An allotrope is one of two or more different structural forms of the same element. Diamond , graphite , graphene , and fullerenes are all allotropes of carbon.

Why does diamond not conduct electricity?

In diamond , each carbon atom forms four covalent bonds to other carbon atoms, using all its outer electrons. There are no delocalised (free) electrons to carry a charge, so diamond cannot conduct electricity.

True or False? Graphite can conduct electricity because it has delocalised electrons between its layers.

True. In graphite , each carbon atom forms only three covalent bonds, leaving one free ( delocalised ) electron per carbon atom. These electrons can move between the layers and carry charge, allowing graphite to conduct electricity .

Why is graphite soft and slippery, making it useful as a lubricant?

Graphite is arranged in layers. Within layers, carbon atoms are held by strong covalent bonds , but between layers there are only weak intermolecular forces . These allow the layers to slide over each other easily, giving graphite its soft, slippery properties.

Graphene is a single layer of graphite — a one-atom-thick sheet of carbon atoms arranged in a hexagonal lattice. It is extremely strong, flexible, transparent, and conducts electricity due to delocalised electrons.

Fullerenes are molecules of carbon atoms with .......... shapes. The first fullerene discovered was .......... , which contains .......... carbon atoms and has a .......... shape.

Fullerenes are molecules of carbon atoms with hollow shapes. The first fullerene discovered was Buckminsterfullerene , which contains 60 carbon atoms and has a spherical shape.

State two uses of carbon nanotubes.

Carbon nanotubes are used in: Nanotechnology and electronics — due to high electrical conductivity Composite materials — due to their high tensile strength and low density

True or False? Fullerenes can be used in targeted drug delivery because they can trap other molecules inside their hollow structures.

True. Fullerenes have hollow, cage-like structures that can trap other molecules inside them. This makes them useful for delivering drug molecules to specific sites in the body.

A hydrocarbon is a compound that contains carbon and hydrogen atoms only. Most compounds in crude oil are hydrocarbons.

Crude oil is a complex mixture of many different hydrocarbon compounds. It formed over millions of years from the remains of dead organisms buried under high pressure and temperature. It is a finite resource.

What is the general formula for alkanes, and what does it mean?

The general formula for alkanes is C n H 2n+2 , where n is the number of carbon atoms. For example, with n = 1: CH 4 (methane); n = 2: C 2 H 6 (ethane). Alkanes are saturated — they have only single carbon-carbon bonds.

The first four alkanes in order are: .......... (CH 4 ), .......... (C 2 H 6 ), .......... (C 3 H 8 ), and .......... (C 4 H 10 ).

The first four alkanes in order are: methane (CH 4 ), ethane (C 2 H 6 ), propane (C 3 H 8 ), and butane (C 4 H 10 ).

True or False? Crude oil is a pure substance made entirely of one type of hydrocarbon.

False. Crude oil is a mixture of a very large number of different hydrocarbon compounds. This is why it must be separated by fractional distillation before the individual components can be used.

Why is crude oil described as a finite resource ?

Crude oil is described as finite because it is being used up much faster than it can be formed. It took millions of years to form from the remains of ancient organisms, so once reserves are exhausted they cannot be replaced on a human timescale.

True or False? Alkanes are described as saturated hydrocarbons because they contain carbon-carbon double bonds.

False. Alkanes are saturated because they contain only single carbon-carbon bonds. Hydrocarbons with carbon-carbon double bonds are called alkenes and are described as unsaturated .

Define fractional distillation .

Fractional distillation is the process used to separate crude oil into groups of hydrocarbons with similar chain lengths, called fractions . It exploits the different boiling points of hydrocarbons depending on chain length.

Explain how fractional distillation separates crude oil into its fractions.

Crude oil is heated and the vapours enter a fractionating column with a temperature gradient (hot at the bottom, cooler at top) Hydrocarbons with high boiling points condense and are collected near the bottom Hydrocarbons with lower boiling points rise higher and condense nearer the top Each fraction collected contains hydrocarbons of similar chain length

True or False? Larger hydrocarbon molecules have lower boiling points than smaller hydrocarbon molecules.

False. Larger hydrocarbon molecules have higher boiling points because they have stronger intermolecular forces , requiring more energy to overcome. Smaller molecules have lower boiling points and rise to the top of the fractionating column .

As hydrocarbon chain length increases, boiling point .......... , viscosity .......... , and flammability ........... .

As hydrocarbon chain length increases, boiling point increases , viscosity increases , and flammability decreases .

Name four useful fuels produced from crude oil and give a use for each.

Petrol — fuel for cars Kerosene — jet fuel Diesel — diesel engines Heavy fuel oil — ships and power stations (Also: liquefied petroleum gas for domestic heating/cooking)

True or False? Fractional distillation is a chemical process that creates new molecules from crude oil.

False. Fractional distillation is a physical process — it separates existing hydrocarbon molecules by exploiting their different boiling points . No new molecules are created; the chemical identities of the hydrocarbons remain unchanged.

Why does crude oil need to be separated before it can be used?

Crude oil is a mixture of many different hydrocarbons with varying properties (boiling points, viscosities, flammabilities). Separating it into fractions produces groups of hydrocarbons with consistent properties suitable for specific uses such as fuels or feedstocks .

What are the products of complete combustion of a hydrocarbon?

Complete combustion of a hydrocarbon (in a plentiful oxygen supply) produces carbon dioxide and water : hydrocarbon + oxygen → carbon dioxide + water

Define complete combustion .

Complete combustion occurs when a hydrocarbon burns in a plentiful supply of oxygen , producing only carbon dioxide and water . All the carbon is fully oxidised to CO 2 .

True or False? The complete combustion of methane produces carbon monoxide and water.

False. The complete combustion of methane produces carbon dioxide and water: CH 4 + 2O 2 → CO 2 + 2H 2 O Carbon monoxide is produced during incomplete combustion when there is insufficient oxygen.

Petrochemical products obtained from crude oil include fuels, .......... , .......... , solvents, and ........... .

Petrochemical products obtained from crude oil include fuels, polymers , lubricants , solvents, and detergents .

Why do car exhaust fumes contain carbon monoxide even though petrol undergoes combustion?

Car engines do not provide a sufficient oxygen supply for complete combustion of all the petrol. This results in incomplete combustion , producing carbon monoxide (and unburnt hydrocarbons) alongside carbon dioxide and water.

What is the balanced symbol equation for the complete combustion of methane, CH 4 ?

CH 4 + 2O 2 → CO 2 + 2H 2 O Carbon and hydrogen from the methane are both oxidised: carbon forms carbon dioxide and hydrogen forms water .

True or False? The combustion of hydrocarbons in vehicles is a major source of carbon dioxide, contributing to global warming.

True. Carbon dioxide from the combustion of hydrocarbon fuels in vehicles is a major contributor to the greenhouse effect and global warming . This is a key reason for the push towards electric vehicles.

Cracking is an industrial process that breaks long-chain hydrocarbon molecules into shorter, more useful molecules. It produces alkanes (used as fuels) and alkenes (used to make polymers and other chemicals).

State the conditions used for catalytic cracking .

In catalytic cracking , the hydrocarbon vapours are heated to high temperatures and passed over a hot powdered catalyst . The catalyst lowers the activation energy needed to break the covalent bonds in the hydrocarbon chains.

True or False? The products of cracking include alkanes and alkenes.

True. Cracking breaks long-chain alkanes into a mixture of shorter alkanes and alkenes . The alkenes contain carbon-carbon double bonds (C=C) and are unsaturated , making them more reactive and useful as starting materials for polymers.

Hexane (C 6 H 14 ) is cracked to form butane (C 4 H 10 ) and .......... (C 2 H 4 ). The equation is: C 6 H 14 → C 4 H 10 + ...........

Hexane (C 6 H 14 ) is cracked to form butane (C 4 H 10 ) and ethene (C 2 H 4 ). The equation is: C 6 H 14 → C 4 H 10 + C 2 H 4

Why is cracking economically important?

There is greater demand for short-chain hydrocarbons (e.g. petrol, diesel) than can be supplied directly from crude oil refining. Cracking converts the excess long-chain fractions into shorter, more commercially valuable products, balancing supply and demand.

An alkene is an unsaturated hydrocarbon with the general formula C n H 2n . Alkenes contain at least one carbon-carbon double bond (C=C), making them more reactive than alkanes. They are produced by cracking.

What is the difference between catalytic cracking and steam cracking ?

Catalytic cracking : hydrocarbon vapours are passed over a hot catalyst. Steam cracking : vaporised hydrocarbons are mixed with steam at high temperature. Steam cracking produces more alkenes and hydrogen.

True or False? In a cracking equation, the number of carbon and hydrogen atoms must balance on both sides.

True. By the law of conservation of mass , cracking is a chemical reaction where atoms are rearranged but not created or destroyed. The total number of carbon atoms and hydrogen atoms must be the same in the reactant(s) and products.

GCSEScienceAQACombined Science: SynergyPhysical SciencesFlashcardsGuiding Spaceship Earth Towards a Sustainable FutureCarbon Chemistry

Carbon Chemistry (AQA GCSE Combined Science: Synergy: Physical Sciences): Flashcards

Exam code: 8465

1/37

0Still learning

Know0

FrontBonding & Structure In Forms Of Carbon
Define allotrope.

Was this flashcard helpful?

Cards in this collection (37)

Define allotrope.
An allotrope is one of two or more different structural forms of the same element. Diamond, graphite, graphene, and fullerenes are all allotropes of carbon.
Why does diamond not conduct electricity?
In diamond, each carbon atom forms four covalent bonds to other carbon atoms, using all its outer electrons. There are no delocalised (free) electrons to carry a charge, so diamond cannot conduct electricity.
True or False?
Graphite can conduct electricity because it has delocalised electrons between its layers.
True.
In graphite, each carbon atom forms only three covalent bonds, leaving one free (delocalised) electron per carbon atom. These electrons can move between the layers and carry charge, allowing graphite to conduct electricity.
Why is graphite soft and slippery, making it useful as a lubricant?
Graphite is arranged in layers. Within layers, carbon atoms are held by strong covalent bonds, but between layers there are only weak intermolecular forces. These allow the layers to slide over each other easily, giving graphite its soft, slippery properties.
Define graphene.
Graphene is a single layer of graphite — a one-atom-thick sheet of carbon atoms arranged in a hexagonal lattice. It is extremely strong, flexible, transparent, and conducts electricity due to delocalised electrons.
Fullerenes are molecules of carbon atoms with .......... shapes. The first fullerene discovered was .........., which contains .......... carbon atoms and has a .......... shape.
Fullerenes are molecules of carbon atoms with hollow shapes. The first fullerene discovered was Buckminsterfullerene, which contains 60 carbon atoms and has a spherical shape.
State two uses of carbon nanotubes.
Carbon nanotubes are used in:
1. Nanotechnology and electronics — due to high electrical conductivity
2. Composite materials — due to their high tensile strength and low density
True or False?
Fullerenes can be used in targeted drug delivery because they can trap other molecules inside their hollow structures.
True.
Fullerenes have hollow, cage-like structures that can trap other molecules inside them. This makes them useful for delivering drug molecules to specific sites in the body.
Define hydrocarbon.
A hydrocarbon is a compound that contains carbon and hydrogen atoms only. Most compounds in crude oil are hydrocarbons.
Define crude oil.
Crude oil is a complex mixture of many different hydrocarbon compounds. It formed over millions of years from the remains of dead organisms buried under high pressure and temperature. It is a finite resource.
What is the general formula for alkanes, and what does it mean?
The general formula for alkanes is C_nH_2n+2, where n is the number of carbon atoms. For example, with n = 1: CH₄ (methane); n = 2: C₂H₆ (ethane). Alkanes are saturated — they have only single carbon-carbon bonds.
The first four alkanes in order are: .......... (CH₄), .......... (C₂H₆), .......... (C₃H₈), and .......... (C₄H₁₀).
The first four alkanes in order are: methane (CH₄), ethane (C₂H₆), propane (C₃H₈), and butane (C₄H₁₀).
True or False?
Crude oil is a pure substance made entirely of one type of hydrocarbon.
False.
Crude oil is a mixture of a very large number of different hydrocarbon compounds. This is why it must be separated by fractional distillation before the individual components can be used.
Why is crude oil described as a finite resource?
Crude oil is described as finite because it is being used up much faster than it can be formed. It took millions of years to form from the remains of ancient organisms, so once reserves are exhausted they cannot be replaced on a human timescale.
True or False?
Alkanes are described as saturated hydrocarbons because they contain carbon-carbon double bonds.
False.
Alkanes are saturated because they contain only single carbon-carbon bonds. Hydrocarbons with carbon-carbon double bonds are called alkenes and are described as unsaturated.
Define fractional distillation.
Fractional distillation is the process used to separate crude oil into groups of hydrocarbons with similar chain lengths, called fractions. It exploits the different boiling points of hydrocarbons depending on chain length.
Explain how fractional distillation separates crude oil into its fractions.
1. Crude oil is heated and the vapours enter a fractionating column with a temperature gradient (hot at the bottom, cooler at top)
2. Hydrocarbons with high boiling points condense and are collected near the bottom
3. Hydrocarbons with lower boiling points rise higher and condense nearer the top
4. Each fraction collected contains hydrocarbons of similar chain length
True or False?
Larger hydrocarbon molecules have lower boiling points than smaller hydrocarbon molecules.
False.
Larger hydrocarbon molecules have higher boiling points because they have stronger intermolecular forces, requiring more energy to overcome. Smaller molecules have lower boiling points and rise to the top of the fractionating column.
As hydrocarbon chain length increases, boiling point .........., viscosity .........., and flammability ............
As hydrocarbon chain length increases, boiling point increases, viscosity increases, and flammability decreases.
Name four useful fuels produced from crude oil and give a use for each.
1. Petrol — fuel for cars
2. Kerosene — jet fuel
3. Diesel — diesel engines
4. Heavy fuel oil — ships and power stations
(Also: liquefied petroleum gas for domestic heating/cooking)
True or False?
Fractional distillation is a chemical process that creates new molecules from crude oil.
False.
Fractional distillation is a physical process — it separates existing hydrocarbon molecules by exploiting their different boiling points. No new molecules are created; the chemical identities of the hydrocarbons remain unchanged.
Why does crude oil need to be separated before it can be used?
Crude oil is a mixture of many different hydrocarbons with varying properties (boiling points, viscosities, flammabilities). Separating it into fractions produces groups of hydrocarbons with consistent properties suitable for specific uses such as fuels or feedstocks.
What are the products of complete combustion of a hydrocarbon?
Complete combustion of a hydrocarbon (in a plentiful oxygen supply) produces carbon dioxide and water:
hydrocarbon + oxygen → carbon dioxide + water
Define complete combustion.
Complete combustion occurs when a hydrocarbon burns in a plentiful supply of oxygen, producing only carbon dioxide and water. All the carbon is fully oxidised to CO₂.
True or False?
The complete combustion of methane produces carbon monoxide and water.
False.
The complete combustion of methane produces carbon dioxide and water:
CH₄ + 2O₂ → CO₂ + 2H₂O
Carbon monoxide is produced during incomplete combustion when there is insufficient oxygen.
Petrochemical products obtained from crude oil include fuels, .........., .........., solvents, and ............
Petrochemical products obtained from crude oil include fuels, polymers, lubricants, solvents, and detergents.
Why do car exhaust fumes contain carbon monoxide even though petrol undergoes combustion?
Car engines do not provide a sufficient oxygen supply for complete combustion of all the petrol. This results in incomplete combustion, producing carbon monoxide (and unburnt hydrocarbons) alongside carbon dioxide and water.
What is the balanced symbol equation for the complete combustion of methane, CH₄?
CH₄ + 2O₂ → CO₂ + 2H₂O
Carbon and hydrogen from the methane are both oxidised: carbon forms carbon dioxide and hydrogen forms water.
True or False?
The combustion of hydrocarbons in vehicles is a major source of carbon dioxide, contributing to global warming.
True.
Carbon dioxide from the combustion of hydrocarbon fuels in vehicles is a major contributor to the greenhouse effect and global warming. This is a key reason for the push towards electric vehicles.
Define cracking.
Cracking is an industrial process that breaks long-chain hydrocarbon molecules into shorter, more useful molecules. It produces alkanes (used as fuels) and alkenes (used to make polymers and other chemicals).
State the conditions used for catalytic cracking.
In catalytic cracking, the hydrocarbon vapours are heated to high temperatures and passed over a hot powdered catalyst. The catalyst lowers the activation energy needed to break the covalent bonds in the hydrocarbon chains.
True or False?
The products of cracking include alkanes and alkenes.
True.
Cracking breaks long-chain alkanes into a mixture of shorter alkanes and alkenes. The alkenes contain carbon-carbon double bonds (C=C) and are unsaturated, making them more reactive and useful as starting materials for polymers.
Hexane (C₆H₁₄) is cracked to form butane (C₄H₁₀) and .......... (C₂H₄). The equation is: C₆H₁₄ → C₄H₁₀ + ...........
Hexane (C₆H₁₄) is cracked to form butane (C₄H₁₀) and ethene (C₂H₄). The equation is: C₆H₁₄ → C₄H₁₀ + C₂H₄
Why is cracking economically important?
There is greater demand for short-chain hydrocarbons (e.g. petrol, diesel) than can be supplied directly from crude oil refining. Cracking converts the excess long-chain fractions into shorter, more commercially valuable products, balancing supply and demand.
Define alkene.
An alkene is an unsaturated hydrocarbon with the general formula C_nH_2n. Alkenes contain at least one carbon-carbon double bond (C=C), making them more reactive than alkanes. They are produced by cracking.
What is the difference between catalytic cracking and steam cracking?
Catalytic cracking: hydrocarbon vapours are passed over a hot catalyst.
Steam cracking: vaporised hydrocarbons are mixed with steam at high temperature. Steam cracking produces more alkenes and hydrogen.
True or False?
In a cracking equation, the number of carbon and hydrogen atoms must balance on both sides.
True.
By the law of conservation of mass, cracking is a chemical reaction where atoms are rearranged but not created or destroyed. The total number of carbon atoms and hydrogen atoms must be the same in the reactant(s) and products.

Sign up to unlock flashcards

By signing up you agree to our Terms and Privacy Policy

Previous:Atoms into Ions & Ions into AtomsNext:Resources of Materials & Energy