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Keywords : Alloy, carbon steels, low-alloy steels, high-alloy steels

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Properties of iron & steels. Prior Learning: Identify & explain different extraction processes. Keywords : Alloy, carbon steels, low-alloy steels, high-alloy steels. Learning Objectives: By the end of the lesson I can:. • The properties of pig iron and how this limits its usefulness. - PowerPoint PPT Presentation

Text of Keywords : Alloy, carbon steels, low-alloy steels, high-alloy steels

Slide 1GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
Teacher notes
This completing sentences activity provides the opportunity for some informal assessment of students’ understanding of metal extraction. Students could be asked to write down the missing words in their books and the activity could be concluded by completion on the IWB
21.unknown
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
Keywords:
Prior Learning:
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
Learning Objectives:
By the end of the lesson I can:
• The properties of pig iron and how this limits its usefulness.
Pig iron is the intermediate product of smelting iron ore with coke. Pig iron has a very high carbon content, typically 3.5–4.5%, which makes it very brittle and not useful directly as a material except for limited applications.
• That iron can be alloyed to make it more useful.
• Explain how the properties of alloys (but not smart alloys) are related to models of their structures.
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
What are the properties of different metals?
Teacher notes
This image represents various properties of metals, including:
gold (Au): This metal is unreactive. This is represented by having the band on stage, not mixing with the other elements and not doing very much.
lead (Pb), zinc (Zn) and copper (Cu): These metals are heavy metals and are dressed up as heavy metal rockers.
copper (Cu): This metal has been drawn into wires.
aluminium (Al) and titanium (Ti): These metals are reactive. In this scene, they are getting overexcited and knocking over a table.
iron (Fe): This metal has rust patches and is struggling to lift the bar stools.
steel (Fe wearing ‘nerves of steel’ T shirts): These metal alloys have carbon atoms on their shoulders to show that they are alloys. The steel is shinier than the iron atom. Steel is easily lifting the bar stools that iron was unable to lift because it is stronger.
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
gold (Au): This metal is unreactive. This is represented by having the band on stage, not mixing with the other elements and not doing very much.
lead (Pb), zinc (Zn) and copper (Cu): These metals are heavy metals and are dressed up as heavy metal rockers.
copper (Cu): This metal has been drawn into wires.
aluminium (Al) and titanium (Ti): These metals are reactive. In this scene, they are getting overexcited and knocking over a table.
iron (Fe): This metal has rust patches and is struggling to lift the bar stools.
steel (Fe wearing ‘nerves of steel’ T shirts): These metal alloys have carbon atoms on their shoulders to show that they are alloys. The steel is shinier than the iron atom. Steel is easily lifting the bar stools that iron was unable to lift because it is stronger.
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
Let’s go back in time 3 years to Year 7
YEAR 10
YEAR 7
And draw (or make a model to show) the atom arrangement in a solid
Now add a different sized particle to your model. What is this called?
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
What are the general properties of most metals?
solid at room temperature
high melting point
malleable: they can be shaped
ductile: they can be drawn into wires
strong
dense
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
sea of electrons
metal ions
The atoms in a pure metal are in tightly-packed layers, which form
a regular lattice structure.
The outer electrons of the metal atoms separate from the atoms
and create a ‘sea of electrons’.
These electrons are delocalized and so are free to move through
the whole structure.
The metal atoms become positively charged ions and are attracted to the sea of electrons. This attraction is called metallic bonding.
Teacher notes
Please note that this diagram is not drawn to scale. It should be stressed to students that an electron is tiny compared to a metal ion, especially the solid nucleus of a metal ion. This means that the electrons are able to pass between the metal ions.
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
How does the sea of electrons affect the properties of metals?
Teacher notes
This illustration represents some key features of metallic bonding including:
The metal ions (represented by the brown spherical characters) are standing very close together. This can be used to remind students of the tightly-packed arrangement of ions that occurs in metallic structures. It could also be mentioned that the metal ions are in a happy, holiday mood: they are positive ions.
The metal ions are surrounded by sea. This represents the sea of electrons found in metallic bonding. Students should be aware that it is the strong attraction between the positively charged ions and the negatively charged sea of electrons that gives metals their properties of strength and high melting and boiling points. The sea of electrons is also able to move freely around the closely packed metal ions. This enables metals to conduct heat and electricity.
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
Delocalized electrons in metallic bonding allow metals to conduct heat and electricity.
This makes heat transfer in metals very efficient.
Delocalized electrons also conduct electricity through metals in a similar way.
For example, when a metal is heated, the delocalized electrons gain kinetic energy.
These electrons then move faster and so transfer the gained energy throughout the metal.
heat
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
Metals are usually strong, not brittle. When a metal is hit, the layers of metal ions are able to slide over each other, and so the structure does not shatter.
The metallic bonds do not break because the delocalized electrons are free to move throughout the structure.
metal after it is hit
force
force
This also explains why metals are malleable (easy to shape) and ductile (can be drawn into wires).
metal before it is hit
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
Teacher notes
This true-or-false activity could be used as a plenary or revision exercise to test students’ understanding of metallic bonding. Students could be given coloured traffic light cards (green=true, red=false) to vote on the statements shown.
31.unknown
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
Investigating Alloys
What will you change? (The independent variable)
What will you measure? (The dependent variable)
How would you make it a fair test? (Controlled variables)
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
On a plain piece of paper add information from the following slides to create a mind map on iron including;
Alloying
Extraction
Properties
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
Most iron is converted into steels.
Removing all impurities would produce pure iron. Pure iron has a regular arrangement of atoms, with layers that can slide over each other, and so is soft and easily shaped, but too soft for many uses.
The iron collected from a blast furnace is only 96% pure.
molten iron
hot air
molten slag
raw materials
Usually, this product will be treated further because the impurities make iron brittle.
Teacher notes
See the ’Extracting Metals’ for more information about the blast furnace and reduction.
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
Steel is an alloy of iron and other elements, including carbon, nickel and chromium.
Steel is stronger than pure iron and can be used for everything from sauce pans…
…to suspension bridges!
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
The atoms of other elements are different sizes. When other elements are added to iron, their atoms distort the regular structure of the iron atoms.
The atoms in pure iron are arranged in densely-packed layers. These layers can slide over each other. This makes pure iron a very soft material.
It is more difficult for the layers of iron atoms in steel to slide over each other and so this alloy is stronger than pure iron.
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
OVERVIEW - Steel
Steels are alloys, since they are mixtures of iron with carbon and other metals. The different sized atoms distort the layers in the structure of the pure metal, making it more difficult for them to slide over each other, and so alloys are harder. Alloys can be designed to have properties for specific uses. Low carbon steels are easily shaped, high carbon steels are hard, and stainless steels are resistant to corrosion.
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
Steel is not a single substance & there are lots of different steels all being an alloy of iron with either carbon and/or other elements.
low carbon steel contains less than 0.25% carbon
Soft and easily shaped. Not as strong as high carbon steel but less likely to shatter.
high carbon steel contains more than 0.5% carbon.
Very strong but brittle.
1. CARBON STEEL: made by alloying Fe with small amounts of C (from 0.03-1.5%). They are the cheapest to make & are used for car bodies, knives, ships, machinery, containers, structural steel for buildings.
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
Nickel-steel very resistant to stretching forces so are used for long-span bridges, military armour-plating
Tungsten-steel operates well under very hot conditions so it is used to make high-speed tools.
2. LOW-ALLOY STEEL: made by alloying Fe with small amounts of other metals (from 1-5%). They are more expensive & may contain metals like Ni, Cr, Mn, V Ti and W. Each giving a different property.
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
Chromium-steel strong with chemical stability it is mixed with between 12-15% Cr and often some Ni
This is also known as ‘stainless steel’ These are used to make cooking utensils & cutlery, chemical reaction vessels because they combine hardness & strength with a resistance to corrosion (they do not rust!)
3. HIGH-ALLOY STEEL: made by alloying Fe with large amounts of other metals. They are EVEN more expensive & may contain metals like Ni, Cr, Mn, V Ti and W. Each giving a different property.
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
Photo credits
low carbon steel structure (small image only): © 2006 Jupiterimages Corporation
swords (small and large image): © 2006 Jupiterimages Corporation
stainless steel forks (small and large image): © 2006 Jupiterimages Corporation
aeroplane/shuttle image (small and large image): NASA
The space shuttle Discovery being transported from the NASA Dryden flight research centre to the Kennedy space centre, using a modified 747 aeroplane.
rotary blade (small and large image): © 2006 Jupiterimages Corporation
Teacher notes
This activity provides information about five important types of steel. The activity could be extended by asking students to suggest or research other types of steel.
37.unknown
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
Teacher notes
This matching activity can be used as a plenary or revision exercise on the uses of steel. Students could be asked to complete the activity in their books or using mini-whiteboards and the activity could be concluded by the completion on the IWB.
39.unknown
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
Ref’s Decision
If its true it stays, if its false SEND IT OFF!
Yellow = TRUE, Blue = FALSE
Steel is a mixture
Stainless steels are expensive
GCSE Core Chemistry
Exam tip; You DO need to know the 3 main types of steel (carbon, low-alloy & high-alloy) & identify what they contain
Learning Objectives:
By the end of the lesson I can:
• The properties of pig iron and how this limits its usefulness.
Pig iron is the intermediate product of smelting iron ore with coke. Pig iron has a very high carbon content, typically 3.5–4.5%, which makes it very brittle and not useful directly as a material except for limited applications.
• That iron can be alloyed to make it more useful.

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