chemistry notes

Chem notes

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Julian Smilg LTJA Sunday, 31 May 2009
Chemistry revision notes
States of matter:
Solids have a regular shape, the particles are packed in a regular pattern. Solids
cannot be compressed, the particles are as close together as they can possibly
get. Solids are dense, there is very little space between the particles
Liquids take up the shape of the bottom of a container in which you place them, the
particles are not in any fixed position. Liquids are very difficult to compress, as the
particles cannot get much closer. Liquids are quite dense, there is not much
empty space between the particles.
Gases have no shape, they fill up whatever space is available as theparticles move
rapidly around in all directions.Gases are easily compressed, the particles have
large spaces between them, so it is easy to push them closer together.Gases have
very low densities, there are huge amounts of space between particles.
When a solid is heated, its particles gain more energy and vibrate more. Due to the
increase in vibrations, the solid expands. At melting point, the particles vibrate so
much that they break away from their positions. It is at this point that a solid
becomes a liquid.
When a liquid is supplied with heat, its particles gain more energy and therefore move
around quicker. This increase in movement causes the liquid to expand. At boiling
point the liquid particles gain enough energy to overcome the forces holding them
together these particles break away from one another and the liquid now becomes
a gas.
Not all particles in a liquid contain the same amount of energy some have more!
This is why evaporation of a liquid can take place below its boiling point. This is called
evaporation and explains why puddles dry up on sunny days.
When you cool a gas, the particles lose energy. This loss in energy causes the
particles to move more slowly as they move closer together. When the particles no
longer have sufficient energy to move away as they bump into one another the gas
becomes a liquid.

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When a liquid is cooled, the particles once more lose energy, they vibrate less as they
slow down. Eventually they stop moving, except for vibrations in fixed positions. A
solid has now formed.
The diffusion of gases
The lighter the particles of gas, the faster the gas will diffuse.
Dissolved substances have to pass through the cell membrane to get into or out of a cell.
Diffusion is one of the processes that allows this to happen.
Diffusion occurs when particles spread.…read more

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Some of the groups have special names:
Group 1: the alkali metals.
Group 2: the alkaline earth metals.
Group 7: the halogens.
Group 0 or 8: the noble gases.
The zigzag line through the Periodic Table separates the Metals on the left
with the nonmetals to the right of the line.
The Periods
The horizontal rows are called Periods.
Period 3 contains Sodium(Na), Magnesium(Mg), Aluminium(Al), Silicon(Si),
Phosphorus(P), Sulphur(S), Chlorine(Cl) and Argon(Ar).
The Periods represent the energy shell these atoms outer electrons are located
within.…read more

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At the centre of an atom is a nucleus containing protons and neutrons. Electrons are arranged
around the nucleus in energy levels or shells. Make sure you can label a simple diagram of an
atom like this one.
The number of protons in the nucleus is called the atomic number.
For sodium (Na) the atomic number is 11.
The atomic number tells you what the element is (see the periodic table).
The atomic number of an element never changes.
Mass Number.…read more

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As you go down Group 1 the atoms become larger and the outer electron is further from the
nucleus. The force of attraction between the positively-charged nucleus and the
negatively-charged outer electron becomes weaker, which is why the outer electron is more
easily lost.
So potassium is more reactive than lithium because the outer electron of a potassium atom is
further from its nucleus than the outer electron of a lithium atom.
Francium atoms, with 7 shells, are the largest atoms in Group 1.…read more

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Chemical formula
The chemical formula of a compound shows how many of each type of atom join together to
make the units that make the compound up. For example, in iron sulfide every iron atom is joined
to one sulfur atom, so we show its formula as FeS. In sodium oxide, there are two sodium atoms
for every oxygen atom, so we show its formula as Na2O. Notice that the 2 is written as a
subscript, so Na2O would be wrong.…read more

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1. We CAN put numbers in front of symbols/ formula
2. We CANNOT change formula
3. We CANNOT put numbers in the middle of formulae.
Prep and tests for gasses, test for water
Gases such as hydrogen, oxygen, carbon dioxide, ammonia and chlorine can be made using
chemical reactions. These gases are collected in different ways, depending upon their density
and solubility in water. They can be identified using different tests.…read more

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Iron and steel rust when they come into contact with water and oxygen. Both water and oxygen
are needed for rusting to occur. In the experiment below, the nail does not rust when air -
containing oxygen - or water is not present:
Calcium chloride absorbs water in the right-hand test
Salt dissolved in water does not cause rusting, but it
does speed it up, as does acid rain.
Aluminium does not rust - corrode.…read more

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The process of removing sulfur dioxide
Sulfur can be removed from fuels at the oil refinery. This makes the fuel more expensive to produce, but it
prevents sulfur dioxide being produced. You may have noticed 'low sulfur' petrol and diesel on sale at filling
Greenhouse effect
The greenhouse effect
When fossil fuels are burnt - by industry, in power stations and in vehicles and planes - the
gases enter the atmosphere.…read more

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E Magnesium
A Aluminium
C Zinc
T Iron
I Nickel
V Tin
T Lead
Y Copper
Platinum…read more


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