Fuels and Hydrocarbons Flashcards Preview

Nat 5 Chemistry > Fuels and Hydrocarbons > Flashcards

Flashcards in Fuels and Hydrocarbons Deck (37)
Loading flashcards...
1
Q

What is a fuel?

A

A fuel is a substance that produces energy when burnt.

2
Q

What is combustion?

A

Combustion is another word for burning. It is n exothermic reaction that gives out heat.

3
Q

What three things are required to keep a fire going?

A

Oxygen, heat, fuel.

4
Q

What are the three main sources of fuel?

A

Coal, crude oil [oil] and gas.

5
Q

What is a finite source?

A

A finite source is something that runs out with time.

6
Q

How is coal formed?

A

300 million years ago, giant plants died in swamps. Over millions of years these plants were buried under water and dirt. Heat and pressure turned the dead plants into coal.

7
Q

How is crude oil and gas formed?

A

Around 400 million years ago, tiny sea plants and animals died and were buried on the ocean floor. Over time, they were covered by sand and silt rocks. The heat and pressure turned them into crude oil and gas. Today we drill down through the layers of sand and silt rocks to reach the oil and gas.

8
Q

What are hydrocarbons made of?

A

Hydrogen and carbon.

9
Q

What do hydrocarbons produce when they react with oxygen?

A

Carbon Dioxide and water.

10
Q

What is the test for carbon dioxide?

A

It turns lime water milky/cloudy.

11
Q

What is the test for water?

A

It turns blue cobalt chloride paper pink.

12
Q

Pollution Problems - When is carbon monoxide formed?

A

It is formed when there is not enough oxygen to burn the hydrocarbons completely. It is toxic, but it is odorless and colourless.

13
Q

Pollution Problems - When is soot formed?

A

Incomplete combustion causes soot particles. It is black and can cause breathing difficulties, asthma and even cancer.

14
Q

How can you reduce pollution?

A

1) Removing sulphur from fuels.
2) Adding a transition metal [platinum/rhodium] catalytic converter to engines, which changes toxic emissions into harmless gases.

15
Q

How is crude oil separated?

A

Fractional distillation.

16
Q

What is distillation?

A

A method of separating a mixture of liquids by boiling points.

17
Q

Define viscosity.

A

The ability for a liquid to flow.
Eg. Low viscosity - Runny liquid like water.
High viscosity - Sticky liquid like syrup.

18
Q

Define flammability.

A

How easily the substance ignites.
Low boiling point - highly flammable.
High boiling point - burns with difficulty.

19
Q

What are the properties of methane?

A

Clear, colourless and odorless gas [smell is added for safety].
Insoluble in water.
Highly explosive and burns in air.
pH of 7 - neutral.

20
Q

What are alkanes?

A

A family of hydrocarbons that contain only single covalent bonds between the atoms of hydrogen and carbon.

21
Q

What are saturated hydrocarbons?

A

Hydrocarbons with all single bonded carbon atoms.

22
Q

What is the general formula for alkanes?

A

Cn H2n+2 where n is the number of carbon atoms.

23
Q

What does the homologous series display?

A
  • Similar chemical properties.
  • Gradual trend of physical properties.
  • Can all be represented by a general formula.
24
Q

What are isomers?

A

Compounds with the same molecular formula but different structural formulae.

25
Q

What are cycloalkanes?

A

Family of hydrocarbons in which the carbon atoms are in a ring and have single bonds between them.

26
Q

What is the general formula for cycloalkanes?

A

Cn H2n where n is the number of carbon atoms.

27
Q

What are alkenes?

A

Family of hydrocarbons that contains one double bond between two carbon atoms [the rest are single bonds].

28
Q

What are unsaturated hydrocarbons?

A

Hydrocarbons with one or more double bonds.

29
Q

What is cracking?

A

Cracking is a process that produces a mixture of saturated and unsaturated hydrocarbons.

30
Q

Where do plastic come from?

A

Most plastics come from crude oil - specifically from the naphtha fraction.

31
Q

Why do we use plastic?

A

Plastics are: flexible, waterproof, shatterproof, lightweight, and easy to shape/mould.

32
Q

What are thermoplastics?

A

Plastics that soften or melt when heated. Can be made into another shape.

33
Q

What are thermosetting plastics?

A

Plastics that do not soften when heated. Cannot be made into other shapes

34
Q

What are the toxic gases that plastics give off when they are burnt?

A

Carbon monoxide, hydrogen cyanide, hydrogen chloride, dioxin.

35
Q

What are polymers?

A

A very large chain of molecules made by joining together many monomers.

36
Q

What are monomers?

A

Small molecules that join together to form polymers through polymerisation.

37
Q

What is polymerisation?

A

The process in which a polymer is formed.