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Chemistry IGCSE > Chapter 11 > Flashcards

Chapter 11 Flashcards

1
Q

What is a functional group

A

Functional group is an atom or a group of atoms that determine the chemical properties of a homologous series

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2
Q

What is structural formula?

A

It shows the unambiguous arrangement of atoms in a molecule, carbon by carbon, with the attached, hydrogen and functional groups
-> compounds with the same molecular formula but different structural formulae

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3
Q

What is a homologous series?

A

Family of similar compounds with a similar chemical properties, due to the presence of the same functional group

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4
Q

General characteristics of a homologous series

A

. Have same functional group
. Have a same general formula
. The molecular formula of a neighbouring compound in a homologous series differ by CH2 unit
. Share similar chemical properties.
. Physical properties, show trends down the series (e.g. the bigger a molecule, the higher its boiling point will be)

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5
Q

Saturated compound

A

It has molecules in which all carbon-carbon bonds are you single bonds

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6
Q

Unsaturated compound

A

Has molecules in which one or more carbon-carbon bonds are not single bonds

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7
Q

organic compounds that belong to homologous series

A

. Carboxylic acids
. Alkanes (only contain single bonded carbon and hydrogen atoms, no functional group)
. Alkenes
. Esters
. Alcohols

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8
Q

Isomers

A

Structural isomers have the same molecular formula, but there structural formulae are different. Structural isomers can be hard to spot

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9
Q

Isomers: differently shaped carbon chains

A

. Carbons could be arranged differently- as a street chain or branched for example
. They have similar chemical properties but their physical properties will be different because of change in shape of molecule

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10
Q

Isomers: functional groups in different places

A

. Arrangement of carbon atoms could be the same and isomers could have the same functional group, but functional group could be attached to a different carbon atom
. Have different physical properties

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11
Q

Coal

A

A solid fuel made from carbon

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12
Q

Natural gas

A

A mixture of gases, which forms underground, mostly made up of methane

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13
Q

petroleum

A

A mixture of lots of different hydrocarbons. Hydrocarbons found in petroleum are mostly alkanes

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14
Q

Hydrocarbons

A

Compounds that contain hydrogen and carbon only

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15
Q

Petroleum is separated into different hydrocarbon fractions (5 steps)

A
  1. Petroleum can be separated out into fractions - more useful mixtures containing groups of hydrocarbons of similar lengths
  2. Different fractions and petroleum are separated by fractional distillation petroleum is heated until most of it has to into gas - discuss enters a fractionating column
  3. In the column, there’s a temperature gradient
  4. Longer hydrocarbons have higher boiling points. They can dance and run out of the column early on, near the bottom. The shorter hydrocarbons have lower boiling points - the condense and drain out much later on, near the top of column, where its cooler
  5. Petroleum mixture separated out into a different fractions, it’s fraction contains a mixture of hydrocarbons with similar boiling points and relative molecular masses
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16
Q

Uses of the fractions: refinery gases

A

Used for heating and cooking

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17
Q

Uses of the fractions: gasoline

A

Used as fuel in cars

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18
Q

Uses of the fractions: naptha

A

Chemical feedstock

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19
Q

Uses of the fractions: kerosene

A

Used as jet fuel

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20
Q

Uses of the fractions: diesel oil

A

Used as a fuel in diesel engines

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21
Q

Uses of the fractions: Fuel oil

A

Fuel large ships and heat homes

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22
Q

Uses of the fractions: lubricating oil

A

Used to make lubricants, waxes and polishes

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23
Q

Uses of the fractions: bitumen

A

For making roads

24
Q

Properties of fractions change as you go up the column: chain lengths

A

Chain length of the hydrocarbon fractions decreases as you go further up the column.

25
Q

Properties of fractions change as you go up the column: viscosity

A

Fractions with longer chain lengths are more vicious (thick, and sticky) then those with shorter chain lengths
= viscocity of the fraction decreases as you go up the column

26
Q

Properties of fractions change as you go up the column: boiling point

A

. Hydrocarbons with longer chain lengths have higher boiling points
-> means longer chain hydrocarbons, turn back into liquids and drain out early on, closer to the bottom of the column
. Shorter chain hydrocarbons, turn into hydrocarbons at much lower temperatures, there are more volatile than longer chain hydrocarbons
= boiling point and voltality of fractions decreases up the colunm

27
Q

Alkanes

A

. Bonding is single covalent
. Alkanes are saturated hydrocarbons
. Generally unreactive, except in terms of combustion and substitution by chlorine

28
Q

Alkanes react with chlorine to make chloroalkanes

A

. In these reactions, a hydrogen atom from the alkane is substituted with chlorine. this is a substitution reaction
-> It is a type of photochemical reaction as it requires ultraviolet light to provide the activation energy
. This is how chlorine and methane react together to form chloromethane

29
Q

What is a substitution reaction?

A

A reaction where one atom, or a group of atoms in a molecule is replaced by another atom, or group of atoms

30
Q

Alkenes

A

. Double carbon-carbon covalent bond
. Unsaturated hydrocarbons - can make more bonds

31
Q

Cracking -> splitting up long chain hydrocarbons

A
  1. Long chain hydrocarbons are split into more useful short chain molecules using cracking (this is because demand for short chain hydrocarbons is much higher than longer chain, hydrocarbons. Also because they have lower boiling points, arebthinner and paler)
  2. Cracking is a form of thermal decomposition, which just means breaking molecules down into simpler molecules by heating them
  3. Cracking is an important message for producing alkenes
32
Q

Conditions for cracking - heat, plus a catalyst

A

. Powdered catalyst (Al2O3 or SiO2)
. at a high temperature (about 500°C)

33
Q

Bromine reacts with alkenes to form Bromoalkanes

A

. Add test for carbon-carbon double bonds
. When you shake an alkene with orange bromine water, the solution becomes colourless. This is because the bromine molecules, which are orange, are reacting with the alkene to make a dibromalkene, which is colourless
. Alkanes do not react with bromins water as they do not have a double bond = solution will remain orange
. Also called in addition reaction as double carbon bond is split and one bromine atom is added to each of the carbons. Only one product is formed

34
Q

Reactions of alkenes: addition of hydrogen

A

. Hydrogen can react with a double bonded carbons to open up a double bond inform the equivalent saturated alkane.
- presence of nickel catalyst

35
Q

Steam can react with alkenes to form alcohols

A
  1. When alkenes reacts with steam, water is added across the double bond and an alcohol is formed
    . Using a catalyst
36
Q

Alcohols are oxidise when they are burnt

A
  1. When alcohols are burnt in enough oxygen, they undergo complete combustion
  2. The products of this reaction are water and carbon dioxide
  3. The alcohol is oxidised in this reaction
37
Q

Alcohols are used as solvents and fuels: solvents

A

Alcohols such as ethanol are used as solvents in industry
-> This is because they can dissolve most things water can dissolve also dissolve substances that water cant dissolve

38
Q

Alcohols are used as solvents and fuels: fuels

A

. For example, ethanol is used as a fuel in spirit burners - it burns fairly clearly, and is not smelly

39
Q

Ethanol produced from ethene and steam (5)

A
  1. Ethene is produced from petroleum (by cracking)
  2. Ethene will reacts with steam to make ethanol.
  3. This is an addition reaction because water is added to the molecule
  4. The reaction needs a high temperature (300°C) and a high-pressure (600 kPa or 60 atmospheres)
  5. Phosphoric acid used as a catalyst
40
Q

Disadvantages for production of ethanol from ethene and steam

A

. Petroleum is a nonrenewable resource -> very expensive
. Requires a lot of energy

41
Q

Advantages for production of ethanol from ethene and steam

A

. At the moment, it is a cheap process, because ethene’s fairly cheap, and not much of it is wasted

42
Q

Ethanol produced by fermentation (5)

A
  1. Raw material for fermentation is a solution of simple sugars which are converted into ethanol using yeast
  2. Yeast cells contain enzymes
  3. Fermentation mixture needs to be about 25–35°C -> add lower temperatures reaction slow down or higher causes denaturing of enzymes
  4. Keep mixture in anaerobic conditions (no oxygen)
  5. After fermentation, ethanol is distilled to increase its concentration
43
Q

Advantages for ethanol produced by fermentation

A

. Raw materials, used or renewable sources - sugar and east are very easily grown

44
Q

Disadvantages for production of ethanol by fermentation

A

. Ethanol is it very concentrated, so it needs to be distilled to increase its strength. It also needs to be purified
. Slower process (as it is a batch process)

45
Q

carboxylic acids

A

-COOH functional group and names end in ‘-oic acid’
. Ethanoic acids is a carboxylic acid with two carbons

46
Q

Making carboxylic acid by oxidising alcohol

A

. Methanoic acid, propanoic acid and butanoic acid can be formed by:
-> oxidising the alcohol, which contains the same total number of carbons. You need an oxidising agent for this such as acidified aquaeous potassium manganate.

47
Q

Carboxylic acids made by fermenting alcohols

A
  1. Ethanol can be oxidised by fermentation into a carboxylic acid
  2. In this process, Ethan reacts with oxygen in the air to produce ethanol week acid (vinegar) (and water). The reaction is carried out by bacteria the solution.
  3. Process is slow -> This is the reason why beer and wine can taste sour of their left exposed to the air for a couple of days
48
Q

Esters made from carboxylic acids in alcohol

A
  1. Esters have functional group ‘-COO-‘
  2. Esters are formed from an alcohol and a carboxylic acid
  3. An acid catalyst is usually used (e.g. concentrated sulphuric acid)
49
Q

Polymers

A

Large molecules made by joining up lots of small repeating units called monomers

50
Q

Addition polymerisation

A

. When alkene monomers open up the carbon-carbon double bond, and join together to form polymer chains

51
Q

Condensation polymerisation (4)

A
  1. Involves monomers which contain different functional groups
  2. The monomers react together and bonds form between them, making polymer chains
  3. For each new bond that forms, a small molecule is lost. This is why it’s called condensation polymerisation
  4. Many common condensation polymers are made from two different monomers, with each one, having two of the same functional groups
52
Q

Addition and condensation, polymerisation or different: addition polymerisation -> number of products; number of types of monomers; functional groups involved in polymerisation

A

. Number of products: only one product formed.
. Number of types of monomers: only one mono more type containing a C=C bond
. Functional groups involved in polymerisation: carbon-carbon double bond in monomer

53
Q

Addition and condensation, polymerisation or different: condensation polymerisation -> number of products; number of types of monomers; functional groups involved in polymerisation

A

. Number of products: two types of product - the polymer and a small molecule
. Number of types of monomers: to monomer types, each containing two of the same functional groups OR one monomer type with two different functional groups
. Functional groups involved in polymerisation: two reactive groups on each monomer

54
Q

Man-made polymers have many uses

A
  1. Plastics are a group of man-made polymers, traditionally produced from petroleum
  2. Other useful man-made polymers include nylon (a polyamide) and PET (a polyester)
  3. PET is particularly useful as it can be broken down into monomers and recycled into new polymers
55
Q

Disposal of plastics: pollution, problems

A

. Plastics takes long time to biodegrade
. Most addition, polymers are difficult to biodegrade because they’re inert - don’t react easily
-> plastic buildup in the oceans (threat to aquatic life)
-> disposal in landfill sites when polymers are too difficult to expensive to separate and recycle
-> burning plastics produces a lot of energy and can be used to generate electricity. However, it also releases toxic gases contributing to global warming

56
Q

Proteins

A

Natural polyamides
. Formed from amino acid monomers via condensation polymerisation to create chains
. Proteins can contain different amino acids in the polymer chains. The order of amino acids is what gives proteins their different properties and structures.

Chemistry IGCSE (11 decks)

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