Natures Chemistry

Question 1

What is an addition reaction?

Answer 1

When 2 molecules combine to form a single molecule?

Question 2

What is oxidation and reduction for carbon compounds?

Answer 2

> Oxidation is an increase in the oxygen to hydrogen ratio

>Reduction is a decrease in the oxygen to hydrogen ratio

Question 3

How are emulsifiers made and used in food?

Answer 3

They are made by reacting edible oils with glycerol.
in the molecules formed only 1 or 2 fatty acid groups are linked to each glycerol backbone. Hydroxyl group is hydrophilic, hydroxyl groups dissolve in water. Fatty acid chains are hydrophobic and dissolve in oil. hydroxyl groups dissolve in water. this forms a stable emulsion.

Question 4

What is an emulsion?

Answer 4

An emulsion contains small drops of one liquid dispersed in another liquid.

Question 5

What happens in a condensation reaction?

Answer 5

2 molecules are joined together with the elimination of a small molecule.
When an ester link is formed, the small molecule that is eliminated is water.

Question 6

How are esters formed?

Answer 6

They are formed by condensation reactions between an alcohol and a carboxylic acid.
alcohol + carboxylic acid = ester + water
this is known as esterification.

Question 7

What is an ester?

Answer 7

A molecule containing an ester link ( O=C-O)

Question 8

What does the oxidation of food cause?

Answer 8

The oxidation of edible oils gives foods a rancid flavour.

Oxygen from the air causes the oxidation of food.

Question 9

What bases can carboxylic acid react with to produce salt + water (+ co2) ?

Answer 9

a metal oxide + CA = a salt + h2o
a metal hydroxide + CA = a salt + h2o
a metal carbonate + CA = a salt + h2o + co2

Question 10

What does a COOH group on a molecule mean?

Answer 10

That it is a carboxylic acid.

The COOH group is called a carboxyl

Question 11

What does an OH group on a molecule mean?

Answer 11

That it is an alcohol.

an OH group is called a hydroxyl.

Question 12

What is an alcohol group containing 3 hydroxyl groups called?

Answer 12

Triol

Question 13

What is an emulsifier used for?

Answer 13

An emulsifier can e used to prevent non polar and polar liquids from separating into layers.
(think mayo)

Question 14

Describe how detergents work.

Answer 14

it has a non polar hydrophobic tail and a polar hydrophilic head.
It removes oil and grease in the same way as soap but doesn’t form scum when used in hard water.

Question 15

What is an alcohol containing 2 OH groups called?

Answer 15

Diol

Question 16

What are antioxidants and what do they do?

Answer 16

They are molecules that prevent unwanted oxidation reactions from occurring.
They are substances that are easily oxidised, and oxidise in place of the compounds they have been added to protect.

Question 17

What is the difference between primary, secondary and tertiary alcohols?

Answer 17

Primary: The carbon the OH group is attached to is only joined to 1 other carbon.
Secondary: Joined to 2 other carbons
Tertiary: Joined to 3 other carbons

Question 18

What is a fatty acid?

Answer 18

Fatty acids are saturated or unsaturated straight chain carboxylic acids containing even numbers of carbon atoms ranging from C4-C24 (Primarily C16 + C18)

Question 19

When are fats and oils produced?

Answer 19

When an alcohol and glycerol condense with a carboxylic acid (Fatty acid)
Glycerol (Propane 1,2,3 triol) is a tryhydric alcohol)

Question 20

Why are fats and oils needed in the body?

Answer 20

> Highly concentrated source of energy (more than carbohydrates)
Essential for transport of fat soluble vitamins

Question 21

What happens if an ester is hydrolysed?

Answer 21

An alcohol and carboxylic acid are produced

Question 22

Are many flavour and aroma molecules aldehydes or ketones?

Answer 22

Aldehydes

Question 23

Explain how soaps work.

Answer 23

Soap molecules have a Polar hydrophilic heads and a non polar hydrophobic tail. Soaps are ionic and water soluble.
Hydrophobic head is attracted to the water and the tail is attracted to the oil.
oil and grease are held inside a ball and suspended in water.

Question 24

How can you differentiate between an aldehyde and a ketone?

Answer 24

Aldehydes can be further oxidised to a carboxylic acid.
an aldehyde but not a ketone will cause:
>Blue Fehlings solution to form a brick red precipitate
>Colourless Tollens reagent to form a silver mirror
>Orange acidified dichromate to turn green

Question 25

What solutions are used to oxidise primary and secondary alcohols and what happens to them?

Answer 25

Hot copper (II) oxide or acidified dichromate (VI) solutions.
During reactions:
Black copper(II) oxide forms a brown solid
Orange dichromate turns green

Question 26

What do secondary alcohols oxidise to?

Answer 26

To Ketones

Question 27

What do Primary alcohols oxidise to?

Answer 27

Firstly aldehydes then carboxylic acids

Question 28

Why are Soaps used?

Answer 28

Soaps are used to remove non polar substances like oil and grease.

Question 29

What is hard water and what happens when soap is used in it?

Answer 29

Hard water is water containing high levels of dissolved metal ions.
When soap is used in hard water, an insoluble precipitate called scum is formed.

Question 30

How are soaps produced?

Answer 30

They are produced by the alkaline hydrolysis of edible fats and oils.

Question 31

How are edible fats and oils formed?

Answer 31

They are produced by the condensation of glycerol and 3 carboxylic acids.

Question 32

What are esters commonly used as?

Answer 32

Flavourings and Fragrances as many have a pleasant/fruity smell
They are also used as solvents for non polar compounds as they are non polar.

Question 33

Why do fats have a higher melting point than oil?

Answer 33

> oils have a higher degree of unsaturation
presence of double bonds in oils distorts long chains of atoms. So oils cant pack as closely together
Less LDF’s in oil molecules due to poor packing so it is easy to separate