Chemistry, C2

year 11 exam for science unit 2

this is for double science. NOT triple unless you want to read them too :)


  • Coloured rock (pigment) particles (colour)
  • Solvent (evaporates)
  • Binding medium (sticks)

Paint is a colloid, small particles are dispersed through the whole liquid, but aren't dissolved! solid particles in a liquid. scattered through mixture as small enough not to settle

OIL PAINT- solvent evaporates leaving bm to dry and form a skin, this sticks the p to the surface. Oil in this is sticky and takes long time to harden. solvent has evaporated oil reacts slowly with oxygen in air to form a tough flexible film over the wood. the oil bm is oxidised in air

EMULSION PAINT- water-based paint (tiny droplets of liquid in water)-when applied to a surface as a thin layer, the water evaporates leaving the bm and p. As this dries it joins together to make a continuous film.

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  • used in paints that are chosen for their colour and also for the temperature at which their colour changes.
  • Change from a colour to colourless
  • Limited range of colours. larger range by mixing with normal acrylic paint.


  • Aborb energy and store it
  • Release it slowly as light
  • much safer than radioactive paints (were used for glow in the dark)
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Building Materials

manufactured rocks

  • brick clay
  • glass-sand
  • aluminium or iron - their ores

igneous and metamorphic rock harder than sedimentary rocks.

granite-igneous- fromed from liquid rock that cools slowly and forms interlocking( this structure gives hardness) crystal as it solidifies

marble-metamorphic-rock has been under heat and pressure in earths crust making it harder than the original rock

limestone-sedimentary- shells of dead sea-creatures stuck together

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Building materials continued

Thermal decomposition-chemical breakdown of a compound into at least 2 other compounds under the effect of heat.

when limestone is heated to thermally decompose it, 1 substance changes into 2: calcium carbonate --> calcium oxide +carbon dioxide.


Reinforced concrete- steel rods/meshes running through it , stronger than concrete. Composite material.

better construction material than non-reinforced concrete.

Steel is strong under tension. these stop the concrete from stretching

concrete- compression strong, tension weak (will crack)

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  • copper and zinc to make brass
  • lead and tin to make solder

Metals from cars are easy to recycle. Plastics need legislation.

aluminium doesn't corrode in moist conditions, as it has a protective layer of aluminium oxide which doesn't flake on the surface.

Alloys are pure metals mixed with other elements have properties that make them more useful than the pure metal. For example steel is harder and stronger than iron.

Iron and aluminium are used for cars . Iron rusts, aluminium doesn't. Rusting is the oxidation of iron to form hydrated iron oxide.

Impure copper can be purified in the laboratory using an electrolysis cell. the anode is impure copper and dissolves into the electrolyte. Cathode is 'plated' with new copper.

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made of tectonic plates- these float on the mantle(as they're less dense than the mantle). plates are moving all the time.

If molten rock cools slowly the crystals that are formed are bigger

subduction zones- where the plates are being destroyed.

  • continental plates- carry continents
  • oceanic plates- lie underneath the oceans

Lithosphere- consists of the crust and outer part of the mantle. It is the relatively cold outer part of the Earth’s structure.

  1. crust - relatively thin and rocky
  2. mantle - has the properties of a solid, but can flow very slowly
  3. outer core - made from liquid nickel and iron
  4. inner core - made from solid nickel and iron
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used to be poisonous, but then plants produced oxygen.

Compostion of the atmosphere is now:

21% oxygen and 78% nitrogen

carbon dioxide is given out in combustion, but taken in during photosynthesis.

Originally came from gases escaping from the interior of the Earth.

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Fast or slow

Rates of reaction are affected by:

  • Temperature
  • Surface area
  • Concentration
  • Catalysts

An increase in surface area of a reactant increases the frequency of collisions

The higher the temperature the faster the particles move. This increases the rate of reaction

Collision frequency- NOT the number of collisions, is the number of successful collisions between reactant particles each second. for a successful collision each particle must have lots of kinetic energy.

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Rates of reaction


Extrapolation- extending the graph to read it

Interpolation- reading the graph within between closer points

Rate of reaction can be worked out from the gradient of a graph, which can be found by drawing construction lines

  • Choose part of graph where theres a straight line (not a curve)
  • Measure the value of y and x
  • Divide y by x
  • The gradient of the graph is: gradient= y over x

rate of reaction = total amount of reactant used or product made ÷ time taken

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Fast or slow continued

during an explosion, large volume of gaseous products are released, moving outwards from the reaction at great speed causing the explosion effect.

Combustible powders often cause explosions. powder reacts with oxygen make large volumes of CO2 and water vapour. Have to be careful, cannot reach open atmosphere, as this might produce a spark.

Powered reactant have much larger surface area, than the same mass of a block of reactant. As the surface area of a solid reactant increases so does the rate of the reaction.

A catalyst

  • needed in small quantities to catalyse a large mass or reactants
  • is unchanged at the end of a reaction
  • usually only makes a specific reaction faster
  • doesn't increase the collisions per second
  • works by making collisions more successful
  • helps reacting particles collide with the correct orientation
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