Nature’s Chemistry

Question 1

aldehyde

alkanal

Answer 1

• organic compound with carbonyl group (C=O) at the end of the structure
• oxidises to form a carboxylic acid
• reduces to form a primary alcohol

Question 2

ketone

alkanone

Answer 2

• organic compound with a carbonyl functional group (C=O) within the carbon chain / structure
• cannot be oxidised
• reduces to form a secondary alcohol

Question 3

condensation

reaction

Answer 3

reaction in which two molecules combine to form a larger molecule at the same time releasing a small molecule such as water

Question 4

hydrogenation

Answer 4

the addition of hydrogen to a carbon to carbon multiple bond

Question 5

hydrolysis

Answer 5

the breakdown of a molecule by the chemical action of water

Question 6

oxidation

Answer 6

• the loss of electrons in any reaction
• an increase in the oxygen to hydrogen ratio in a molecule

Question 7

polyunsaturated

Answer 7

molecule which has more than one carbon to carbon unsaturated bond

Question 8

reduction

Answer 8

• the gain of electrons in any reaction
• the decrease in oxygen to hydrogen ratio in a molecule

Question 9

unsaturated

Answer 9

• molecule with at least one carbon to carbon double bond
• test this by using bromine solution

Question 10

volatile

Answer 10

a substance which evapourates very easily to form gas

Question 11

homologous series

Answer 11

a family of compounds which have similar chemical properties and can be represented by a general formula

patterns in physical properties of the members of a series of often seen

Question 12

alcohols

Answer 12

• contain hydroxyl group (-OH)
• general formula: C_nH_2n+1OH

Question 13

diols

Answer 13

alcohols with two hydroxyl groups

Question 14

triols

Answer 14

alcohols with three hydroxyl groups

Question 15

primary alcohol

oxidation

Answer 15

alcohol –remove H–> aldehyde –add O–> carboxylic acid

Question 16

secondary alcohol

oxidation

Answer 16

alcohol –remove H–> ketone

Question 17

tertiary alcohol

oxidation

Answer 17

cannot undergo oxidation as there is no hydrogen atom bonded to the carbon atom attached to the hydroxyl group to be removed during oxidation

Question 18

identifying aldehydes and ketones

Answer 18

• mild oxidising agents can be used to distinguish one from the other
• acidified potassium dichromate (yellow/orange -> green)
• fehling’s solution (blue -> orange/red)
• tollen’s solution (clear -> mirror)

Question 19

carboxylic acid

Answer 19

• contains carboxyl group, -COOH
• names end in ‘-oic acid’
• general formula: C_nH_2n+1COOH

Question 20

ester

Answer 20

• contains ester link, -COO-
• used for food flavourings and perfumes

Question 21

making ester

reaction

Answer 21

• formed by a condensation reaction between alcohols and carboxylic acids
• carboxylic acid + alcohol –> ester + water

Question 22

making esters

experiment

Answer 22

• equal volumes of alcohol and carboxylic acid
• add sulfuric acid (catalyst)
• wrap weet paper towel round neck of test tube (condenser) and cotton wool plug
• sit in water bath (bunsen not used as conents are flammable) - leave for 30 mins
• add base to neutralise unreacted carboxylic acid and sulfuric acid
• immiscible layer should be present on surface, that is the ester

Question 23

breaking esters

Answer 23

• esters are split through a hydrolysis reaction
• ester + water –> carboxylic acid + alcohol

Question 24

fats and oils

formation

Answer 24

• natural esters so made by condensation reaction between glycerol (propane-1,2,3-triol - alcohol) and long chain fatty acids (carboxylic acids)
• glycerol + fatty acids <–> ester + water
• ratio of glycerol to fatty acid is 1:3 respectively

Question 25

fats | saturated fat - structure

Answer 25

- even structure allows close packing of molecules - closer means more LDFs - more LDFs makes them hard to break apart therefore they have high melting and boiling points hence saturated fats are solid

Question 26

oils | unsaturated fat - structure

Answer 26

- uneven, distorted structure means they are harder to pack together - this means less LDFs - less LDFs means they are easier to break apart therefore they have low melting and boiling points hence unsaturated oils are liquid

Question 27

oils --> fats

Answer 27

hydrogenation reaction turns oils into fats

Question 28

breaking fats and oil

Answer 28

hydrolysis breaks down fats and oils into their components (fatty acid and glycerol)

Question 29

soaps

Answer 29

- they are salts made from the alkaline hydrolysis of fats and oils - they consist of a long non-polar hydrophobic tail and an ionic head which is polar and hyrdophilic

Question 30

function of protiens

Answer 30

- major structural materials of animal tissue - maintenance and regulation of life processes

Question 31

naming esters

Answer 31

acid + alcolhol -> (alcohol)yl (acid)oate e.g. butanoic acid + methanol -> methyl butanoate

Question 32

emulsifier | purpose

Answer 32

to prevent non-polar and polar liquids separating into layers

Question 33

naming soaps

Answer 33

soaps are salts therefore name them like a salt from a neutralisation reaction

Question 34

emulsifiers | formation

Answer 34

- made by the partial hydrolysis of fats and oils - the hydroxyl groups are hydrophilic whereas the fatty acid chains are hydrphobic allowing them to hold together oil and water emulsions

Question 35

proteins | formation

Answer 35

condesation reaction between an amine group and carboxyl group to produce and amide link (peptide bond)

Question 36

bond rule in protein structure

Answer 36

bonds form from a hydrogen connected to an oxygen or nitrogen, to another oxygen or nitrogen

Question 37

antioxidants

Answer 37

- molecules that prevent food form spoiling quickly by preventing oxidation taking place - antioxidants are reducing agents | e.g. vitamin c (ascorbic acid)

Question 38

essential oils

Answer 38

concentrated extract of aroma compunds extracted from plants through steam distillation or solvent extraction

Question 39

isoprene

Answer 39

2-methylbuta-1,3-diene

Question 40

terpenes

Answer 40

- unsaturated hydrocarbons formed by joining together isoprene units - isoprene joins head to tail to form terpenes which can be cyclic or straight chain - once oxidised to form terpanoids they are resposible for flavours and aromas in plants

Question 41

free radicals

Answer 41

highly reactive atoms which have one unpaird electron

Question 42

free radical reaction stages | names only

Answer 42

- initiation - propagation - termination

Question 43

initiation | stage one - free radicals

Answer 43

UV light breaks covalent bond to form free radical(s)

Question 44

propagation | stage 2 - free radicals

Answer 44

highly reactive radicals can remove atoms from other molecules to re-establish covalent bonds which produces a new free radical

Question 45

termination | stage 3 - free radicals

Answer 45

the chain reaction will end when two radicals react together and no new radical is formed

Question 46

free radical scavengers

Answer 46

chemicals that react with and destroy free radicals to form a stable molecule which prevents a chain reaction from occuring | e.g. antioxidants