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Z/ HIGHER Chemistry > Unit 2: Chapter 8 - Chemistry of Cooking and the Oxidation of Food > Flashcards

Unit 2: Chapter 8 - Chemistry of Cooking and the Oxidation of Food Flashcards

1
Q

What happens when you cook asparagus in water and why is this?

A

It loses its flavour as the flavour molecule is soluble in water.

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2
Q

What happens to broccoli if you cook it in water?

A

The broccoli retains it flavour as the flavour molecule is insoluble in water.

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3
Q

Why is vitamin C soluble in water?

A

It contain the hydroxyl group - OH.

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4
Q

What is volatility a measure of?

A

Ease of evaporation.

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5
Q

What does volatility depend on?

A
  • The size of the molecule and the London dispersion forces can have an influence where the larger the molecule the less volatile it is.
  • In general mass of below 300 are considered volatile.
  • A polar group within the molecule also has an influence on the volatility. Where intermolecular bonding can be more difficult to evaporate, decreasing volatility.
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6
Q

In the amide link what are the bonds?

A

Polar bonds between the Nitrogen to Hydrogen and Carbon and Oxygen.

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7
Q

What happens to the molecule and amide link when the protein molecule forms and what does this produce?

A

The molecule can curl in on itself allowing the amide links to align each other and hydrogen bonds with other amide links within the chain. This can produce a structure of protein called the alpha helix.

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8
Q

When is a β - pleated sheet formed and what happens when it is formed?

A

When more than one chain is present we see the hydrogen bonding cross linking between the chain forms a protein called the β - pleated sheet. As the protein builds up it takes on a flat almost 2 dimensional.

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9
Q

What are the two distinct groups that proteins fall into?

A

Fibrous and Globular.

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10
Q

What are fibrous proteins?

A

The major structural material in animal tissue, and are defined by their length being more than five times there width.

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11
Q

What are examples of fibrous proteins?

A

Examples of fibrous proteins are keratin found in horn, hoofs and hairs and collagen found in tendons and muscle protein.

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12
Q

What are globular proteins?

A

Globular proteins are involved in the maintenance and regulation of life processes.

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13
Q

What types of proteins do enzymes contain?

A

Globular proteins.

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14
Q

Why can an enzyme only catalyse a specific reaction?

A

The shape of the enzyme only allows a certain shape of reactant to combine with it. This is called the lock and key principal.

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15
Q

What happens when proteins are heated and what is this called?

A

The hydrogen bonding present breaks apart and can completely change the shape of a Alpha-helix or β - pleat protein. This is called denaturing the protein.

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16
Q

What happens enzyme catalysts are denatured?

A

Chemical reactions that occur in the body halt which can be lethal.

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17
Q

What does the denaturing of proteins in food cause?

A

The denaturing of proteins in foods causes the texture to change when it is cooked.

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18
Q

When food is spoiled what is said to have happened?

A

The food has been oxidised.

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19
Q

What is oxidation in carbon compounds?

A

Oxidation is an increase in the oxygen to hydrogen ratio.

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20
Q

What is reduction in carbon compounds?

A

Reduction is a decrease in the oxygen to hydrogen ratio

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21
Q

What is another name for an aldehyde?

A

An alkanal.

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22
Q

What is the functional group of the alkanals/aldehydes?

A

-CHO

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23
Q

What do all alkanals/aldehydes end in?

A

al.

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24
Q

What is the general formula of the alkanals/aldehydes?

A

CnH2nO

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25
Q

Where is the functional group -CHO in the alkanls/aldehydes and what does this mean for the naming of the alkanals/aldehydes ?

A

The functional group -CHO is always at the end and this means when naming alakanals/aldehydes we only have to consider the addition of ethyl and methyl groups.

26
Q

What is the functional group of the ketones/alkanones?

A

-CO-

27
Q

Where is the functional group -CO- always found in a ketone/alaknone molecule?

A

The -CO- is never at the end of the molecule and is always found within the molecule.

28
Q

What do all alkanones/ketones end in?

A

-one.

29
Q

What is the general formula of the alkanones/ketones?CnH2n0

A

CnH2n0

30
Q

What molecules do not exist in the ketones/alkanones and why is this?

A

Methanoate and Ethanoate as the group exists within the molecule.

31
Q

What is the functional group of the alcohols?

A

-OH

32
Q

What do all alcohols end in?

A

-ol

33
Q

What alcohol is commonly used in alcoholic drinks?

A

Ethanol

34
Q

What is the general formula of the alcohols?

A

CnH2n+1OH

35
Q

What are the 3 types of alcohols?

A

Primary, secondary and tertiary.

36
Q

What is the structure of a primary alcohol like?

A

The carbon the OH group is bonded to, is bonded t only ONE other carbon.

37
Q

What is the structure of a secondary alcohol like?

A

The carbon the OH group is bonded to, is bonded to TWO other carbons.

38
Q

What is the structure of a tertiary alcohol like?

A

The carbon the OH group is bonded to, is bonded to three carbons.

39
Q

When does oxidation occur?

A

When a substance gains oxygen.

40
Q

What is a way to check if oxidation has occurred?

A

Check the oxygen to hydrogen ratio between the reactant and the product.

41
Q

What can be used to oxidise alcohols?

A

Acidified potassium dichromate and hot copper (II).

42
Q

What happens to oxidising agents in a redox reaction?

A

They are reduced which can be used to find what they oxidising agent.

43
Q

What happens to the dichromate ion is added to an alkanol?

A

The orange dichromate ion becomes a blue/green chromate ion?

44
Q

What happens to copper oxide when it is heated with black copper oxide?

A

The copper oxide is reduced to a red copper, the ethanol is oxidised to ethanol and H2O is produced.

45
Q

What does the oxidation of primary alcohols produce?

A

An aldehyde/alkanal.

46
Q

What does the oxidation of secondary alcohols produce?

A

Ketones\alkanones

47
Q

Can tertiary alcohols be oxidised?

A

NO

48
Q

Why do tertiary alcohols not oxidise?

A

When primary and second alcohols are oxidised, the oxidation process removes two hydrogen’s which combine with an oxygen, from the oxidising agent to form. One hydrogen comes from the -OH group an the other hydrogen comes from the the hydrogen attached to the adjacent carbon. In primary and secondary alcohols hydrogen are available in the adjacent carbon but in tertiary alcohols there are no hydrogen available.

49
Q

What is formed when acidified potassium dichromate solution is used to oxidise an aldehyde?

A

A carboxylate acid.

50
Q

What is formed when acidified potassium dichromate solution is used to oxidise an alkanal?

A

Alkanoic acid

51
Q

When an alkaline solution like Benedicts solution or Tollens reagent are used to oxidise propanol what is produced?

A

The propanoate ion.

52
Q

When an alkaline solution is used to oxidise an alcohol why is an a oats ion produced?

A

The H+ ion is neutralised by the alkaline oxidising agent.

53
Q

What can primary alcohols be oxidised to?

A

Primary alcohols can be oxidised to aldehydes which can be oxidised to carboxylic acids.

54
Q

What can secondary alcohols be oxidised to?

A

Secondary alcohols can be oxidised to ketones?

55
Q

What is an antioxidant?

A

Molecules that prevent unwanted oxidation reactions occurring by prolonging the freshness of the food.

Substances that are easily oxidised, and oxidise in place of the compounds they have been added to protect.

Can be identified as the substance being oxidised in a redox equation.

56
Q

What is an example of an antioxidant in food?

A

Vitamin C (ascorbic acid) which can be found in the list of ingredients as ascorbic acid or E300.

57
Q

What can vitamin C not prevent the oxidation of and why is this?

A

Vitamin C cannot protect fats from oxidation due to vitamin C being soluble in water.

58
Q

What is the most noticeable oxidation?

A

The reaction of oxygen with an oil or fat which produces a ‘rancid’ smell.

59
Q

Why is Vitamin C soluble in water?

A

Vitamin C is soluble in water due to the amount of OH functional groups.

60
Q

What molecule is used as an antioxidant for fats and oils?

A

The molecule BHT is an antioxidant used in fats and oils.

61
Q

Why is BHT used as an antioxidant for fats and oils?

A

BHT is insoluble in water as the vast majority is covalent with the one OH group at the top.

Z/ HIGHER Chemistry (25 decks)

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