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Chemistry GCSE > SC9 - Organic Chemistry > Flashcards

SC9 - Organic Chemistry Flashcards

1
Q

What are hydrocarbons?

A

Molecular compounds which contain only carbon and hydrogen atoms.

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2
Q

What are alkanes?

A

Alkanes are a group of hydrocarbons which are based on a chain of carbon atoms. They are saturated (no double covalent bonds). They are in the same homologous series.

E.g. Ethane

H H
 I   I

H-C-C-H
I I
H H

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3
Q

What is a homologous series?

A

A group of chemicals which have the same general formula, similar chemical properties and show a trend in physical properties.

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4
Q

What is the general formula for alkanes?

A

CnH2n+2

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5
Q

What are the prefixes for the first 4 hydrocarbons?

A

Meth- (1 carbon)
Eth- (2 carbons)
Prop- (3 carbons)
But- (4 carbons)

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6
Q

What are alkenes?

A

Unsaturated hydrocarbons (contain a double covalent bond between carbon atoms).

E.g. Ethene

H H
I I
C=C
I I
H H

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7
Q

What is the general formula for alkenes?

A

CnH2n

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8
Q

What is a functional group?

A

The atom or group of atoms which are mainly responsible for a molecule’s chemical properties.

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9
Q

What is the functional group for alkenes?

A

C=C

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10
Q

What is the functional group for alkanes?

A

C-C

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11
Q

What is an isomer?

A

An isomer is a molecule with the same molecular formula but different arrangements of atoms (e.g. but-1-ene has the C=C bond first, but-2-ene has the C=C bond second)

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12
Q

What is formed during the complete combustion of hydrocarbons?

A

Carbon dioxide and water only

E,g. Methane + oxygen —> carbon dioxide + water

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13
Q

What is formed during the incomplete combustion of a hydrocarbon?

A

Particulate carbon (soot) may form as well as or instead of water and carbon dioxide.

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14
Q

What is the test for alkenes?

A

Bromine water is an orange-brown colour. When it is mixed with alkenes a chemical reaction occurs, leading to colourless products. Alkanes do nit cause this decolourisation.

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15
Q

What happens during the reaction of ethene and bromine water?

A

This is an addition reaction (the carbon double bond opens up and forms a structure like an alkane with the bromine in it)

ethene + bromine —> 1,2-dibromoethane

H H H H
I I I I
C=C + Br2 —> H-C-C-H
I I I I
H H Br Br

The 1,2 means that the two bromine atoms are attached to different carbon atoms (the first bromine is attached to the first carbon, the second bromine is attached to the second carbon.

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16
Q

What is an addition reaction?

A

A reaction in which the reactants combine to form one larger product molecule and no other products.

17
Q

How is ethanol produced?

A

The ethanol in alcoholic drinks is made form sugars (starch in plants is broken down into sugars e.g. Beer uses barley, wine uses grapes). Plant material containing sugars is mixed with yeast and enzymes in the yeast turn the sugars into ethanol and carbon dioxide (fermentation)

Glucose —> ethanol + carbon dioxide

18
Q

How can alcohol be concentrated to make spirits?

A

Concentrated solutions of ethanol are made using fractional distillation. The boiling point of ethanol is 78 degrees C, lower than water (100 degrees C). The solution is heated and the evaporated liquids rise up the fractionating column. As ethanol has a lower boiling point, it remains as a gas for longer and separates from the water.

19
Q

What are alcohols?

A

Alcohols are a homologous series which are similar in structure to alkanes but have an oxygen atom as well.

E.g. Ethanol

H H
 I  I

H-C-C-O-H
I I
H H

20
Q

What are some chemical properties of alcohols?

A
  • they produce carbon dioxide and water on complete combustion
  • they can be oxidised to form carboxylic acids
  • they react with reactive metals, such as sodium, forming hydrogen gas as one of the products
21
Q

What is the general formula for alcohols?

A

CnH2n+1OH

22
Q

What is the functional group for alcohols?

A

-OH

23
Q

What are some uses of alcohols?

A

Alcoholic drinks, solvents for cosmetics, medical drugs and varnishes. Methanol and ethanol are widely used as fuels and can be made from renewable sources.

24
Q

Core practical - the combustion of alcohols

A
  • measure the mass of the alcohol burner and cap. Record the mass and name of the alcohol
  • place the alcohol burner in the centre of a heat-resistant mat
  • use a measuring cylinder to add 100cm3 of cold water to a conical flask
  • measure and record the initial temperature of the water and clamp the flask above the alcohol burner
  • light the wick of the burner and allow the water to heat up by 40 degrees C
  • replace the cap on the burner and measure and record the final temperature of the water
  • measure the mass of the alcohol burner and cap again and record the mass
  • calculate the mass of alcohol burned to produce a 1 degree rise in temperature
  • repeat the method using fresh, cold water and a different alcohol
25
Q

What are carboxylic acids?

A

They are a homologous series made by oxidising alcohols.

E.g. Ethanoic acid

H O
 I  II

H-C-C-O-H
I
H

26
Q

What is the functional group for carboxylic acids?

A

-COOH

27
Q

What is the general formula for carboxylic acids?

A

CnH2n+1COOH

28
Q

What are some chemical properties of carboxylic acids?

A
  • form solutions with a pH less than 7
  • react with metals to form a salt and hydrogen
  • ract with bases to form a salt and water
  • react with carbonates to form a salt, water and carbon dioxide
29
Q

Are carboxylic acids strong or weak?

A

They are weak acids (only some dissociate into H+ and COO-, most remain as COOH)

30
Q

What are polymers?

A

A polymer is a large molecule made form lots of small molecules (monomers) joined together.

31
Q

How does addition polymerisation work?

A

The double covalent bond in an alkene breaks and another molecule adds on (e.g. poly(ethene) is formed by ethene molecules joining together in this way).

32
Q

What are some examples of naturally occurring polymers?

A

DNA, starch, proteins

33
Q

What are some uses for some polymers?

A

Poly(ethene) (polythene) - plastic bags, plastic bottles, cling film
Poly(propene) (polypropylene) - buckets and bowls, crates, ropes, carpets
Poly(chloroethene) (PVC) - window frames, gutters, insulation for electrical wires
Poly(tetraflouroethene) (PTFE / Teflon) - non-stick coatings for frying pans, burette taps, stain-proofing clothing and carpets

34
Q

What is condensation polymerisation?

A

A reaction in which monomers join together and eliminate a small molecule, such as water.

35
Q

What is an ester?

A

An ester is an organic compound which forms when carboxylic acids react with alcohols.

36
Q

What is the functional group for esters?

A

-COO-

O
II
-C-O-

Chemistry GCSE (10 decks)

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