesson you found out:
- What happens when sugar turns to caramel
- Why toast and seared meat turn brown and taste richer
- Why an egg sets when you cook it
- How the ideas from the whole course meet in the kitchen