Unit 5a chemistry

This is all the content for this topic.

HideShow resource information
Preview of Unit 5a chemistry

First 253 words of the document:

Unit 5a - Fuels
Oil is the source of many fuels and this section deals with their uses.
Pollution resulting from burning these fuels is also considered.
Energy in Everyday Life
Energy is used to provide electricity, heating, lighting and cooking
for homes as well as the power necessary to allow industry to
Burning Substances
Burning is a chemical reaction, to combine with oxygen, in which
energy (mainly heat) is released - this kind of reaction is called an
exothermic reaction.
Combustion is another word for burning. A fuel is a substance which
burns in oxygen giving out heat.
The opposite of an exothermic reaction is an endothermic reaction
0 one in which energy is taken in during the reaction.
A Chemical Reaction
Air is a mixture of gases. The two main gases in air are oxygen (O2)
and Nitrogen (N2).
Oxygen - 20% , Nitrogen - 80%.
Oxygen reacts with a fuel when it burns.
Oxygen relights a glowing splint.
Your breath contains oxygen which helps things to burn.
The safest way to put out a chip pan is to cover it with a damp cloth
to stop oxygen getting at the fire.
For a substance to burn, heat and oxygen is required (i.e. for a fire
you need heat, oxygen and a fuel).
The test for the presence of oxygen:

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

Oxygen gas is produced when potassium permanganate is heated.
Fossil Fuels
A fossil fuel is a fuel which has been made under the earth from
natural living things millions of years ago.
Extreme heat and pressure turn them into fossil fuels.
In the beginning their energy came from the sun. Example of fossil
fuels are coal, oil and natural gas.…read more

Page 3

Preview of page 3

Here's a taster:

It is important to conserve our resources of coal, oil and gas as some
day they will run out.
Alternative sources to these fuels are - nuclear, tidal/wave,
hydro-electric, solar and wind.
A finite energy source is not renewable - it will not last forever.
Renewable energy sources are sources which can be replaced and
we can use them all the time.
Coal, Oil and Gas are finite energy sources.
Nuclear, tidal/wave, hydro-electric, solar and wind are renewable
(infinite) energy sources.…read more

Page 4

Preview of page 4

Here's a taster:

Ethanol boils at 79'c, water boils at 100'c. If we heat the tube until
the temperature reaches about 85'c, the ethanol will boil but the
water will remain as a liquid.
Crude Oil
Crude oil is a thick dark liquid which is a mixture of different liquids
with different boiling points. To be useful this thick dark syrup must
be separated into a number of fractions. This separation process is
called Fractional Distillation.…read more

Page 5

Preview of page 5

Here's a taster:

Properties of Crude Oil Fractions
1. Colour - The lightest fractions are very pale coloured but this
darkens as the boiling point increases.
2. Ease of Evaporation - The lightest fraction evaporates most easily -
it contains the smallest, lightest molecules.
3. Flammability - This is the same as burning. The lightest fractions
burn most easily. It is easier for the air to penetrate, mix and ignite.
4. Viscosity - This means the thickness of the oils.…read more

Page 6

Preview of page 6

Here's a taster:

These two compounds have different formulae and although they
are both colourless invisible gases, they are as different as life and
Carbon monoxide (CO) has a formula which does not obey the
valency rules for working out formulae.
You will just have to learn its name and formula.
Carbon monoxide is made by the incomplete combustion of either
Carbon or a fuel containing Carbon.…read more

Page 7

Preview of page 7

Here's a taster:

When carbon or a carbon-containing fuel burns in air, the carbon
reacts with the Oxygen in the air to form Carbon dioxide.
When there is a limited supply of Oxygen to burn the fuel, as in a
petrol or diesel car engine, the product of the reaction is carbon
The two oxides are quite different.…read more

Page 8

Preview of page 8

Here's a taster:

Air contains harmful pollutants. These arise mainly from the
burning of fossil fuels. Waste products from vehicle engines and coal
burning power stations cause most pollution.
In a Vehicle Engine
If a fuel is not burned completely to carbon dioxide, carbon
monoxide and unburnt petrol are released from the exhaust.
Carbon monoxide attaches itself to the haemoglobin in our blood
and stops it transporting oxygen around our bodies.…read more

Page 9

Preview of page 9

Here's a taster:

Food + Oxygen ---> Water Vapour + Carbon Dioxide
{the Reactants}......{the Products}
In a word equation:
I) the + sign means 'reacts with' or 'and'.
ii) The ---> sign means 'to produce'.
iii) The reactants come in front of the arrow; the produces come
after the arrow.
State Symbols
Suffixes can be used after the name or formula to show the physical
state of the substances.
Suffix: (s), Meaning: Solid.
Suffix: (l), Meaning: Liquid.
Suffix (g), Meaning: Gas.…read more


No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all resources »