Nature's Chemistry Flashcards
1
Q
Polarity of hydrocarbons
A
Non polar
2
Q
What is organic chemistry?
A
Basically the study’s of compounds containing carbon (with the exclusion of oxides and carbonates)
3
Q
What are the names and chemical formulas for the first 8 alkanes?
A
Methane - CH4
Ethane - C2H6
Propane - C3H8
Butane - C4H10
Pentane - C5H12
Hexane - C6H14
Heptane - C7H16
Octane - C8H18
4
Q
What’s the general formula for the alkane series?
A
CnH2n+2
5
Q
What’s an isomer?
A
Molecules that have the same chemical formula but different structures
6
Q
What’s an alcohol?
A
A carbon compound that contains the hydroxyl functional group (OH)
7
Q
Names and formulas for the first 8 alcohols
A
Methanol - CH3OH
Ethanol - C2H5OH
Propanol - C3H7OH
Butanol - C4H9OH
Pentanol - C5H11OH
Hexanol - C6H13OH
Heptanol - C7H15OH
Octanol - C8H17OH
8
Q
General formula for the alcohols
A
CnH2n+1OH
9
Q
What is an organic compound?
A
Compound which molecules contain chains of carbon atoms
10
Q
Describe the flame produced when ethanol burns
A
- light blue
- v flammable
- no smoke
11
Q
Why is ethanol not ionic?
A
It does not conduct electricity when molten or dissolved in solution
12
Q
What functional group is found in carboxylic acids?
A
Carboxyl
13
Q
What is methanoic acid also known as?
A
Formic acid
14
Q
Where is methanoic acid found?
A
Ant stings and bee venom
15
Q
Where is ethanoic acid found and used in?
A
- vinegar
* in the production of plastic and pharmaceuticals
16
Q
What is ethanoic acid also known as?
A
Acetic acid
17
Q
Dehydration and hydration result in ____ molecule
A
Still one
18
Q
Condensation results in ___ _____ molecules
A
Two separate
19
Q
When are esters made?
A
When an alcohol and carboxylic acid react together
20
Q
What would form when ethanol and ethanoic acid react?
A
The ester ethyl ethanoate
+
Water
21
Q
What by product is formed in an ester reaction?
A
Water
22
Q
What type of chemical is taking place when an ester is formed?
A
Condensation reaction
23
Q
What’s the ester link?
A
The link formed between the carboxyl and hydroxyl groups once water is removed
24
Q
Explain what the most suitable method of hearing should be used in the making esters reaction
A
Water bath - chemicals v flammable so not a gd idea to burn over Bunsen
25
What’s the catalyst in the making esters reaction?
* concentrated sulphuric acid
* specifically the H+ ions
* help remove water
26
What’s the purpose of the paper towel soaked in cold water in the making esters reaction?
- wet paper = condenser
| - cools down the evaporating has so it turns back into liquid and drops back into the boiling tube so none is lost
27
What’s the purpose of the ceramic wool plug in the making esters reaction?
* stop fumes/ester/ acid/alcohol escaping
| * safety
28
Esters can be split by a ____ reaction to form an alcohol and a _____ ___
Hydrolysis
Carboxylic acid
29
How is hydrolysis usually carried out?
By heating in the presence of a dilute acid.
The hydrogen ions catalyse the hydrolysis
Reversible
30
How can you increase the yield of an ester?/ complete hydrolysis of esters?
If the ester is added to a strong alkali eg NaOH and heated under reflux the process can be completed.
ALKALINE HYDROLYSIS
Not reversible
31
What is produced from the complete hydrolysis of esters?
The alcohol and salt of the carboxylic acid
32
How can the products of ester hydrolysis be separated?
Through distillation.
The alcohol will be distilled off and the salt of the acid will be left in the flask.
The salt solution can then be acidified with HCl and the salt is converted to carboxylic acid.
33
Ester uses?
* fragrances
* flavourings
* aspirin (is an ester)
* nail polish/ paint (solvents)
34
How do esters work as solvents in paint and nail polish?
Keeps liquid and then evaporated out and leaves dry coloured compounds
35
What medicine is an ester?
Aspirin
36
What are fats?
Esters formed from 1 molecule of glycerol and 3 molecules of (usually saturated) long chain carboxylic acids
37
Are fats saturated or unsaturated?
Saturated
38
Fats have melting points ___ enough to be ___ at room temperature
High
Solid
39
What are oils?
Esters formed from one molecule of glycerol and three molecules of (usually unsaturated) carboxylic acids.
40
Are oils saturated or unsaturated?
Unsaturated
41
Oils have melting points ___ enough to be ____ at room temperatures
Low
Liquids
42
Fats and oils provide a high source of ___ and help make you feel ___ for longer
Energy
Fuller
43
What are fats and oils source of?
Fat soluble minerals and essential fatty acids
44
Sources of fats and oils?
Veg - Olive oil, rapeseed oil
Animal - lard
Marine - cod liver oil
45
Fats and oils provide essential ___ and ___ acids
Vitamins
Fatty
46
How is vitamin D produced?
By our skin when exposed to sunlight
47
How must us Scots get vitamin D?
Rely on consuming foods such as fish, eggs, milk and meat as these contain fats and oils which store vitamin D
48
How can a vitamin D deficiency affect you?
Affect mental health
49
What has caused the increased popularity and use of rapeseed?
Used for cooking and producing biodiesel
50
Under cold conditions what happens to some vegetable oils?
Become cloudy and begin to solidify
51
How are fats and oils formed?
By a condensation reaction between glycerol with carboxylic acid molecules
52
Chemical name for glycerol?
Propan-1,2,3-triol
53
Glycerol is a tri_____
Triglyceride
54
What shape do fats and oils form?
A tuning fork shape with the limbs of 3 hydrocarbon chains
_________
|
—-——|
|_________
55
What holds fat/oil molecules together?
London Dispersion Forces
56
When the fat is heated the Van der Waal’s attractions are easily ____ causing the fat to ___
Broken
Melt
57
What’s hardening?
The process of hydrogenating an oil to produce a more solid compound
58
What’s hydrogenation?
The addition of hydrogen to an unsaturated compound eg hydrogenation converts alkenes to alkanes and oils to fats
59
How are oils converted to fats?
But the use of hydrogen
A nickel catalyst is used during this reaction
60
Fats and oils are ____ in water
Insoluble
61
We refer to fats and oils as h______
Hydrophobic
62
What does hydrophobic mean?
Molecules or parts of molecules which repel water and will not bond to water
63
Polarity of fats and oils?
Non polar
64
Why are fats and oils non polar?
They contain no polar OH groups or other ions that could bond to water
65
Vitamins can be ___ soluble or ___ soluble
Fat or water
66
What are soaps formed from?
Fats and oils by treating them with an alkali such as sodium or potassium hydroxide
This causes alkaline hydrolysis of the 3 ester links in the fat or oil
The products of this reaction are glycerol and the sodium or potassium salt of the acid.
This salt is ‘soap’
67
What is soap?
Salts of fatty acids.
Soaps have an ionic head that is water soluble and a covalent tail which is soluble in oil
68
Structure of soap?
1) an ionic head (carboxylate ion) which is water soluble
| 1) A covalent hydrocarbon tail which is soluble in oil/grease
69
The covalent tail of soap is a ___ ____ hydrocarbon chain: this causes is to bond easily to the ___ material on skin or fabric
Non polar
Greasy
70
The soap tail is _____ and therefore does not bond to ___
Hydrophobic
Water
71
The ionic head of soap is attracted to the polar covalent ___ molecules and is therefore _____
Water
Hydrophilic
72
What does the covalent tail bonding to grease and the ionic head bonding to water result in?
Globules of grease being dispersed in water
73
What’s ‘hard water’?
Contains dissolved calcium and magnesium ions
74
What does hard water form when it mixes with soap?
A precipitate rather than a soapy lather
75
What does the precipice formed from hard water leave?
A ‘scum’
76
What’s soapless detergent?
Has a soap like structure but will not form a precipitate when mixed with hard water
77
What’s an emulsion?
A mixture of liquids where small droplets of one liquid are dispersed in another liquid
Brings substances together/ Stops them separating out into layers
78
Example of an emulsion?
Grease particles mixed in soapy water
79
Example of emulsifiers in food?
Milk contains natural emulsifiers such as sodium caseinate and phospholipids which help the fatty components to disperse throughout the water in milk
80
What is a monoglyceride?
The structure has just one OH reacted with a fatty acid forming an ester. The other 2 remain free
81
How can a monoglyceride act as an emulsifier?
As the OH groups are polar allowing the fatty acid to dissolve in water, while the fatty acid is non polar allowing it to be soluble in oil
82
Why are proteins essential for human survival?
They provide the major structural material of animal tissue and play a big role in the maintenance and regulation of life
83
Example of a protein?
Enzymes
84
Proteins contain ____
Nitrogen
85
What will a protein break down into when hydrolysed?
Amino acids
86
What functional groups are found in amino acids?
Anime group
H2N
Carboxyl group
87
What happens when amino acids join together and what type of reaction is this?
The amino group joins with a hydroxyl group of another amino acid to form an amide link and a water molecule
This is a condensation reaction
88
Amide link structure?
O H
|| |
-C—N-
89
Amide links are also known as what?
Peptide links
90
The reaction for making proteins is usually referred to as what?
Condensation polymerisation
91
What can proteins be referred to as?
Polyamides
92
When does the breakdown of proteins occur?
During digestion
93
Describe the breakdown of proteins during digestion.
An enzyme hydrolysis reaction takes place, the peptide bond is broken by water molecules to produce amino acids
94
What are essential amino acids?
Amino acids which cannot be synthesised by the body and so must be consumed
95
Why are chemical reactions important in cooking?
So:
• the flavours in the raw food are not destroyed by the cooking process
* any flavours locked in the food are released when cooking
* the cooking process creates new compounds that add to the flavour of foods
96
Why do people with a blocked nose have a dampened sense of taste?
Tasting food involves smelling the flavour molecules as well
97
What is meant by a molecules volatility?
How easily it evaporates
98
Where is the flavour molecule limonene found?
Lemons and oranges
99
Capsaicin, the flavour of hot chilli peppers, is ____ in water
Insoluble
100
Why will drinking water not reduce burning in the mouth from a spicy meal?
Capsaicin is insoluble in water therefore it will not remove the molecule from your mouth
101
What should you drink to reduce burning from a spicy meal?
Milk - contains proteins which can act as emulsifiers
This will help the capsaicin mix with water and be removed from your mouth where it is making the nerves tingle
102
If the molecular mass is under ___ they are volatile and larger molecules over ___ are less likely to be volatile
300
103
Why is undecanal more volatile than citronellol?
Unlike citronellol it does not have an OH group and cannot form hydrogen bonds therefore it’s intermolecular bonds are much weaker causing it to be more volatile
104
Asparagus cooking tips?
* flavour molecules in asparagus are water soluble
| * therefore steaming or boiling asparagus in water is not recommended
105
Broccoli cooking tips?
* broccoli contains flavour molecules that are oil soluble
| * therefore to prevent the flavour escaping it is better to cook broccoli by steaming or boiling in water
106
Egg whites contain proteins; these proteins are able to ___ bond work themselves and the other protein molecules around them
Hydrogen
107
Why are egg white proteins able to hydrogen bond to themselves?
Bc of the polar C=O and N-H groups of the amide links
108
What are the two types of proteins?
* globular
| * fibrous
109
What’s the shape of an enzyme due to?
The folding and twisting of protein molecules
110
The proteins in egg whites are ____ proteins
Globular
111
What do the protein chains in egg whites do?
Wrap around each other and form a ball of molecules
The structure is held together by the hydrogen bonds
112
What happens to the hydrogen bonds between proteins in egg whites when we cook them?
Heat energy breaks these hydrogen bonds between the protein chains causing them to unfold
113
What’s denaturing?
When the hydrogen bonds between protein chains break causing them to unfold
114
What is the protein collagen?
A thin film in meat which holds the layers of muscle together
115
What does collagen do?
Helps keep muscles attached together and to the bone
116
What causes collagens tough structure?
It has protein molecules which wrap around in spirals
117
What happens to collagen in meat when cooked and at what temperature?
When the meat is cooked the heat causes the proteins to unwind which changes the shape and makes the molecule less tough
Meats must be heated to above 60*C for this change to occur
118
What gas is used in food packaging?
An inert gas (commonly nitrogen)
119
Why is food not packaged in air?
As aid contains moisture and oxygen that can spoil the food
120
Why is nitrogen used in food packaging?
It will not react with the food
121
What happens when food is exposed to oxygen?
It will begin to oxidise and become spoiled
122
How can you tell an apple has oxidised?
If you cut it and the skin turns brown
123
What’s an oxidation reaction?
One in which one of the atoms of ions loses electrons
124
What are the three types of alcohol?
Primary
Secondary
Tertiary
125
Position of the OH group in primary alcohols?
Joined to the end of the carbon chain
126
Position of the OH group in secondary alcohols?
Joined to an intermediate carbon atom
127
Position of the OH group in tertiary alcohols?
Joined to an intermediate carbon atom which also has a branch attached
128
Which alcohols can undergo oxidation?
Primary and secondary
129
Example of an oxidising agent?
| Colour change?
Acidified potassium dichromate
From orange to blue-green
130
What are aldehydes?
• Carbon compounds which contain -CHO functional group
131
What are aldehydes formed by?
By the oxidation of primary alcohols
132
What do aldehydes oxidise to produce?
Carboxylic acids
133
What are ketones?
Carbon compounds which contain the carbonyl group (C=O)
134
What are ketones formed from?
The oxidation of secondary alcohols
135
Can ketones be oxidised?
They cannot be oxidised using mild oxidising agents
136
When naming branches aldehydes and ketones what takes priority over the position of a branch?
The position of a functional group
137
What do the names of aldehydes end in?
-anal
hehehehhe
138
What do the names of ketones end in?
-one
139
Example of an oxidising agent for an aldehyde?
Colour change?
Tollens’ reagent
Colourless —> silver
140
What is an acid which ionises completely in water known as?
A strong acid
Eg
HCl(aq) —> H+(aq) + Cl-(aq)
141
Why are carboxylic acids known as ‘weak’ acids?
They will partially ionise when added to water
142
What do carboxylic acids produce when reacted with bases? (Metal carbonates etc)
Salts containing the carboxylate ion (COO-)
143
What would ethanoic acid and sodium hydroxide react to produce?
Sodium ethanoate and water
144
What are the salts of carboxylic acids commonly used as?
Preservatives in the food industry
Eg calcium propanoate prevents the growth of moulds which would spoil food
Sodium benzoate is added to soft drinks
145
Carboxylic acids can be ____ to form aldehydes and alcohols
Reduced
146
Oxidation of an alkanol or alkanal results in an ___ in the oxygen:hydrogen ratio
Increase
147
A reduction would ____ the oxygen:hydrogen ratio in alkanols or alkanals
Decrease
148
Oxidation occurs when there is an ____ in the oxygen to hydrogen ratio
Increase
149
Reduction occurs when there is a ____ in the oxygen to hydrogen ratio
Decrease
150
Example of a flavour molecule aldehyde
Cinnamaldehyde in cinnamon
151
What can be added to a food to prevent it spoiling once the packaging is opened?
An antioxidant
152
What’s a common antioxidant?
Absorbic acid (Vitamin C)
153
How do antioxidants work?
They readily undergo oxidation and save the food from oxidising
