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Z. Higher Chemistry > Unit 2 > Flashcards

Unit 2 Flashcards

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1
Q

Describe the term saturated compounds

A

Saturated compounds only contain C-C single bonds.

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2
Q

Describe the term unsaturated compounds

A

Unsaturated compounds contain at least one C=C double bond.

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3
Q

Hydrogenation

A

Hydrogenation - reaction between an alkene and H2 formingan alkane.

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4
Q

Hydration

A

Hydration - reaction between an alkene and water forming an alcohol.

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5
Q

Addition reaction - alkenes

A

Alkenes reacting with halogens forming dihaloalkanes.

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6
Q

Test to Distinguish between saturated and unsaturated compounds

A

Unsaturated compounds decolourise bromine solution

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7
Q

Isomers

A

Isomers are compounds with the same molecular formula but different structural formulas.

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8
Q

How does Compund size affect its properties

A

The bigger the compound, the less soluble they are, the higher the boiling point and the volatility decreases.

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9
Q

Why does BP increase as compound size increases?

A

Boiling point increases as the compounds increase in size due to stronger LDFs (and even higher when Hydrogen bonding or Pd-Pd interactions are present).

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10
Q

What do polar and ionic compounds tend to be soluble in

A

Polar and ionic compounds tend to be soluble in polar solvents.

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11
Q

What affects volatility

A

Volatility (measure of the ease of evaporation) is affected by intermolecular forces present.

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12
Q

Alcohol functional group

A

Hydroxyl (-OH) functional group.

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13
Q

Describe primary alcohols

A

-OH group attached to a C atom which has 2 other H’s (Or C atom the OH is connected to is only connected to 1 other C atom). This only occurs when the -OH group is at the end of the molecule.

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14
Q

Describe secondary alcohols

A

-OH is attached to a carbon with only one hydrogen atom attached (or C atom OH is attached to has 2 other C atoms).

This can happen somewhere in the middle of a carbon chain.

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15
Q

Describe tertiary alcohols

A

-OH group is attached to a C atom with no other hydrogen atoms attached ( or C atom attached to 3 other C atoms).

This will mean that the hydroxyl group is joined to the same C atom as a branch.

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16
Q

Describe diol alcohols

A

Alcohols with 2 hydroxyl groups

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17
Q

Describe triol alcohols

A

Alcohols with 3 hydroxyl groups

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18
Q

Explain the effect the hydroxyl group has on an alcohol’s physical properties

A

Alcohols with more hydroxyl groups will have higher melting and boiling points (due to greater degree of hydrogen bonding).

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19
Q

State carboxyl functional group

A

Carboxyl (-COOH) functional group

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20
Q

State the reactions that carboxylic acids can have with bases

A

When reacted with bases, carboxylic acid takes part in a neutralisation reaction, producing a salt and water.

metal oxide + carboxylic acid → salt + water

metal hydroxide + carboxylic acid → salt + water

metal carbonate + carboxylic acid → salt + water + carbon dioxide

(When long chained fatty acids are used, soap is produced).

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21
Q

Ester link

A 
.   O
.   ll
   C.       R
 /    \    /
R        O
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22
Q

What produces esters

A

Esters are formed by a condensation reaction between an alcohol and a carboxylic acid with the elimination of water.

The name of an ester comes from its ‘parent’ alcohol and carboxylic acid.

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23
Q

Ester uses

A

Esters are used as flavourings, fragrances and solvents for other non-polar compounds.

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24
Q

Reaction that forms and breaks esters apart

A

Condensation forms esters.

Hydrolysis breaks esters

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25
Q

Describe a condensation reaction

A

Esters are formed by a condensation reaction between an alcohol and a carboxylic acid with the elimination of water.

Making an ester - esterification reaction

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26
Q

Describe a hydrolysis reaction

A

Hydrolysis is the breaking of large molecules into smaller molecules by the addition of water.

The ‘parent’ alcohol and carboxylic acid are formed.

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27
Q

Describe how edible fats and oils are formed

A

Edible fats and oils are esters formed from the condensations of glycerol (propan-1,2,3-triol).

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28
Q

Explain why there is a difference in melting points of fats and oils

A

Oils have a lower melting point than fats.

Oils have more unsaturated (more double bonds). These double bonds prevent the molecules from packing as closely together, so the intermolecular forces are weaker - leading to a lower melting point.

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29
Q

Describe the test for saturation

A

Unsaturated compounds decolourise bromine solution

30
Q

Why do we need fats and oils

A

Fats and oils are a really concentrated source of energy for us. They are also essential for the transport and storage of fat-soluble vitamins for our bodies.

31
Q

How are soaps formed

A

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

This hydrolysis produces 3 fatty acid molecules and glycerol.

The fatty acid molecules are then neutralised by an alkali, forming ionic (water soluble) salts, which we call soaps.

Emulsifiers are also made by alkaline hydrolysis is edible oils.

32
Q

Use of soaps

A

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

33
Q

How do soaps work

A

Soaps have a polar, hydrophilic, ionic head and a non-polar, hydrophobic tail. When in contact with oil and water, the hydrophobic tail will enter the oil, leaving the hydrophilic head in the water.

Agitation of the oil/grease then forms small balls called micelles. They are held in this suspension (stay in micelles) as the negative heads repel each other preventing them combining together.

Micelles are formed and the negative heads repel each other.

34
Q

Describe the term hard water

A

Hard water is water containing high levels of dissolved metal ions. Scum (an insoluble precipitate) is commonly found in areas which have hard water.

35
Q

Describe the term soapless detergents and explain when they might be used

A

Soapless detergents have non-polar hydrophobic tails and ionic hydrophilic heads to remove oil and grease like normal soaps.

They do not form scum with hard water so are best used in areas which suffer from this.

36
Q

Emulsifier use

A

Emulsifiers prevent non-polar and polar liquids separating into layers.

37
Q

How do emulsifiers work

A

Emulsifiers have similar structures to fats and oils but have one or two fatty acid groups that can be added to glycerol.

While this forms an ester link with the glycerol there is still unused hydroxyl groups so there is a non-polar hydrophobic part which can dissolve in oil and a polar, hydrophilic (OH) group which can dissolve in water.

38
Q

Where are emulsifiers used

A

They are used in foods to prevent oil and water separating.

39
Q

Role of proteins

A

Proteins are major structural materials of animal tissues and are essential for the maintenance and regulation of life processes.

40
Q

What makes proteins

A

Proteins are made from amino acids (building blocks of proteins).

41
Q

Describe the groups contained in an amino acid

A

All amino acids contain an amino group, -NH2 and a carboxyl group, -COOH.

42
Q

Describe how proteins are formed

A

Proteins are formed when one amino group and the carboxyl group of another amino acid join together (make a peptide link) with the elimination of water.

43
Q

Peptide link

A

-CONH-

O.     H
||     | — C — N —
44
Q

Describe the term essential amino acids

A

Essential amino acids are ones required by the body for protein synthesis but must be acquired through the diet.

45
Q

What happens to proteins during digestion

A

Proteins are broken down during digestion via enzyme hydrolysis.

46
Q

Explain how proteins get their shape, and how temperature affects this

A

Proteins can form complex shapes. They are kept in these shapes by intermolecular bonds.

When they are heated, these bonds are broken which causes the protein to change shape (denatured). This change in shape causes the texture of food to change when heated.

47
Q

Explain oxidation and reduction using oxygen to hydrogen ratio

A

Oxidation – increase in the oxygen to hydrogen ratio.

Reduction – decrease in the oxygen to hydrogen ratio.

48
Q

Oxidation of alcohols

A

Primary alcohols → aldehydes → carboxylic acids

Secondary alcohols → ketones

49
Q

oxidising agents and their colour changes

A

Hot copper (II) oxide – black to brown solid

Acidified dichromate (VI) solution – orange to green

Fehling’s solution – blue to brick red

Tollens’ reagent – forms a silver mirror

50
Q

State what oxidising agents can be used to identify

A

Oxidising agents can be used to identify aldehydes (not ketones).

51
Q

Explain why tertiary alcohols cannot be oxidised

A

Tertiary alcohols cannot be oxidised due to the position of the hydroxyl group – due to there being a branch, a =O cannot be formed.

52
Q

Functional groups found in aldehydes and ketones

A

Carbonyl C=O

Draw ketone and aldehyde funvtional groups on whiteboard

53
Q

Oxidation and reduction reactions of aldehydes and ketones

A

Oxidation
Aldehydes → Carboxylic acids
Ketones → no oxidation

Reduction
Aldehydes → primary alcohol
Ketones → secondary alcohol

54
Q

Uses of aldehydes

A

Aldehydes often have distinct flavours and aromas so can be used in food products or essential oils.

55
Q

What happens when food reacts with air

A

Food reacts with oxygen from the air. This then reacts with edible oils giving them a rancid flavour (the food goes ‘off’).

56
Q

Describe and explain the term antioxidant

A

Antioxidants are molecules that prevent unwanted oxidation reactions to occur by being oxidised in their place (they are reducing agents)

Example - vitamin C

57
Q

Describe the term essential oil and state its properties and uses

A

Essential oils are concentrated extracts of volatile, non-water soluble aroma compounds which come from plants.

58
Q

Describe a terpene

A

Terpenes are unsaturated hydrocarbons made from isoprene (2-methylbuta-1,3-diene) units bonding together.

They can be recognised by the compound only containing isoprene units.

59
Q

What happens when terpenes are oxidised

A

When oxidised, terpenes release the distinctive aroma found in spices (such as ginger and cinnamon).

60
Q

Describe the reaction ultraviolet light can have on the body

A

Ultraviolet (UV) light is high-energy which can break bonds within molecules (causing sunburn, ageing and cancer).

61
Q

Free radical meaning

A

A free radical is an atom (or molecule) that is highly reactive as it has an unpaired electron, eg H·

62
Q

Chain reaction steps

A

1) Initiation
2) Propagation
3) Termination

Initiation:
All the free radicals will be on the products side.

Propagation:
There will be a free radical on both the product and reactant side.

Termination:
Both free radicals will be on the reactant side.

63
Q

Explain the term free radical scavengers and give examples of when they would be used

A

Free radical scavengers are molecules that react with free radicals to form stable molecules.

They are added to skin care products, cosmetics, plastics and foods to prevent any chain reactions from taking place for example, preventing bonds breaking in your skin.

64
Q

Fibrous and globular proteins solubility in water

A

Fibrous proteins - not soluble in water

Globular proteins- generally soluble in water

65
Q

How are emulsifiers made

A

Reacting edible oils with glycerol

66
Q

Isoprene unit

A

2 - methylbuta-1,3-diene

Is a hydrocarbon (contains H and C atoms only)

(Draw of board) fragrances on lets achieve

To state no of isporene units: count carbon atoms and divide by 5

67
Q

Homologous series

A

A family of hydrocarbons with the same general formula and similar chemical properties.

The physical properties change as the carbon chain increases.

68
Q

Essential oils uses

A

Often used in flavourings, fragrances, cosmetic products and cleaning products.

69
Q

Aldehyde functional group

A 
Carbonyl 
      O 
     ||
     C
   /   \
R       H

(Has a hydrogen attached - at end of molecule)

70
Q

Ketone functional group

A 
Carbonyl 
     O
    ||
    C
  /    \
R       R

(Carbonyl group attached to other carbons - never at end of the molecule)

Z. Higher Chemistry (4 decks)

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