Download Faster or Slower 2!

Most paints have three main parts:
- pigment (the coloured part)
- binding medium (like a glues, sticks it to the wall)
- solvent (thins the paint to make it easier to use)
Colloids:
Colloids are mixtures of tiny particles dispersed within
another, they are NOT DISSOLVED. Paints are colloids,
because they have small solid particles of pigment dispersed
within binding medium.
Pigments:
We used to make pigments by grinding down different
rocks. Now we use synthetic pigments which are brighter and
last for longer.
Oil Paint:
Oil paint contains pigment, a solvent and oil as the
binding medium.
Oil paint dries when the solvent evaporates, leaving
the oil and pigment. The oil, as the binding medium, dries
forming a skin and sticks the pigment to the painted
surface. The oil dries by chemical reaction.
But the evaporating solvent is also a pollutant....
Manufacturers try to reduce the amount of pollution in their
paint. One way to do this is to use emulsion paint.
Emulsion Paint:
Emulsions contain less solvent. It is basically the
same as oil paint, except it is dispersed within water (as oil
and water do not mix). Therefore, emulsion paints are
colloids in two ways: they have pigment dispersed with oil,
and then that oil dispersed in water.
When emulsion paint dries, the water evaporates
leaving the oil droplets behind, which join together to make
a continuous film.
Thermochromic Paints:
These paints change colour at certain temperature.
They normally change from coloured to colourless, but can
be painted over other colours to make different colours.
Thermochromic paints can be used in cups etc, to
show when they are too hot.
Phosphorescent Paints:
Phosphorescent paints are glow in the dark paints,
that absorb the energy from daylight, and then slowly
release this energy as light.
We used to use radioactive paints in watch dials,
until the manufacturers started to develop cancer!
C2 B – Construction
Materials
Raw Materials
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Most modern buildings are made of materials dug
out of the earth.
Limestone, marble and granite are used in
buildings.
Limestone is a sedimentary rock. This type of
rock is made by fragments settling into layers.
Marble is a metamorphic rock. This means the
rock has been changed. In the case of marble, it
is a form of limestone which has been subjected
to heat and pressure making it harder than
original limestone.
Granite is an igneous rock. Igneous rock is
formed out of liquid rock that cools slowly and
forms interlocking crystal as it solidifies. The
Cement and Concrete
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Cement is made from limestone which is a form
of calcium carbonate. When the calcium
carbonate is heated it thermally decomposes to
form calcium oxide and carbon dioxide.
Cement, sand and gravel mixed with water and
left to set is called concrete.
Quarries can cause dust pollution, damaged
landscape and take up a lot of space.
If the quarries were not there then the land could
be used as a rubbish tip, covered with soil and
planted with trees or left to fill with water and
used for sailing and fishing.
More on Thermal
Decomposition
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Thermal decomposition is the chemical
breakdown of a compound into at least two other
compounds under the effect of heat.
Calcium carbonate thermally decomposes at a
high temperature.
CaCO3
CaO + CO2
Calcium carbonate
calcium oxide +
carbon dioxide
Reinforced Concrete
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Concrete is very strong under compression. It is
much weaker under tension.
Steel is strong under tension.
Steel rods are inserted into concrete reinforcing
them.
The steel rods stop the concrete from stretching
under tension.
Grade B
Grade A
Key points to remember about the structure of the
Earth.
Tectonic plates move very slowly in
different ways
-The outer layer is called the lithosphere
-Apart
-It is made of the crust and part of the
mantle underneath.
- The tectonic plates are less dense than the mantle
and ‘float’ on it.
-Two kinds of plates
-Continental plates carry continents
-Oceanic plates that lie underneath
oceans
Crust is too thick for anyone to drill through it – yet.
Most knowledge comes from measuring seismic
waves produced by Earthquakes.
-Collide
-Scrape sideways past each other
Energy from the hot core is transferred
to the surface by slow convection
currents in the mantle.
Early explanations for the movement of
tectonic plates was that they were
dragged by convecting mantle like a
conveyer belt. Now they think that it is
more complicated.
Grade A
Subduction
The two types of tectonic plates
have different densities.
-Oceanic plates are more dense
than continental plates and sink
low down into the mantle. Oceans
accumulate on top of them.
-Continental plates float high up in
the mantle.
When two plates collide the more
dense oceanic plate sinks below the
less dense continental plate. This is
called subduction.
Subduction zones are where plates
are being destroyed
The oceanic plate partially re-melts and is
reabsorbed into the mantle. Some of the
molten rock works its way back up the surface
and creates a chain of volcanoes.
The subducting oceanic plate does not move
smoothly; it slips at intervals. When it slips the
vibrations cause earthquakes.
Grade B
Magma rises through the Earth’s crust
because it is less dense. It then cools and
solidifies into igneous rock either after it
comes out of a volcano as lava, or before it
even gets to the surface.
Igneous rocks have different crystal
structures.
-Small crystals- it has cooled rapidly (close to
the surface)
-Large crystals – it has called slowly (further
from the surface and better insulated)
Example of
rock type
Small
crystal
Large
crystal
Iron-rich
magma
Basalt
Gabbro
Silica-rich
magma
Rhyolite
Granite
Grade A
Magma and volcanoes
Iron-rich magma
- Or basaltic magma tends to be runny.
- Fairly ‘safe’
- Lava spills over edges of volcano and people
who live near it can get away.
Silica-rich magma
-Less runny
-Erupts quietly or explosively
-Dissolved gases in the magma have no time to
escape from the stiff liquid
-Shoots out clouds of hot ash and pumice
-Rain turns ash into mudslides
-Falling ash could include volcanic bombs
Geologists investigate past
eruptions by looking at ash
layers.
In each eruption, course ash falls
first followed by fine ash,
producing graded bedding
Future eruptions can sometimes
be predicted with the help of
seismometers. This method is not
precise and disasters still occur.
Metals and Alloys
• Copper is easily recyclable as it melts down easily.
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Copper must be sorted carefully before recycling so
different grades of copper aren’t mixed. Coper
must first be analysed before recycling.
Impure copper has to be electrolysed before it can
be used in areas where pure copper is needed, like
electrical wiring.
In the purification of copper we use a copper
sulfate electrolyte and copper electrodes: The
anode is made of impure copper and the cathode
of pure. The anode dissolves in the electrolyte and
the cathode is plated in pure copper.
The cathode is a thin sheet of pure copper, this
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Most metals form alloys. Alloys have lower melting points
than the pure metal.
Bronze is an alloy of copper and tin. It’s harder than copper
and shrinks slightly when it solidifies so it is easy to cast.
Steel contains iron. Stainless steels are much stronger than
pure iron and they do not rust.
Nitinol is a smart alloy made from nickel and titanium. Smart
alloys can change shape at different temperatures, this is
called shape memory.
Smart alloys have a number of uses, one of which is a
showerhead that reduces the water supply if the water gets
too hot that it may cause damage.
Cars For Scrap
Rust is a brownish solid that forms
when oxygen and water, which are
needed for the reaction to happen,
react with iron or steel.Salt water and
acid rain speed up the reaction of
rusting.
Rust is a chemical reaction between
iron, oxygen and water. The chemical
name for the product is Hydrated
Iron(III) Oxide. This is a type of
reaction called oxidation because the
iron reacts with oxygen to make an
oxide.
Iron and aluminium
• Pure iron and pure aluminium aren’t very strong so
they are made into alloys. An alloy is a mixture of a
metal and another element, for example steel is a
mixture of iron and carbon. Often an alloy is a
mixture of metals.
• Old cars are often dumped and taken to a scrap yard
where their parts get recycled.
• Iron and aluminium can be separated from each other
because iron is magnetic but aluminium isn’t. In the
scrap yard the car body is cut into smaller pieces, then
an electromagnet attracts the iron and steel parts.
• Recycling makes sense because:
– It reduces the amount of rubbish that goes into landfill
sites
– It avoids environmental damage (mining and quarrying)
– Aluminium and iron are finite sources so they will
eventually run out
Different materials in cars are
used for different reasons:
Material and its use
Reasons material is
used
Aluminium in car bodies and wheel
hubs
Does not corrode, less density,
malleable, quite strong
Iron or steel car bodies
Malleable, strong
Copper in electrical wires
Ductile, good electrical
conductor
Lead in lead-acid batteries
Conducts electricity
Plastic in dashboards, dials, bumpers Rigid, does not corrode, cheap
PVC in metal wire coverings
Flexible, does not react with
water, electrical insulator
Glass and plastic/glass composite in
windscreens
Transparent, shatterproof
Fibre in seats
Can be woven into textiles, can
be dyed, hard-wearing
Iron vs Aluminium
• Iron is stronger and
harder which is
important in a crash.
• Iron is cheaper to make
a car body out of.
Property
Aluminium
Iron
Corrosion in
moist air
No obvious
corrosion
Rusts
rapidly
Density in
g/cm)2
2.7
7.9
Melting
point in
degrees
celsius
660
1527
Boiling point
in degrees
celsius
2467
2750
Magnetism
Not
attracted to
a magnet
Attracted to
a magnet
• Aluminium-bodied cars
have a better fuel
economy than a similar
car made from iron
• Aluminium is more
malleable than iron
• Aluminium doesn’t
corrode as easily as
iron, so has a much
longer lifetime.
• Aluminium is less dense
than iron so the mass of
the car body is less than
one made of iron.
Clean air
Clean air is made up of 78% nitrogen, 21% oxygen
and 1% other (containing carbon dioxide). These do
not change often because of the balance between
processes that use carbon dioxide and produce
oxygen and vice versa. These processes are in the
carbon cycle
Clean air
If the composition of the air changes then it is due to the
factors; increased energy usage, increased population
and deforestation.
This is the theory of the evolution of the atmosphere; first
of all the original gases came from the centre of the
earth in a process called degassing, the original gases
were ammonia and carbon dioxide, then the ammonia
reacted with rocks to produce nitrogen and water, the
percentage of nitrogen increased and because it is
unreactive very little was removed from the atmosphere,
then photosynthesising organisms evolved and produced
oxygen, as the amount of oxygen increased the carbon
dioxide percentage decreased until the atmosphere of
today's levels were reached.
Clean air
These are some pollutants in the atmosphere.
Pollutant
Where it comes from
Environmental effects
Carbon monoxide
Incomplete combustion
Poisonous gas
Oxides of nitrogen Reaction of nitrogen and oxygen
in internal combustion engines
Photochemical smog,
acid rain
Sulfur dioxide
Acid rain
Combustion of fossil fuels with
sulfur impurities
Catalytic converters are used to reduce the amount of the pollutants.
Catalytic converter
Carbon monoxide
hydrocarbons
oxides of nitrogen
Not fitted
5.59
1.67
1.04
Fitted
0.61
0.07
0.04
Clean air
Catalytic converters contain a rhodium catalyst.
A reaction between nitric oxide and carbon
monoxide contain takes place on the surface
of the catalyst the reaction forms nitrogen and
carbon dioxide.
Carbon monoxide + nitric oxide = nitrogen + carbon dioxide
2CO
+ 2NO
= N2
+ 2CO2
Faster or Slower [1]
Explosions:
•Are caused by chemical reactions
•Very fast reaction that makes lots of gas
•The force of the explosion is caused by the gas molecules moving away from the centre
Speed of Reaction:
•Reactants are made into products during chemical reactions
•Chemical reactants take place when particles collide with each other
•The speed of a reaction can be controlled by the:
* Concentration of the reactants
* Pressure of reactants that are gases
* Temperature of the reactants
* Surface area of the reactants
When any of these factors are increased the rate of reaction will also be increased as the
particles either move faster, have less room to move in, have a bigger area to collide with or
have more particles to collide with and all of these factors create more successful collisions
per second.
Simple collision Theory:
• The more successful collisions there are per second the faster the process of the reaction.
• For a successful collision to occur the particles must be moving very fast ad have a lot of
kinetic energy.
Diagram B represents the fastest chemical reaction process in both of these examples:
A = has a lower concentration B = has a higher concentration
A = has a lower temperature B = has a higher temperature
(the arrows on B show that the particles are moving faster)
A = has lower pressure B = has higher pressure
A = has a smaller surface area B = has a larger surface area
(a magnifying glass showing that the particles have a larger surface area)
Note:
It isn’t the number of collision that determines the rate of reaction it is
the collision frequency.
The more successful collisions per second the faster the reaction.
Measuring the rate of Reaction:
Most chemical reactions are hard to measure. Magnesium and dilute hydrochloric acid are
easier to measure than others.
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During the reaction the magnesium fizzes in the dilute hydrochloric acid and bubbles are
given off.
The hydrogen released in the bubbles is then recorded in a gas syringe every few seconds.
Magnesium + Hydrochloric acid > Magnesium chloride + Hydrogen
The reaction time is the time taken for the magnesium to begin to react and the amount of
bubbles released.
When the reaction is over no more gas is made and one of the reactants is used up.
C2G.
Faster or Slower 2!
Some factories use combustible powders such as:
o Sulfur
o Flour
o Custard Flour
o Wood Dust
o Trinitrotoluene (TNT)
They must be extremely careful because if the powders reach
the open atmosphere they can potentially explode.
They must make certain that the chance of producing a spark
is very small. Therefore reducing the risk of ignition.
Mwah haha, I wonder
what will happen to my
special combustible
power is I set it
alight??........
Faster or Slower 2
A powder has a much larger surface area than
a block or lump of reactant.
As the surface of a solid , the rate of reaction
also .
When a substance is in a big lump fewer
reacting particles can be in contact with the
reacting particles of a different substance.
Whereas, if a powder reacts with another
substance more reacting particles can be in
contact. As the surface are increases there are
more particles colliding with each other. This
means there are more successful collisions per
second.
Successful collisions = when two chemicals
collide and produce a chemical reaction.
It is the collision frequency between
reactant particles that is important in
determining how fast a reaction takes
place. The more successful collisions there
are the faster the reaction takes place.
When the surface area of a solid reactant
increases there will be even more collisions
every second. This means that the rate of
reaction has increased.
Reactions can happen at different speeds.
Rate of reaction can be increased by
temperature, concentration, pressure of
particles and a larger surface area. These
all help a reaction to speed up meaning
more successful collisions per second.
Faster or Slower 2!
A catalyst is a substance
added to a chemical
reaction to make the
reaction go faster. A
catalyst does not change
how much a product is
made. A catalyst will never
change as it is not part of
the reaction. A catalyst is
extremely useful when
making chemicals. When
a catalyst is added to a
reaction it speeds it up
vastly.
A catalyst increases the rate of reaction.
Some other properties of a catalyst are:
it is unchanged at the end of a reaction
only a small mass of catalyst is needed
to have an effect over a
large mass if reactants
One catalyst is specific to a
specific chemical reaction.
This is because they are
certain shapes so only the
reactants in a certain chemical
reaction fit a specifically
designed catalyst.
The time taken
for a reaction
to finish can
be longer or
shorter, but not faster or
slower.
Catalysts get particles
in the correct orientation
for a reaction. This
means collisions
need less energy
to be successful.
Faster or Slower 2!
Most catalysts only make a
specific reaction faster. They
are not made for all types of
chemical reactions. Copper
catalyses the reaction between
zinc and dilute sulfuric acid, but
it will not catalyse other
reactions. Unfortunately, this
means that scientists have had
to research and discover
hundreds of different catalysts
for us to use in different
reactions. Examples of these
are:
 zeolites or aluminium oxide in
the cracking of long-chained
hydrocarbons.
 rhodium-based catalysts in a
catalyst converter.
 the use of vanadium oxide in
manufacturing sulfuric acid.
FACT:
CFC’s produce chlorine
atoms when they
slowly break down the
atmosphere which are
catalysing the
destruction of our
atmospheric ozone.
A catalyst does not
increase the number of
collisions per second.
Instead it works by
making the collisions
that take place more
successful.
It helps reacting
particles collide with the
correct orientation.
Causing a faster
reaction.
It also allows collisions
between particles with
less kinetic energy than
average to be
successful.