Crude Oil And Fuels(mark Scheme)

Question 1

What is a mixture?

Answer 1

A mixture consist of two or more elements or compounds not chemically combined together. The chemical properties of each substance In the mixture are unchanged. It is possible to separate the substances in a mixture by physical methods including distillation

Question 2

What do most compounds in crude oil consist of?

Answer 2

Most of the compounds in crude oil consist of molecules made up of hydrogen and carbon atoms only (hydrocarbons). Most of these are saturated hydrocarbons called alkanes.

Question 3

What is the general formula for alkanes?

Answer 3

CnH2n+2

Question 4

Who are alkane molecules represented?

Answer 4

C2H6

       H   H
        l    l
H - C - C - H
       l     l 
      H    H

Question 5

Who can the hydrocarbons in crude oil be seperated?

Answer 5

They can be separated into fractions, each of which contains molecules with a similar number of carbon atoms, by evaporating the oil and allowing it to co dense at a number if different temperature. This process is fractional distillation

Question 6

What do some of the properties in hydrocarbons depend on?

Answer 6

The size of the molecules. These properties influence how hydrocarbons are used as fuels

Question 7

Why are most fuels, including coal, bad for the environment?

Answer 7

Because they contain carbon and/or hydrogen and may also contain some sulfur.
The gases is released into the atmosphere when a fuel is burnt  my include harmful gases (CO2-global warming and sulfur dioxide and oxides of nitrogen-acid rain) and water (vapour) and carbon monoxide.
Solid particles (particulates) may also be released causing global dimming.

Question 8

What happens in the combustion of hydrocarbon fuels?

Answer 8

Energy is released. During combustion the carbon and hydrogen in the fuels oxidises

Question 9

When can sulfur be removed?

Answer 9

It can be removed from fuels before they are burned, for example in vehicles.

Question 10

When can sulfur dioxide be removed?

Answer 10

It can be removed from waste gases after combustion, for example in power stations.

Question 11

How are biofuels , such as biodiesel and ethanol, produced?

Answer 11

From pant materials

Question 12

What are ethical issues surrounding the use of biofuels?

Answer 12

There are ethical issues surrounding the use of biofuels. For example, crops that could be used to feed people are used to provide the raw materials for biofuels instead. This could cause food shortages or increases in the price of food.

Question 13

What are economic issues surrounding the use of biofuels?

Answer 13

human resources -more people are needed to produce biofuels than are needed to produce petrol and diesel
increased income - for farmers
lower fuel prices - biofuels limit the demand for fossil fuels, helping to reduce increases in fuel prices.

Question 14

What are environmental issues surrounding the use of biofuels?

Answer 14

Biodiesel naturally contains little sulfur. For example, it may be said that they are carbon neutral – the amount of carbon dioxide released when they are used is the same as the amount absorbed by the plants as they grew. If so, this would reduce the production of this greenhouse gas.
However, while biofuels produce less carbon dioxide overall, they are not carbon neutral. This is because fossil fuels are used in their production, for example in making fertilisers for the growing plants

Question 15

What is crude oil?

Answer 15

A mixture of a very large number of compounds

Question 16

Name the type of reaction that releases energy from a fuel

Answer 16

Exothermic