nature's chemistry

Question 1

saturated vs unsaturated

Answer 1

saturated compounds only contain C-C single bonds, unsaturated compounds contain at least one C-C double bond.

Question 2

how do you test for unsaturation?

Answer 2

add bromine water, if the compound is unsaturated then it will quickly decolourise

Question 3

what is an isomer?

Answer 3

compounds with the same molecular formula but different structural formulas

Question 4

what is the functional group in alcohols called?

Answer 4

hydroxyl (OH)

Question 5

primary, secondary and tertiary alcohols

Answer 5

primary: carbon attached to the functional group is only attached to one other carbon
secondary: carbon attached to the functional group is attached to two other carbons
tertiary: carbon attached to the functional group is attached to three other carbons

Question 6

diols and triols

Answer 6

diol: alcohols with two OH groups
triol: alcohols with three OH groups

Question 7

how does number of hydroxyl groups affect the alcohols?

Answer 7

more hydroxyl groups will result in a higher melting and boiling point due to the greater degree of hydrogen bonding.

Question 8

what is the functional group in a carboxylic acid called?

Answer 8

carboxyl (COOH)

Question 9

reactions that carboxylic acids have

Answer 9

+ metal oxide = salt + water
+ metal hydroxide = salt + water
+ metal carbonate = salt + water + carbon dioxide

Question 10

ester link?

Answer 10

COO

Question 11

how are esters produced and named?

Answer 11

produced from an alcohol and carboxylic acid.
first part of the name comes from alcohol, the second from the carboxylic acid e.g. ethanol + propanoic acid = ethyl propanoate

Question 12

uses of esters

Answer 12

flavourings, fragrances, solvents

Question 13

reactions to form and break esters

Answer 13

condensation forms esters, hydrolysis breaks them

Question 14

what is a condensation reaction?

Answer 14

two molecules join together to form a bigger one, with the elimination of a small molecule, usually water.

Question 15

what is a hydrolysis reaction?

Answer 15

breaking of a large molecule by the addition of water.

Question 16

formation of edibles fats end oils

Answer 16

they’re formed from the condensation of glycerol with 3 fatty acid chains

Question 17

explain the difference in melting points of fats and oils

Answer 17

oils have a higher degree of unsaturation and therefore prevents the chains packing together closely, so there are fewer LDFs and therefore have a lower melting point

Question 18

why do we need fats and oils?

Answer 18

they’re a concentrated source of energy for us and are essential for the transport and storage of fat-soluble vitamins for our bodies

Question 19

formation of soaps

Answer 19

produced by alkaline hydrolysis of edible fats and oils, which produces 3 fatty acid molecules and glycerol. the fatty acid molecules are then neutralised by an alkali, forming ionic salts, which we call soaps.

Question 20

use of soaps

Answer 20

to remove non-polar substances like oil and grease

Question 21

action of soaps

Answer 21

hydrophilic polar head enters the water, leaving the hydrophobic non-polar tail in the oil/grease. agitation of the mixture causes small ball-like structures form, and the negatively charged heads repel each other, preventing them from combining. this allows the oil/grease to be removed

Question 22

hard water

Answer 22

water containing high levels of dissolved metal ions.
scum (insoluble precipitate) is commonly found in areas with hard water.

Question 23

detergents

Answer 23

do not form scum with hard water

Question 24

what do emulsifiers do?

Answer 24

prevent polar and non-polar substances from separating into layers

Question 25

structure of emulsifiers

Answer 25

one or two fatty acid chains attached to glycerol

Question 26

how emulsifiers work

Answer 26

there are spare hydroxyl groups, which means there is a non-polar, hydrophobic part which can dissolve in oil/grease, and a polar, hydrophilic part which can dissolve in water

Question 27

role of proteins

Answer 27

major structural materials of animal tissues, essential for the maintenance and regulation of life processes

Question 28

what are proteins made from?

Answer 28

amino acids

Question 29

groups in an amino acid

Answer 29

an amino group (NH2) and a carboxyl group (COOH)

Question 30

how are proteins formed?

Answer 30

the amino group on one amino acid and the carboxyl group of another join together, with the elimination of water (condensation reaction)

Question 31

peptide link

Answer 31

CONH

Question 32

essential amino acids

Answer 32

required by the body but have to obtained through the diet

Question 33

what happens to proteins during digestion?

Answer 33

they're broken down via enzyme hydrolysis

Question 34

protein shape

Answer 34

can form spirals, sheets, and other complex shapes. they are kept in these shapes by intermolecular (hydrogen) bonding

Question 35

what happens to proteins when they're heated?

Answer 35

intermolecular bonds are broken which denatures the protein, which causes the texture of food to change

Question 36

oxidation (ratio)

Answer 36

increases oxygen to hydrogen ratio

Question 37

reduction (ratio)

Answer 37

reduces oxygen to hydrogen ratio

Question 38

oxidation of alcohols

Answer 38

primary alcohol - aldehyde - carboxylic acid secondary alcohol - ketones cannot be oxidised tertiary alcohols cannot be oxidised

Question 39

oxidising agents + colour changes

Answer 39

- hot copper oxide (black to brown) - acidified dichromate solution (orange to green) - Fehling's solution (blue to brick red) - Tollen's reagent (forms silver mirror)

Question 40

what can oxidising agents be used to identify?

Answer 40

aldehydes (not ketones)

Question 41

why can't tertiary alcohols be oxidised?

Answer 41

branch attched to carbon attached to hydroxyl group means =O can't be formed

Question 42

aldehydes vs ketones

Answer 42

both have carbonyl groups (=O), but aldehyes have it on the end of the molecule, ketones have it in the middle

Question 43

uses of aldehydes

Answer 43

have distinct flavours and aromas so are used in food products or essential oils

Question 44

what happens when food reacts with oxygen?

Answer 44

oxygen from the air reacts with edible oils, giving them a rancid flavour

Question 45

antioxidants

Answer 45

molecules that prevent unwanted oxidation from occurring by being oxidised in their place (they are reducing agents)

Question 46

essential oils

Answer 46

concentrated extracts of volatile, non-water soluble aroma compounds which come from plants. used in perfumes, cosmetic products, flavourings, and cleaning products

Question 47

what are terpenes made from?

Answer 47

isoprene units bonding together

Question 48

effect of UV light on the body

Answer 48

breaks bonds, causing sunburn, ageing, and cancer

Question 49

what is a free radical

Answer 49

atom/molecule that is highly reactive as it has an unpaired electron

Question 50

steps in a chain reaction

Answer 50

1. initiation (free radicals on right) 2. propagation (free radicals on both sides 3. termination (free radicals on left)

Question 51

free radical scavengers

Answer 51

molecules that react with free radicals to form stable molecules to prevent any unwanted chain reactions from occurring.