C1 Exhaustive Revision Notes

These are my exhaustive revision notes for Chemistry Unit 2 of the GCSE Science / GCSE Chemistry syllabus for Edexcel.

I have used multiple textbooks as well as internet sources to compile these notes, and whilst I was compiling them, I actively kept the syllabus at hand, so hopefully there is nothing beyond these notes which is essential knowledge in order to answer any question on the exam paper (I would promise, but I know everyone's liable to human error!).

HideShow resource information
Preview of C1 Exhaustive Revision Notes

First 571 words of the document:

The composition of the Earths atmosphere, which is the layer of gases surrounding the Earth, has changed
over millions of years.
When the Earth was first formed 4.6 billion years ago, the surface was molten for many years, with intense
volcanic activity for the first billion years. These erupted frequently to release carbon dioxide, nitrogen and
water vapour .
Resultingly, it is thought that the early atmosphere, much like modern-day Mars or Venus, contained:
little or no oxygen
a lot of carbon dioxide (10 to 200 times todays levels)
small amounts of water vapour, ammonia
and methane .
Scientists have to rely on informed guesswork to suggest how the Earth s early atmosphere may have been like,
often simply comparing the Earth to nearby planets and moons with less developed atmospheres such as Mars,
Venus and Titan, the largest moon of Saturn.
Despite this, there is evidence for the above suggestions in how volcanoes release carbon dioxide but little
oxygen and in how iron compounds found in the Earths oldest rocks could only have been formed in the absence
of oxygen.
Eventually, the Earths surface cooled so that the water vapour released from the volcanoes could condense
into water. Concurrently, the Earths surface s
olidifiedenough in order for the water to form the oceans.
After the oceanswere formed, the proportion of c
arbon dioxide in the E
arths atmosphere decreased because:
the carbon dioxide dissolved into the o
later marine organisms incorporated the dissolved carbon dioxide into their anatomy (like molluscs, coral
and starfish for shells)
deceased marine organisms became part of s edimentary rocks .
At the same time as the proportion of carbon dioxide in the Earth s atmosphere decreased, the proportion of
oxygen in the Earth s atmosphere increased because primitive photosynthesising plants used atmospheric
carbon dioxide to release atmospheric oxygen. Such primitive plants were only able to be supported because of
the water in the oceans.
Atmospheric and oceanic oxygen levels increased dramatically in the late Proterozoic, between 700 and 550
million years ago, as more complex plants evolved due to the huge availability of carbon dioxide. As
photosynthesis took place, the ozone layer (composed of O3) was formed, which enabled even more complex life
forms to evolve, including animals.
The proportion of oxygen in the Earths atmosphere can be measured through a simple investigation in which a
known volume of airis passed over excess hot copperacross two gas syringes.
The oxygen in the air will react with the excess hot cooper between the gas syringes to form copper dioxide
when the gas syringe containing the air is pushed completely. The percentage of oxygen in the Earths
atmosphere is then the subtraction of the final volume of air in the second gas syringe from the original volume
of airin the first gas syringe , divided by the original v
olume of a irin the first gas syringe and multiplied by 100.
Usually, dry air is used to indicate the proportion of gases in the contemporary Earths atmosphere. Dry air
excludes water vapour because the proportion of it in dry air varies daily.
Gas Formula n in dry
Nitrogen N2 78%
Oxygen O2 21%
Argon Ar 0.9%

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

CO 0.04%
dioxide 2
n/a traces
In the above table, the class "other gases" includes the inert noble gases, carbon monoxide,methane and
sulphur dioxide.
Nitrogen gas is prominent in the contemporary Earths atmosphere, and it is theorised to have come from
volcanoesin the Earths early atmosphere.
Small changes in the composition of the E
arthsatmospherecan occur through natural and human activities.…read more

Page 3

Preview of page 3

Here's a taster:

In order to reduce global warming , scientists are investigating two geoengineering methods to reduce the
proportion of carbon dioxidein the atmosphere .
Firstly, scientists are adding iron compounds to the oceans , a process known as iron seeding . Iron is essential
for plant growth, so it is hoped that by increasing the amount of iron in the oceans , more aquatic plants such as
algae can grow.…read more

Page 4

Preview of page 4

Here's a taster:

The incomplete combustion of any hydrocarbon is dangerous, especially domestically. Carbon monoxide is an
odourless, colourless, toxic gas and the c
arbonproduced (
soot) can be dangerous too.
Carbon monoxide enters ones bloodstream after inhalation and mixes with haemoglobin in red blood cells to
form carboxyhaemoglobin , which stops the red blood cells from being able to carry oxygen around the body,
thereby depriving respiring cells of oxygen and causing body cells and tissues to die.…read more

Page 5

Preview of page 5

Here's a taster:

These factors considered, the production of biofuels requires considerable amounts of land which may result in
less land for farmland, thereby reducing the worldwide supply of food and increasing food prices. In addition,
this land could be obtained through deforestation , a major contributor to global warming.
Another alternative to fossil fuels being considered by scientists is hydrogen.…read more

Page 6

Preview of page 6

Here's a taster:

Sedimentary rocks are susceptible to containing the fossils of deceased marine organisms that have sunk to the
seabed, and are more susceptible to erosion than igneous and metamorphic rocks because they do not contain
crystals and are layered, so there are few interlocking bonds to keep the s
edimentary rock together.…read more

Page 7

Preview of page 7

Here's a taster:

(hydrogen )
Platinum .
Resultingly, copper carbonate thermally decomposes easier than zinc carbonate, which in turn thermally
decomposes easier than calcium carbonate :
Carbonate Temperature required for thermal decomposition
Calcium carbonate 825 o
Zinc carbonate 300 o
Copper carbonate 200 o
The productsof the thermal decomposition of calcium carbonateare carbon oxide and carbon dioxide.…read more

Page 8

Preview of page 8

Here's a taster:

In all of the above chemical reactions, the a
cid is neutralisedto produce a salt.
Hydrochloric acid produces chloride salts nitric acid produces nitrate salts and sulphuric acid produces
Hydrochloric acid is produced naturally in the stomach in order to activate the digestive enzyme pepsin for
digestionand to kill off any microorganisms as a chemical barrier of the immune system.…read more

Page 9

Preview of page 9

Here's a taster:

Chlorine gas is a yellow-green toxic gas, meaning that there is a potential hazard in its large-scale manufacture
through any leaks of it in factories or during its transportation, which may lead to the death of individuals.
Chlorine gas is used in making bleach and in making the polymer poly(chloroethene) (PVC ). Because it is toxic to
living organisms, it is also used in manufacturing disinfectants and in swimming pools in order to kill bacteria.…read more

Page 10

Preview of page 10

Here's a taster:

Iron or steel cans coated with tin do not make use of sacrificial protection: the tin only acts as a barrier
between the iron or steeland the air,
but is itself less reactive than the i
ron or steel.
Other methods of corrosion prevention include oiling, greasing and painting, all of which work through
preventing the metal from making contact with airor w
Metals are non-renewable resources.…read more


No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all resources »