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GCSE chemistry > C6.2 > Flashcards

C6.2 Flashcards

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1
Q

Hydrocarbons

A

Compounds that only contain hydrogen and carbon atoms

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2
Q

What are alkanes

A

Homologous hydrocarbons

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3
Q

Why do alkanes from a homologous series

A

They have common features :
-same general formula
-carbon atoms are joined together by single covalent bonds
All alkanes are SATURATED

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4
Q

Are alkanes saturated or non saturated

A

Saturated

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5
Q

General formula for alkanes

A

CnH2n+2
Each successive member differs by a CH2 group

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6
Q

How do alkanes react

A

Through combustion
If there is a plentiful supply of oxygen or air , complete combustion happens

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7
Q

Are the atoms oxidised or reduced during combustion

A

Carbon atoms are oxidised , forming carbon dioxide
Hydrogen atoms are oxidised , forming water

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8
Q

What happens if there is a poor supple of oxygen or air during combustion

A

Incomplete combustion happens instead
Water is formed , but carbon is only oxidised to carbon monoxide , CO
Some carbon atoms may not be oxidised if there is a further lack in oxygen or air , forming C

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9
Q

Why is CO bad

A

It is a toxic gas and can cause suffocation

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10
Q

Crude oil

A

A fossil fuel formed from the remains of marine organisms that died millions of years ago , turning into crude oil due to chemical reactions

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11
Q

Finite resources

A

No longer being made or are being made extremely slowly , and is being used up faster than being formed

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12
Q

Features of a homologous series

A

Saturated - all atoms joined together by simple covalent bonds
Same general formula
All differ by CH2

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13
Q

What type of compounds are alkanes

A

Colourless , but have gradual physical property changes as the number of carbon atoms in the chain increase
Generally unreactive

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14
Q

CH4

A

Methane

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15
Q

C2H6

A

Ethane

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16
Q

C3H8

A

Propane

17
Q

C4H10

A

Butane

18
Q

Name the first four alkanes

A

Methane , ethane , propane , butane

19
Q

What are alkenes

A

Hydrocarbons that form a homologous series

20
Q

What is the main difference between alkanes and alkenes

A

Alkene molecules contain a C=C double bond
This means that alkenes are unsaturated

21
Q

General formula for alkenes

A

CnH2n

22
Q

Functional group

A

An atom , or group of atoms , or type of bond in a molecule that uses responsible for the characteristic reactions of the substance

23
Q

In alkenes , which bond allows the substance to undergo additional reactions

A

The C=C double bond

24
Q

Addition reaction

A

An atom or group of atoms combines with a molecule to form a larger molecule , with no other
products formed

25
Q

Basic test for unsaturation

A

Bromine reacts with alkenes but not alkanes . Bromine water is orange brown , but will turn colourless if an alkene is mixed with it . It remains orange brown if an alkane is added to it

26
Q

Alkenes can also undergo addition reactions with hydrogen in the presence of

A

A nickel catalyst

27
Q

The more carbon atoms there are in the alkane molecules

A

-the larger the molecules
-the stronger the intermolecular forces
-the higher the boiling point

28
Q

How is crude oil made useful

A

It is made up of a mixture of hydrocarbons , mostly alkanes
They are separated using fractional distillation . This works well because each alkane has a different boiling point

29
Q

Describe the process of fractional distillation - crude oil

A

-Crude oil is heated and it’s vapours are piped into the bottom of a fractionating column , which has a a temperature gradient ( hot at the bottom , cold at the top )
-Vapours cool as they rise through the column
-each fraction contains many substances with similar boiling points

30
Q

Fraction

A

Separated parts of the crude oil

31
Q

Which alkane has the highest boiling point

A

Bitumen , during fractional distillation it leaves at the bottom of the column and is in the solid state at room temperature

32
Q

Which substances have the lowest boiling points during fractional distillation

A

Refinery gases - methane , ethane , propane , and butane have the lowest boiling points
They reach the top and leave the column without cooling enough to condense

33
Q

The other substances

A

Are in liquid state at room temperature, they fall into trays and leave from the middle of the column

GCSE chemistry (3 decks)

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