SC20 Fuels

Question 1

Define hydrocarbon

Answer 1

A compound made of hydrogen and carbon and is used as a raw material

Question 2

Why is crude oil finite?

Answer 2

It’s formed underground over millions of years from the buried remains of plants and animals

Question 3

Top Fraction - Gases

Answer 3

used in domestic heating and cooking

Question 4

2nd Fraction from top - Petrol

Answer 4

used as fuel in cars

Question 5

3rd Fraction from top - Kerosene

Answer 5

used as a fuel in aircraft

Question 6

4th Fraction from top - Diesel

Answer 6

used as a fuel in some cars and larger vehicles eg. trains

Question 7

5th Fraction - Fuel oil

Answer 7

used as a fuel for larger ships and power stations

Question 8

6th Fraction - Bitumen

Answer 8

used to surface roads and roofs

Question 9

How does fractional distillation work?

Answer 9

Crude oil is heated until most of it has turned to gas. The gases enter a fractionating column with a temp. gradient. The longer hydrocarbons have high bps so turn into liquids and drain out the bottom

Question 10

Why do properties of different fractions differ?

Answer 10

Each fraction has a different length of hydrocarbons, so they each have different properties because of this

Question 11

Define homologous series

Answer 11

A family of molecules with the same general formula and share similar chemical properties

Question 12

Why do alkanes form a homologous series?

Answer 12

They all share the same general formula, with a difference of CH2

Question 13

Define complete combustion

Answer 13

Burning hydrocarbons with plenty of oxygen to produce CO2 and water

Question 14

Define incomplete combustion

Answer 14

Occurs when a hydrocarbon is burnt with a limited supply of oxygen

Question 15

Why is carbon monoxide toxic?

Answer 15

It combines with red blood cells and stops your blood from carrying oxygen around the body. This can cause fainting, a coma or even death

Question 16

Problems with incomplete combustion

Answer 16

It produces carbon monoxide, and carbon in the form of soot

Question 17

How are harmful products made in incomplete combustion?

Answer 17

Without enough oxygen, the products contain less oxygen, which forms toxic products

Question 18

How is sulfur dioxide made?

Answer 18

When fossil fuels are burned, they release sulfur dioxide which comes from sulfur impurities in the fossil fuels.

Question 19

What causes acid rain?

Answer 19

When sulfur dioxide mixes with the clouds, forming dilute sulfuric acid

Question 20

Effects of acid rain

Answer 20

Causes lakes to become acidic and animals to die. Kills trees, damages limestone buildings and stone statues, and can also make metal corrode

Question 21

Define oxides of nitrogen

Answer 21

Created from a reaction between the nitrogen and oxygen in the air, caused by the energy released by combustion reactions

Question 22

What do oxides of nitrogen cause?

Answer 22

Contribute to acid rain, and cause photochemical smog that causes air pollution

Question 23

Advantages to using Hydrogen as a fuel

Answer 23

• Clean fuel
• Only waste product is water
• Renewable

Question 24

Disadvantages to using Hydrogen as a fuel

Answer 24

• Need a special, expensive machine
• Expensive
• Uses energy from other sources (energy often from burning fossil fuels)

Question 25

Define cracking

Answer 25

Cracking turns long saturated alkane molecules into smaller unsaturated alkene and alkane molecules - it’s a form of thermal decomposition

Question 26

Why are alkanes saturated and alkenes unsaturated?

Answer 26

Alkanes are saturated because all bonds have been formed. Whereas alkenes are unsaturated because all possible bonds that can be formed, haven’t been

Question 27

Why is cracking necessary?

Answer 27

Cracking helps meet the higher demand for shorter chained molecules, rather than having longer chained molecules that aren’t commonly needed