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N...5 Ch,,emist. ry > Unit 2 - Hydrocarbons > Flashcards

Unit 2 - Hydrocarbons Flashcards

1
Q

What is a fuel?

A

Fuels are substances which are burnt to produce energy.

The energy is stored as chemical energy and is released as heat and light energy when burnt.

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2
Q

What is crude oil?

A

Crude oil is a very complex mixture of chemical compounds called hydrocarbons.

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3
Q

What elements are in hydrocarbons?

A

Hydrocarbons contain carbon and hydrogen only.

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4
Q

What is combustion?

A

Combustion is the burning of a substance in oxygen.

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5
Q

What type of reaction is combustion?

A

Exothermic reaction because heat energy is released.

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6
Q

What components need to be present for a fire to continue?

A

Fuel
Oxygen
Heat

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7
Q

How is crude oil (hydrocarbons) separated?

How are the fractions separated?

A

The crude oil needs to be separated using a process called fractional distillation.

The fractions are separated by the difference in their temperature ranges.

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8
Q

What is always produced during the combustion of any hydrocarbon?

A

Carbon dioxide, water

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9
Q

Properties of fractions - hydrocarbons chains

A

Hydrocarbons are made up of chains of carbon atoms of different lengths.

(Some with only one or two carbon atoms; others with seventy carbon atoms.) The length of the hydrocarbon chain affects the physical and chemical properties of the fractions.?

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10
Q

What is viscosity?

A

Viscosity is the thickness of a liquid.

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11
Q

What happens is a substance is more Volatile or less Volatile?

A

The more volatile a substance is, the more easily it evaporates.

The less Volatile a substance is, the less easily it evaporates.

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12
Q

What is incomplete combustion?

A

If there is INSUFFICIENT oxygen to completely burn a fuel, incomplete combustion occurs.

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13
Q

What is a catalytic convertor?

A

A catalytic convertor is an exhaust emission control device that reduces toxic gases and pollutants in exhaust gas from an internal combustion engine into a less toxic pollutant.

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14
Q

What type of energy is released when a fuel burns?

A

When a fuel burns it releases energy, this is known as an exothermic reaction. (Releases heat energy)

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15
Q

Formula for measuring energy by heating up water?

A

Specific Heat Capacity of water

Eh = cm🔺️T

Eh=
c =
m =
🔺️T =

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16
Q

What are alkanes?

A

Alkanes are a group of hydrocarbons that are made up of chains of carbon atoms joined together by single covalent bonds.

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17
Q

What are alkanes described as?

A

Saturated because each carbon atom has the max number of hydrogen atoms that can bond to it (the carbon).

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18
Q

General formula of alkanes

A

C(n)H(2n+2)

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19
Q

Properties of alkanes

A

Saturated hydrocarbons - Alkanes have all there bonds used, so they are unreactive.

Insoluble in water

Used as fuels

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20
Q

How are alkenes produced?

A

AlkENES are produced from cracking of long chain alkanes.

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21
Q

What is cracking?

A

Cracking is breaking up long chain alkanes into more useful short chain products.

A mixture of alkanes and alkenes are produced.

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22
Q

General formula of alkenes

A

CnH2n

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23
Q

Properties of alkenes

A

Alkenes are unsaturated hydrocarbons.

They are chemically reactive (used to make polymers and alcohols via addition reactions)

Insoluble in water

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24
Q

What are cycloalkanes?

A

Cycloalkanes are SATURATED hydrocarbons.

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25
Q

What are cycloalkenes?

A

Cycloalkenes are UNSATURATED hydrocarbons.

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26
Q

Definition of a 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.

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27
Q

Definition of an isomer

A

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

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28
Q

What are functional groups?

A

Identifying features are called functional groups.

29
Q

AlkENES and cycloalkANES

A

Alkenes and cycloalkanes are isomers of each other.

30
Q

Cycloalkanes general formula

A

CnH2n

This is the same general formula as alkENES.

31
Q

Cycloalkenes general formula

A

CnH2n-2

32
Q

What are addidion reactions?

A

Addition reactions - adding a small molecule across the carbon-to-carbon double bond.

An addition reaction is when 2 (or more) molecules join together to form a larger one. The reaction involves breaking double C=C double or triple bonds.

Careful for diatomic molecules: e.g. hydrogen = H2

33
Q

Addition reaction - hydrogenation

A

Adding H2 to an alkene making and alkane.

34
Q

What do unsaturated compounds contain?

A

Unsaturated compounds contain at least one carbon-to-carbon double bonds.

35
Q

How can unsaturated compounds and saturated compounds be distinguished?

A

Reacting them with bromine water.

36
Q

Test for unsaturated definition

A

Unsaturated compounds turn bromine solution/water colourless.

37
Q

Physical properties of hydrocarbons

A

Melting and boiling points increase as the carbon chain increases. This is due to larger intermolecular forces. (NO COVALENT BONDS ARE BROKEN when covalent molecules melt/boil.)

Insoluble in water

DO NOT conduct electricity

38
Q

Uses of hydrocarbons

A

Alkanes - fuels

Alkenes - make alcohols and polymers from addition reactions.

Cycloalkanes - solvents, fuels

39
Q

Carbohydrates

A

(Carbon, hydrogen, oxygen)

  • sugars
  • alcohols
  • carboxylic acids
40
Q

Functional group of alcohols

A

Hydroxyl group (OH)

41
Q

General formula of alcohols

A

CnH2n+1OH

42
Q

Test for starch

A

The test for starch is the iodine solution turned from red-brown to blue-black.

43
Q

Test for glucose

A

The test for glucose is the benedicts’ solution turned from bright blue to brick orange.

44
Q

Properties of alcohols

A

Clear liquids

Melting and boiling points increase as chain length increases because larger intermolecular forces.

Viscosity increases

Flammability decreases

1st 3 - soluble in water - after that solubility decreases with chain length.

45
Q

Uses of alcohols

A

Fuels

Kills bacteria/ viruses - hand sanitiser, mouthwash

Solvents - substances that may not be soluble in water may be soluble in alcohols.

46
Q

Energy from fuels test

A

Draw

Explain stages?

47
Q

Combustion of alcohol and energy calculations formula

A

Eh = cm🔺️T

Eh = heat energy (kJ)
c = specific heat capacity of water (4.18kJkg-¹°C-¹)
m = mass of water (kg) 
🔺️T = change in temperature (°C)
48
Q

Burning fuels experiment inaccuracies and solutions

A

Heat lost to surroundings

  • can be reduced by insulation/ draught excluder
  • can reduce distance from burner to metal cup

Incomplete combustion

Fuel evaporates

49
Q

Burning fuels experiment - Bomb Calorimeter

A

More accurate because:

  • no heat lost due to surroundings (all heat goes to water)
  • no incomplete combustion (as there is a constant supply of oxygen)
  • no evaporation of fuel (enclosed “bomb”)
50
Q

What are carboxylic acids?

A

Carboxylic acids are a homologous series with a carboxyl functional group.

51
Q

Carboxylic acids general formula

A

CnH(2n+1)COOH

52
Q

Properties of Carboxylic acids

A
  • Liquids at room temperature
  • melting and boiling points increase with chain/molecule size because the INTERMOLECULAR FORCES INCREASE.
  • strong (pungent) smelling
  • solubility- 1st 4 acids are soluble in water (solubility decreases as molecule size increases)
53
Q

Uses of Carboxylic acid

A
  • flavouring
  • food preservation
  • cleaning products
  • medicines
54
Q

Reactions of Carboxylic acids

A

React with metals - gives off H2

Neutralise bases - hydroxides, carbonates, oxides

Conduct electricity

55
Q

What are organic compounds?

A

Organic compounds are molecules that contain carbon.

56
Q

First 8 prefix names

A 
1 - meth
2 - eth
3 - prop
4 - but
5 - pent 
6 - hex
7 - hept 
8 - oct
57
Q

What is an exothermic reaction

A

An exothermic reaction is a reaction which releases heat energy.

58
Q

What is an endothermic reaction?

A

An endothermic reaction is a reaction which takes in heat energy.

59
Q

What are identifying features?

A

Functional groups

60
Q

What do all alkenes have?

A

A carbon to carbon double bond. (Or more)

61
Q

Describe saturated compounds

A

Saturated compounds only contain C-C single bonds.

62
Q

Describe unsaturated compounds

A

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

63
Q

Addition reaction - hydration

A

Adding H2O to an alkene making an alcohol.

Reaction between an alkene and water forming an alcohol.

64
Q

Alcohols up to C8

A 
Methanol
Ethanol
Propan-1-ol
Butan-1-ol
Pentan-1-ol
Hexan-1-ol
Heptan-1-ol
Octan-1-ol
65
Q

Carboxylic functional group

A

Carboxyl (COOH)

66
Q

Carboxylic acids up to C8

A 
Mathanoic acid
Ethanoic acid
Propanoic acid
Butanoic acid
Pentanoic acid
Hexanoic acid
Heptanoic acid 
Octanoic acid
67
Q

Definition of a combustion reaction

A

Combustion reaction is when a substance reacts with oxygen and releases energy.

When hydrocarbons and alcohols react with oxygen, water and carbon dioxide is released.

68
Q

What do saturated compounds contain

A

Only contain C-C single bonds.

N...5 Ch,,emist. ry (7 decks)

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