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S4+S5 PURE CHEMISTRY🧪 > Metals > Flashcards

Metals Flashcards

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1
Q

Properties of metals

A

PHYSICAL
1. Good conductors of heat and electricity
2. High densities, melting points and boiling points
3. Malleable and ductile
CHEMICAL
1. Lose electrons to form positive ions in chemical reactions
2. Form ionic compounds with non-metals
3. React with oxygen to form basic or amphoteric oxides
4. React with dilute acids to form a salt and hydrogen

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2
Q

Why are pure metals not widely used in industry?

A
  1. Pure metals are soft. In a pure metal, the atoms are packed regularly in layers. The layers of atoms can slide over one another easily when a force is applied
  2. Pure metals may react with air and water and wear away or corrode easily
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3
Q

Why are metals often used as alloys?

A
  1. To make metals harder and stronger
  2. To improve the appearance of metals
  3. To lower the melting points of metals
  4. To make metals more resistant to corrosion
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4
Q

How to determine the order of reactivity series? Arrangement?

A
  1. Reaction of metals with cold water or steam
  2. Reaction of metals with dilute hydrochloric acid

In the reactivity series, metals are arranged from the most reactive to the least reactive

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5
Q

Reactivity series

A 
Potassium 
Sodium 
Calcium 
Magnesium 
Zinc 
Iron 
Lead
Hydrogen 
Copper
Silver
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6
Q

What are alloys?

A

A mixture of metals with one or a few other elements

STEEL
Iron, carbon
Harder and stronger than pure iron
higher carbon: construction 
lower carbon: making car bodies as they are more malleable
STAINLESS STEEL
Iron, carbon, chromium, nickel
Hard and resistant to corrosion 
Cutlery
SOLDER
Lead (70%), tin (30%)
low melting point 
Joining metals 
PEWTER
Lead (30%), tin (70%)
Does not corrode easily
Decorative ornaments
Brass
Copper, zinc
Hard and does not corrode easily
Musical instruments 
Bronze
Copper, tin
Hard and does not corrode easily
Medals
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7
Q

Reaction

A

metal + cold water —> metal hydroxide + hydrogen
metal + steam —> metal oxide + hydrogen
metal + dilute hydrochloric acid —> metal chloride + hydrogen

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8
Q

Observations of reactivity series for cold water

A 
POTASSIUM
Reacts very violently 
Enough heat is produced to cause hydrogen gas to ignite and explode
Lilac flame observed 
SODIUM
Reacts vigorously 
Hydrogen gas may ignite and catch fire
Yellow flame observed 
CALCIUM
Reacts readily/quickly
MAGNESIUM 
Reacts very slowly
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9
Q

Observations of reactivity series of steam

A 
POTASSIUM SODIUM CALCIUM 
Reacts violently and explosively
MAGNESIUM
Reacts vigorously 
A bright white glow is produced
A white solid is formed 
ZINC
Reacts readily
Forms yellow solid which turns white when cooled
IRON
Reacts slowly
A black solid is formed (iron(ii/iii) oxide)
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10
Q

Observations of reactivity series of dilute hydrochloric acid

A 
POTASSIUM SODIUM
Reacts violently and explosively 
Effervescence of colourless gas observed 
CALCIUM 
Reacts vigorously 
Effervescence of colourless gas observed 
MAGNESIUM 
Reacts rapidly
Effervescence of colourless gas observed
ZINC
Reacts moderately fast
Effervescence of colourless gas observed 
IRON
Reacts slowly
Slight effervescence of colourless gas observed 
LEAD
Reacts very slowly
No apparent reaction 
No bubbles in colourless gas observed
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11
Q

How to obtain metals from their ores? Methods? And which methods for what?

A
  1. Concentrating the metal ore
  2. Extracting crude metal from the ore
  3. Refining crude metal
  4. Reduction with carbon or carbon monoxide
  5. Electrolysis (Using electricity to decompose the molten ore to the metal)
  6. Occurs naturally uncombined
ELECTROLYSIS 
Potassium 
Sodium 
Calcium 
Magnesium 
Aluminium 
REDUCTION WITH CARBON OR CARBON MONOXIDE 
Zinc
Iron 
Lead
Copper
OCCURS NATURALLY UNCOMBINED
Silver
Gold
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12
Q

Blast furnace and haematite stuff

A

BLAST FURNACE
1. Carbon in coke reacts with oxygen from hot air to form carbon dioxide
2. Carbon dioxide that rises up the furnace reacts with coke to form carbon monoxide
3. Carbon monoxide reduces the iron(iii) oxide from haematite to form molten iron and carbon dioxide
Molten iron sinks to the bottom of the furnace
Carbon dioxide escapes as hot waste gases from the top of the furnace with nitrogen and carbon monoxide
4. Limestone that was added at the top of the furnace decomposes under heat to form calcium oxide and carbon dioxide
5. Calcium oxide reacts with sand to form molten slag
Slag is less dense than iron and floats on top of molten iron
High: slag
Low: iron

HAEMATITE
Coke
Iron(iii) oxide + impurities (sand +clay)
haematite + carbon monoxide —> iron + carbon dioxide

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13
Q

Rusting and Corrosion

A

RUSTING
The corrosion of iron
Presence of air (oxygen) and water
iron + water + oxygen —> hydrated iron(iii) oxide (rust)
CORROSION
The gradual destruction of any metal due to the reaction of water, air or other chemicals

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14
Q

Electroplating

A

Involves coating iron with a layer of another metal such as chromium, silver or copper, using electricity

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15
Q

Rust Preventions

A
  1. Painting
  2. Oiling or greasing
  3. Plastic coating
  4. Tin-plating
  5. Chrome-plating
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16
Q

Painting

A

Large objects like cars, ships and bridges

If the paint on the metal surface is scratched, rusting takes place under the painted surface

17
Q

Oiling or greasing

A

Tools and machine parts

The protective film or oil or grease gathers dust and must be renewed

18
Q

Plastic coating

A

Kitchenware such as draining racks

If the plastic layer is torn, the iron starts to rust

19
Q

Tin-plating

A

Food cans

If the tin layer is scratched, the iron beneath it rusts

20
Q

Chrome-plating

A

Taps, kettles and bicycle handle bars

This gives a bright shiny finish, as well as rust protection

21
Q

Coke function

A

Make carbon monoxide reduce the iron ore

22
Q

Limestone function

A

To convert impurities in the ore into slag

23
Q

Advantages of recycling metals

A
  1. Conserve finite metal resources
  2. Reduce environmental problems caused by extraction of metals and disposal of waste metals
  3. Saves the cost of extracting metals
24
Q

Disadvantages of recycling metals

A
  1. Recycling can be more costly than extracting metals directly from their ores
  2. Takes time and effort to educate businesses and communities to practice recycling as a way of life
  3. Causes pollution problems
25
Q

Why are alloys harder and stronger than constituent pure metals

A

Pure metals consists of atoms of the same size which are arranged in an orderly manner. When a force is applied, the layers of atoms can slide across each other easily. In an alloy, the different size of atoms from other atoms disrupts the orderly arrangement of the atoms, preventing them from sliding over each other easily. This make alloys harder and stronger

S4+S5 PURE CHEMISTRY🧪 (8 decks)

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