Natures Chemistry

Question 1

What are saturated compounds

Answer 1

Only contain single carbon to carbon bonds

Question 2

What are unsaturated compounds

Answer 2

Contain atleast one carbon to carbon double bond

Question 3

What is the test for unsaturation

Answer 3

The bromine solution test
If a molecule is unsaturated the bromine becomes decolourised

Question 4

What is a homologous series

Answer 4

Family of compounds with similar chemical properties and a shared general formula

Question 5

What are isomers

Answer 5

Compounds with the same molecular formula but different structural formula

Question 6

What functional groups belongs to the alcohols (plus general formula)

Answer 6

Hydroxyl functional group = -OH
General formula = CnH2n + 1OH

Question 7

Whats the difference between primary, secondary and tertiary alcohols

Answer 7

Primary alcohols have one carbon (2 H atoms) bonded directly to C-OH whilst secondary alcohols have two carbon atoms directly bonded to the C-OH and lastly tertiary alcohols which have three carbon atoms directly bonded to the C-OH

Question 8

Are alcohols polar

Answer 8

Yes! Hydrogen bonding exists between the molecules

Question 9

What is miscibility

Answer 9

How easily a liquid solute dissolves in a liquid solvent (or how well two liquid substances mix)

Question 10

What functional group do the carboxylic acids contain ( plus general formula)

Answer 10

Carboxyl functional group = -COOH
General formula = CnH2n+1COOH

Question 11

What products do u get when a metal oxide and a carboxylic acid react

Answer 11

Salt and water

Question 12

What products do u get when a metal hydroxide and carboxylic acid react

Answer 12

Salt and water

Question 13

What products do u get when a metal carbonate and carboxylic acid

Answer 13

Salt and water and carbon dioxide

Question 14

What functional group do esters contain

Answer 14

An ester link = o-c=o

Question 15

How do esters form

Answer 15

A condensation reaction involves two molecules joining together with the elimination of a small molecule. Im this case an alcohol and carboxylic acid (water and ester form)

Question 16

What chemical is necessary to add when making esters

Answer 16

Concentrated sulfuric acid - acts as a catalyst and increases rate of reaction

Question 17

In an ester forming experiment what is added to the mouth of the test tube

Answer 17

A damp paper towel to act as a condenser

Question 18

What is hydrolysis

Answer 18

When a molecule reacts with water to break down smaller molecules

Question 19

What happens when an ester is hydrolysed

Answer 19

It reacts with water in the presence of sodium hydroxide. The ester link is broken producing the parent alcohol and carboxylic acid

Question 20

Name uses of esters

Answer 20

> Used as flavourings and fragrances
Esters have pleasant, fruity smells
Used as solvents for non-polar compounds that do not dissolve in water

Question 21

How are fats and oils formed

Answer 21

Edible fats and oils are esters. Glycerol and fatty acids are the two chemicals involved in forming fats and oils

Question 22

What is the systematic name for glycerol

Answer 22

Propane-1,2,3-triol

Question 23

What are carboxylic acids known as in fats and oils

Answer 23

Fatty acids - they cam be saturated or unsaturated straight chain carboxylic acids (usually long chains)

Question 24

How are fats and oils formed

Answer 24

The condensation of glycerol and 3 fatty acids

Question 25

Explain fully why edible oils have a lower melting point than edible fats

Answer 25

Oils are more unsaturated as they contain double bonds which cause kinks in chains of fatty acids. These kinks mean the molecules cant pack closely together and results in weaker Van Der Waals forces of attraction

Question 26

Explain fully why edible fats tend to have higher melting points than edible oils

Answer 26

Fats tend to be saturated which mean their carbon chains are are long and straight. These chains can pack closely together and therefore have stronger intermolecular forces and higher mpts

Question 27

How do you distinguish between edible fats and oils

Answer 27

Use bromine solution Unsaturated oils will quickly decolourise bromine. As the number of C-C double bonds increase so too does the volume of bromine required to decolourise it

Question 28

Why are fats and oils important for the body

Answer 28

They are a concentrated source of energy. They are essential for the transport and storage of fat-soluble vitamins in the body

Question 29

How are soaps formed

Answer 29

They are produced by the alkaline hydrolysis of edible fats and oils. This produces 3 fatty acid molecules and one glycerol molecule

Question 30

When using sodium hydroxide in alkaline hydrolysis aren the original three fatty acids formed

Answer 30

No! The fatty acids are neutralised by the alkali. Soaps are therefore fatty acid salts

Question 31

Uses of soaps

Answer 31

> used to remove non-polar substances such as oil and grease

Question 32

Describe how the structure of soaps allow them to remove non-polar substances

Answer 32

Soap ions have long non polar tails. They are hydrophobic (water-hating) Soaps have ionic negatively charged heads that are water-soluble They are hydrophilic (water-loving)

Question 33

Describe the cleaning action of soaps

Answer 33

Tails dissolvr in oil or gresse and heads remain in water Agitating the water causes ball like structures to form

Question 34

How does the greese remain suspended

Answer 34

The negatively charged balls repel each other keeping it suspended

Question 35

What happens when soap is used in hard water

Answer 35

Produces an insoluble precipitate called scum (Hard water contains high levels of dissolved metal ions)

Question 36

What solution stops scum forming in hard water

Answer 36

Soapless detergents - still have hydrophobic tails and hydrophilic heads

Question 37

What are emulsifiers used for

Answer 37

Used to prevent non polar liquids separating into layers

Question 38

How are emulsifiers similar to fats and oils

Answer 38

They are similar in the fact they have 1-2 fatty acids and a molecule of glycerol. They are made by reacting edible oils with glycerol

Question 39

How do emulsifiers differ from fats and oils

Answer 39

Whilst they form ester links with the glycerol backbone, there are still unused hydroxyl groups on the molecule

Question 40

How do emusifiers work

Answer 40

Hydroxyl groups are hydrophylic and dissolve in water, whilst fatty acid chains are hydrophobic and dissolve in oil forming a stable emulsion