Using resources 3 Flashcards
Ceramics/composites/polymers, The Haber process, NPK fertilisers
What are ceramics?
Non- metal solids with high melting points but that are NOT made from carbon-based compounds.
How are clay ceramics made?
Shaping wet clay and then heating in a furnace.
What is clay’s ability to be moulded when wet and hardened when fired at high temps useful for?
Making pottery and bricks.
Name ceramics.
-Clay
-Glass
Properties of glass
Glass is generally transparent, can be brittle when thin, and can be moulded when hot.
What is most of the glass we use?
Soda-lime glass.
How is soda-lime glass made?
By heating a mixture of sand, sodium carbonate and limestone until it melts.
When the mixture cools, it comes out as glass.
Which type of glass has a higher melting point than soda-lime glass?
Borosilicate glass.
How is borosilicate glass made?
By heating a mixture of sand and boron trioxide until it melts.
When the mixture cools, it comes out as glass.
What do the properties of polymers depend on?
-What monomers they are made from
-The conditions under which they are made
Which 2 polymers are produced from ethene?
Low density (LD) and high density (HD) poly(ethene).
Low density poly(ethene).
-Made from ethene at a moderate temperature under a high pressure
-It’s flexible, so used in bags and bottles
High density (HD) poly(ethene).
-Made from ethene at a lower temperature and pressure
-With a catalyst
-It’s more rigid so used for water tanks and drainpipes
Which type of polymers melt when heated?
Thermosoftening polymers.
Which type of polymers do not melt when heated?
Thermosetting polymers.
Explain what thermosoftening polymers are in terms of their structures.
Thermosoftening polymers contain individual polymer chains joined by weak intermolecular forces, allowing the plastic to be melted and remoulded.
Explain what thermosetting polymers are in terms of their structures.
(On the other hand)
Thermosetting polymers contain monomers which form cross-links between the polymer chains and hold the chains together in a solid structure.
Unlike thermosoftening polymers, they don’t soften when heated.
Instead, they are strong, hard and rigid.
What are cross-links?
Covalent bonds found between the polymer chains in thermosetting polymers.
What are composite materials?
Materials consisting of two or more materials with DIFFERENT properties, that have been combined to produce a material with more DESIRABLE properties.
What two materials are most composites made of?
-Reinforcement
-Matrix
What is the reinforcement? (composites)
Fibres or fragments of a material.
What is the matrix? (composites)
Usually something that starts soft and then hardens.
It binds the reinforcement together.
Describe the structure of a composite material.
Most composites are made of two materials:
A matrix which surrounds and binds together fibres/ fragments of the other material (which is called the reinforcement).
Name some composite materials.
Fibreglass
Carbon fire
Concrete
Wood
Fibreglass
Fibres of glass bound by a matrix made of plastic (a polymer).
Fibreglass properties
-Low density like plastic
-Very strong like glass
Fibreglass uses
-Skis
-Boats
-Surfboards
Carbon fibre
Long chains of carbon atoms, or carbon nanotubes, bound by a matrix made of plastic (a polymer).
Carbon fibre properties
-Strong
-light
Carbon fibre uses
-Aerospace
-Sports car manufacturing
What is concrete made from?
Aggregate (a mixture of sand and gravel) embedded in cement.
This makes it very strong, so is ideal for use as a building material.
What is wood?
A natural composite made from cellulose fibres held together by an organic polymer matrix.
You need to be able to compare quantitatively the physical properties of which materials?
Glass and clay ceramics, polymers, composites and metals.
Properties of ceramics?
-Insulators of heat and electricity
-Brittle
-Stiff
Properties of polymers?
-Insulators of heat and electricity
-Flexible
-Malleable
Applications of polymers?
Used in clothing/insulators/electrical items.
Properties of composites?
Depends on the matrix and reinforcement used to make them, so they have many different uses.
Properties of metals?
-Malleable
-Good conductors of heat and electricity
-Shiny
-Stiff
-Ductile (can be drawn into wires)
Uses of metals?
Used in cutlery/electrical wires/car body-work and more.
When given a ‘compare’ question, what must we do?
Make a judgement on which material/method is better.
What is the name of the process used to manufacture ammonia?
The Haber process
What can ammonia be used to produce?
Nitrogen-based fertilisers.
What are the reactants/’raw materials’ for the Haber process?
-nitrogen
-hydrogen
What raw material is hydrogen obtained from in the Haber process?
Natural gas
What raw material is nitrogen obtained from in the Haber process?
The air
Describe the Haber process.
1- Nitrogen and hydrogen (can list the source) are pumped into a compressor
2-The purified gases are passed over a catalyst of iron at a high temperature and a high pressure
3-Some of the hydrogen and nitrogen reacts to form ammonia.
4- On cooling, the ammonia liquefies and is removed.
5- The unreacted hydrogen and nitrogen are recycled back into the compressor
What type of reaction is the Haber process?
reversible
Why is the Haber process reversible?
Some of the ammonia produced breaks down into nitrogen and hydrogen.
Give the word equation for the Haber process.
nitrogen + hydrogen ⇌ ammonia
Give the symbol equation for the Haber process
N₂ (g) + 3H₂ (g) ⇌ 2NH₃ (g)
Is the reaction of hydrogen and nitrogen to form ammonia endothermic or exothermic?
Exothermic.
The reaction produces heat energy.
Interpret graphs of reaction conditions versus rate.
Practice question time! (if at home x)
What is the trade-off in the Haber process between:
-rate of production
-position of equilibrium
The trade-off is between increasing the rate whilst maximising the yield.
EXPLAIN the trade-off in the Haber process between:
-rate of production
-position of equilibrium
-The forward reaction is exothermic so lower temperatures would shift the position of equilibrium to the right and increase yield
-But higher temperatures mean a faster rate of reaction (so equilibrium reached more quickly)
-So 450°C is a COMPROMISE between maximum yield and the rate of reaction.
What temperature is used for the Haber process?
450°C
What pressure is used for the Haber Process?
200 atmospheres.
What is the pressure of 200 atm a compromise between in the Haber process
-High yield and rate of reaction
-Cost and danger to build & maintain
Why is a high pressure good in the Haber process?
-There are four molecules on the lhs for every 2 molecules on the rhs
-So, increasing pressure shifts the equilibrium to the rhs
-This maximises the percentage yield
Why is an iron catalyst used in the Haber process?
To increase the rate of reaction (without affecting the yield!)
What are the commercially used conditions for the Haber process related to?
-Thee availability and cost of raw materials and energy supplies
-The control of equilibrium position and rate
Which three elements do NPK fertilisers contain?
nitrogen
phosphorus
potassium
What are compounds of nitrogen, phosphorus and potassium used as?
Fertilisers - to improve agricultural productivity, increasing yield.
Why are formulated fertilisers better than manure?
Formulated fertilisers are more widely available, easier to use, don’t smell, and have enough of each nutrient to grow more crops
What happens if plants don’t get enough of N, P, or K?
-Stunted growth
-Life processes affected e.g. reproduction
Out of interest, what can a potassium deficiency lead to?
Poor fruit development and quality.
Why might the elements N, P and K be missing from the soil?
If they’ve been used up by a previous crop.
How can the industrial production of NPK fertilisers can be achieved?
Using a variety of raw materials in several integrated processes.
What ARE NPK fertilisers? like what actually are they?
Formulations of various salts (N, P, K salts) containing appropriate percentages of the elements.
Why is the addition of nitrogen to the soil beneficial for plants?
Nitrogen is combined with carbon to form amino acids, which are built into proteins. This helps plants to grow (faster).
What can ammonia be used to manufacture?
-ammonium salts
-nitric acid
What is the chemical symbol for ammonia?
NH₃
What is ammonia reacted with to make nitric acid?
Oxygen and water.
(in a series of reactions).
What is ammonia reacted with to produce ammonium salts?
Acids
Ammonia + Nitric acid → ?
Ammonium nitrate (NH₄NO₃ (aq) )
Give the symbol equation for the formation of ammonium nitrate.
NH₃ (aq) + HNO₃ (aq) → NH₄NO₃ (aq)
Why is NH₄NO₃ (ammonium nitrate) an especially good compound for use in a fertiliser?
It has nitrogen from two sources.
You may be asked to compare the INDUSTRIAL production of NH₄NO₃ (ammonium nitrate) with what?
The LABORATORY preparation of NH₄NO₃.
Describe the industrial production of NH₄NO₃ (ammonium nitrate)
In giant vats, high concentrations, very exothermic.
Heat released is used to evaporate water from the mixture = a very concentrated NH₄NO₃ product.
Describe the laboratory production of NH₄NO₃ (ammonium nitrate)
Smaller scale, by titration and then crystallisation to give pure NH₄NO₃ crystals.
Reactants in a lower conc, so less heat produced = safer.
Why is crystallisation not used in industry?
It’s very slow.
How is potassium chloride obtained?
By mining.
How is potassium sulfate obtained?
By mining.
How is phosphate rock obtained?
By mining.
What can potassium chloride and potassium sulfate be directly used as?
Fertilisers.
Can potassium rock be used directly as a fertiliser?
NO.
Why can’t phosphate rock be used directly as a fertiliser?
The phosphate salts in the rock are insoluble so plants can’t absorb them by active transport.
What does reacting phosphate rock with an acid produce?
A soluble phosphate (that plants CAN absorb by active transport and use as nutrients).
Name the products produced when phosphate rock reacts with nitric acid.
-Phosphoric acid
-Calcium nitrate (the salt!)
Name the products produced when phosphate rock reacts with sulfuric acid.
-Calcium sulfate
-Calcium phosphate
(both salts)
What is the mixture of calcium sulfate
and calcium phosphate known as?
Single superphosphate.
Name the products produced when phosphate rock reacts with phosphoric acid.
-Calcium phosphate
(also known as triple superphosphate)
